Granites are nearly absent in the Solar System outside of Earth. Achieving granitic
compositions in magmatic systems requires multi-stage melting and fractionation,
which also increases the concentration of radiogenic elements1
. Abundant water and
plate tectonics facilitate these processes on Earth, aiding in remelting. Although these
drivers are absent on the Moon, small granite samples have been found, but details
of their origin and the scale of systems they represent are unknown2
. Here we report
microwave-wavelength measurements of an anomalously hot geothermal source that
is best explained by the presence of an approximately 50-kilometre-diameter granitic
system below the thorium-rich farside feature known as Compton–Belkovich. Passive
microwave radiometry is sensitive to the integrated thermal gradient to several
wavelengths depth. The 3–37-gigahertz antenna temperatures of the Chang’e-1 and
Chang’e-2 microwave instruments allow us to measure a peak heat fux of about
180 milliwatts per square metre, which is about 20 times higher than that of the
average lunar highlands3,4
. The surprising magnitude and geographic extent of this
feature imply an Earth-like, evolved granitic system larger than believed possible on
the Moon, especially outside of the Procellarum region5
. Furthermore, these methods
are generalizable: similar uses of passive radiometric data could vastly expand our
knowledge of geothermal processes on the Moon and other planetary bodies.
Interchange reconnection as the source of the fast solar wind within coronal ...Sérgio Sacani
1) Recent measurements from Parker Solar Probe showed that the fast solar wind emerging from coronal holes is organized into 'microstreams' with an angular scale similar to underlying supergranulation cells associated with horizontal flows in the photosphere.
2) During a solar encounter where Parker Solar Probe came within 12.3 solar radii of the photosphere, plasma, energetic ion, and magnetic field measurements showed discrete microstreams structured at scales of supergranulation, with associated switchbacks of the radial magnetic field.
3) Correlation of the microstream and switchback structure with the spatial periodicity of the surface magnetic field suggests that interchange reconnection between open and closed magnetic fields in the low corona is driving the bursts observed by
Observation of Bose–Einstein condensates in an Earth-orbiting research labSérgio Sacani
Quantum mechanics governs the microscopic world, where low mass and momentum
reveal a natural wave–particle duality. Magnifying quantum behaviour to
macroscopic scales is a major strength of the technique of cooling and trapping
atomic gases, in which low momentum is engineered through extremely low
temperatures. Advances in this feld have achieved such precise control over atomic
systems that gravity, often negligible when considering individual atoms, has
emerged as a substantial obstacle. In particular, although weaker trapping felds
would allow access to lower temperatures1,2
, gravity empties atom traps that are too
weak. Additionally, inertial sensors based on cold atoms could reach better
sensitivities if the free-fall time of the atoms after release from the trap could be made
longer3
. Planetary orbit, specifcally the condition of perpetual free-fall, ofers to lift
cold-atom studies beyond such terrestrial limitations. Here we report production of
rubidium Bose–Einstein condensates (BECs) in an Earth-orbiting research laboratory,
the Cold Atom Lab. We observe subnanokelvin BECs in weak trapping potentials with
free-expansion times extending beyond one second, providing an initial
demonstration of the advantages ofered by a microgravity environment for
cold-atom experiments and verifying the successful operation of this facility. With
routine BEC production, continuing operations will support long-term investigations
of trap topologies unique to microgravity4,5
, atom-laser sources6
, few-body physics7,8
and pathfnding techniques for atom-wave interferometry9–12
Formation of lunar surface water associated with high-energy electrons in Ear...Sérgio Sacani
Solar wind implantation is thought to be one of the primary mechanisms in
the formation of water (OH/H2O) on the surface of the Moon and possibly
on the surface of other airless bodies. The lunar nearside spends ~27% of
its daytime in Earth’s magnetotail where the solar wind flux is reduced
by as much as ~99%. However, no correlated decrease in surficial water
content has yet been seen on the lunar nearside. Here we report abundance
observations of lunar surficial water on the nearside at different stages
during the Moon’s passage through Earth’s magnetotail. We find that the
water abundance at lunar mid-latitudes substantially increases in the dusk
and dawn magnetosheath when the solar wind flux increases, yet remains
nearly constant across the central magnetotail. We suggest that although
we have confirmed the importance of the solar wind as a major source of
fast water production on the Moon, hitherto unobserved properties of the
plasma sheet properties may also play an important role.
1. Controlled-source electromagnetic (CSEM) and magnetotelluric profiling (MT) are two key geophysical methods that use electromagnetic waves for offshore oil exploration. CSEM works by transmitting low frequency EM waves from a source and analyzing the resistivity contrasts in the subsurface based on readings from receiver arrays. MT uses a broader range of frequencies over time to create a smooth profile of the subsurface that accounts for anisotropic properties.
2. While CSEM is better for exploring a large area due to its deep penetration, MT provides more accurate detail on the orientation and location of reservoirs due to its consideration of anisotropy. Together, the methods can complement each other in offshore oil exploration.
Every second greater than 1025 antineutrinos radiate to space from Earth, shining like a faint antineutrino
star. Underground antineutrino detectors have revealed the rapidly decaying fission products inside
nuclear reactors, verified the long-lived radioactivity inside our planet, and informed sensitive
experiments for probing fundamental physics. Mapping the anisotropic antineutrino flux and energy
spectrum advance geoscience by defining the amount and distribution of radioactive power within Earth
while critically evaluating competing compositional models of the planet. We present the Antineutrino
Global Map 2015 (AGM2015), an experimentally informed model of Earth’s surface antineutrino flux over
the 0 to 11MeV energy spectrum, along with an assessment of systematic errors. The open source
AGM2015 provides fundamental predictions for experiments, assists in strategic detector placement to
determine neutrino mass hierarchy, and aids in identifying undeclared nuclear reactors. We use
cosmochemically and seismologically informed models of the radiogenic lithosphere/mantle combined
with the estimated antineutrino flux, as measured by KamLAND and Borexino, to determine the Earth’s
total antineutrino luminosity at . × / ν .
.
−
+ 3 4 10 s 2 2
2 3 25
e . We find a dominant flux of geo-neutrinos, predict
sub-equal crust and mantle contributions, with ~1% of the total flux from man-made nuclear reactors.
Mars surface radiation_environment_measured_with_curiositySérgio Sacani
The Radiation Assessment Detector on the Curiosity rover measured the radiation environment on the surface of Mars over approximately 300 days. It found:
1) The average absorbed radiation dose from galactic cosmic rays was 0.210 mGy/day, varying due to atmospheric and solar conditions.
2) An additional absorbed dose of about 50 μGy was measured from a solar particle event.
3) Extrapolating the surface measurements, the absorbed dose was estimated to be 76 mGy/year at 1 meter below the surface, decreasing substantially at greater depths.
Venus and Earth have remarkably diferent
surface conditions, yet the lithospheric
thickness and heat fow on Venus may be
Earth-like. This fnding supports a tectonic
regime with limited surface mobility and
dominated by intrusive magmatism.
Interchange reconnection as the source of the fast solar wind within coronal ...Sérgio Sacani
1) Recent measurements from Parker Solar Probe showed that the fast solar wind emerging from coronal holes is organized into 'microstreams' with an angular scale similar to underlying supergranulation cells associated with horizontal flows in the photosphere.
2) During a solar encounter where Parker Solar Probe came within 12.3 solar radii of the photosphere, plasma, energetic ion, and magnetic field measurements showed discrete microstreams structured at scales of supergranulation, with associated switchbacks of the radial magnetic field.
3) Correlation of the microstream and switchback structure with the spatial periodicity of the surface magnetic field suggests that interchange reconnection between open and closed magnetic fields in the low corona is driving the bursts observed by
Observation of Bose–Einstein condensates in an Earth-orbiting research labSérgio Sacani
Quantum mechanics governs the microscopic world, where low mass and momentum
reveal a natural wave–particle duality. Magnifying quantum behaviour to
macroscopic scales is a major strength of the technique of cooling and trapping
atomic gases, in which low momentum is engineered through extremely low
temperatures. Advances in this feld have achieved such precise control over atomic
systems that gravity, often negligible when considering individual atoms, has
emerged as a substantial obstacle. In particular, although weaker trapping felds
would allow access to lower temperatures1,2
, gravity empties atom traps that are too
weak. Additionally, inertial sensors based on cold atoms could reach better
sensitivities if the free-fall time of the atoms after release from the trap could be made
longer3
. Planetary orbit, specifcally the condition of perpetual free-fall, ofers to lift
cold-atom studies beyond such terrestrial limitations. Here we report production of
rubidium Bose–Einstein condensates (BECs) in an Earth-orbiting research laboratory,
the Cold Atom Lab. We observe subnanokelvin BECs in weak trapping potentials with
free-expansion times extending beyond one second, providing an initial
demonstration of the advantages ofered by a microgravity environment for
cold-atom experiments and verifying the successful operation of this facility. With
routine BEC production, continuing operations will support long-term investigations
of trap topologies unique to microgravity4,5
, atom-laser sources6
, few-body physics7,8
and pathfnding techniques for atom-wave interferometry9–12
Formation of lunar surface water associated with high-energy electrons in Ear...Sérgio Sacani
Solar wind implantation is thought to be one of the primary mechanisms in
the formation of water (OH/H2O) on the surface of the Moon and possibly
on the surface of other airless bodies. The lunar nearside spends ~27% of
its daytime in Earth’s magnetotail where the solar wind flux is reduced
by as much as ~99%. However, no correlated decrease in surficial water
content has yet been seen on the lunar nearside. Here we report abundance
observations of lunar surficial water on the nearside at different stages
during the Moon’s passage through Earth’s magnetotail. We find that the
water abundance at lunar mid-latitudes substantially increases in the dusk
and dawn magnetosheath when the solar wind flux increases, yet remains
nearly constant across the central magnetotail. We suggest that although
we have confirmed the importance of the solar wind as a major source of
fast water production on the Moon, hitherto unobserved properties of the
plasma sheet properties may also play an important role.
1. Controlled-source electromagnetic (CSEM) and magnetotelluric profiling (MT) are two key geophysical methods that use electromagnetic waves for offshore oil exploration. CSEM works by transmitting low frequency EM waves from a source and analyzing the resistivity contrasts in the subsurface based on readings from receiver arrays. MT uses a broader range of frequencies over time to create a smooth profile of the subsurface that accounts for anisotropic properties.
2. While CSEM is better for exploring a large area due to its deep penetration, MT provides more accurate detail on the orientation and location of reservoirs due to its consideration of anisotropy. Together, the methods can complement each other in offshore oil exploration.
Every second greater than 1025 antineutrinos radiate to space from Earth, shining like a faint antineutrino
star. Underground antineutrino detectors have revealed the rapidly decaying fission products inside
nuclear reactors, verified the long-lived radioactivity inside our planet, and informed sensitive
experiments for probing fundamental physics. Mapping the anisotropic antineutrino flux and energy
spectrum advance geoscience by defining the amount and distribution of radioactive power within Earth
while critically evaluating competing compositional models of the planet. We present the Antineutrino
Global Map 2015 (AGM2015), an experimentally informed model of Earth’s surface antineutrino flux over
the 0 to 11MeV energy spectrum, along with an assessment of systematic errors. The open source
AGM2015 provides fundamental predictions for experiments, assists in strategic detector placement to
determine neutrino mass hierarchy, and aids in identifying undeclared nuclear reactors. We use
cosmochemically and seismologically informed models of the radiogenic lithosphere/mantle combined
with the estimated antineutrino flux, as measured by KamLAND and Borexino, to determine the Earth’s
total antineutrino luminosity at . × / ν .
.
−
+ 3 4 10 s 2 2
2 3 25
e . We find a dominant flux of geo-neutrinos, predict
sub-equal crust and mantle contributions, with ~1% of the total flux from man-made nuclear reactors.
Mars surface radiation_environment_measured_with_curiositySérgio Sacani
The Radiation Assessment Detector on the Curiosity rover measured the radiation environment on the surface of Mars over approximately 300 days. It found:
1) The average absorbed radiation dose from galactic cosmic rays was 0.210 mGy/day, varying due to atmospheric and solar conditions.
2) An additional absorbed dose of about 50 μGy was measured from a solar particle event.
3) Extrapolating the surface measurements, the absorbed dose was estimated to be 76 mGy/year at 1 meter below the surface, decreasing substantially at greater depths.
Venus and Earth have remarkably diferent
surface conditions, yet the lithospheric
thickness and heat fow on Venus may be
Earth-like. This fnding supports a tectonic
regime with limited surface mobility and
dominated by intrusive magmatism.
This document describes experiments simulating volcanic flooding on the Moon using lunar topography data. Three similarly sized regions were artificially flooded: 1) heavily cratered terrain, 2) Hertzsprung basin, and 3) the Central Highlands. As flooding progressed, small craters were buried first followed by larger craters. Comparing the results from point source and ubiquitous flooding showed little difference in the volume of lava added or changes to crater size distributions over time. The experiments provide insights into estimating lava volumes involved in large scale resurfacing events on terrestrial planets.
The solar dynamo begins near the surfaceSérgio Sacani
The magnetic dynamo cycle of the Sun features a distinct pattern: a propagating
region of sunspot emergence appears around 30° latitude and vanishes near the
equator every 11 years (ref. 1). Moreover, longitudinal flows called torsional oscillations
closely shadow sunspot migration, undoubtedly sharing a common cause2. Contrary
to theories suggesting deep origins of these phenomena, helioseismology pinpoints
low-latitude torsional oscillations to the outer 5–10% of the Sun, the near-surface
shear layer3,4. Within this zone, inwardly increasing differential rotation coupled with
a poloidal magnetic field strongly implicates the magneto-rotational instability5,6,
prominent in accretion-disk theory and observed in laboratory experiments7.
Together, these two facts prompt the general question: whether the solar dynamo is
possibly a near-surface instability. Here we report strong affirmative evidence in stark
contrast to traditional models8 focusing on the deeper tachocline. Simple analytic
estimates show that the near-surface magneto-rotational instability better explains
the spatiotemporal scales of the torsional oscillations and inferred subsurface
magnetic field amplitudes9. State-of-the-art numerical simulations corroborate these
estimates and reproduce hemispherical magnetic current helicity laws10. The dynamo
resulting from a well-understood near-surface phenomenon improves prospects
for accurate predictions of full magnetic cycles and space weather, affecting the
electromagnetic infrastructure of Earth.
This document summarizes research analyzing data from the Van Allen Probes and BARREL (Balloon Array for Radiation Belt Relativistic Electron Losses) campaigns to further understand global coherence in radiation belt electron loss modulated by plasmaspheric hiss. Analysis of data from 71 balloon payload combinations found significant coherence around noon, likely caused by solar wind structures impacting the bow shock and creating compressional waves propagating through the magnetosphere. This research aims to better understand how ultra-low frequency waves originating in the solar wind can cause nearly global-scale coherence in electron loss.
This document compares the statistical properties of solar flares and earthquakes by analyzing event energy distributions, time series, and interevent times from solar flare and earthquake catalogs. It finds that the two phenomena exhibit different scaling statistics, and the same phenomenon observed in different periods or locations cannot be uniformly scaled to a single distribution. This suggests an apparent complexity in impulsive energy release processes that does not follow a common behavior attributable to a universal physical mechanism.
Evidence for the_thermal_sunyaev-zeldovich_effect_associated_with_quasar_feed...Sérgio Sacani
Using a radio-quiet subsample of the Sloan Digital Sky Survey spectroscopic quasar
catalogue, spanning redshifts 0.5–3.5, we derive the mean millimetre and far-infrared
quasar spectral energy distributions (SEDs) via a stacking analysis of Atacama Cosmology
Telescope and Herschel-Spectral and Photometric Imaging REceiver data. We
constrain the form of the far-infrared emission and find 3σ–4σ evidence for the thermal
Sunyaev-Zel’dovich (SZ) effect, characteristic of a hot ionized gas component with
thermal energy (6.2 ± 1.7) × 1060 erg. This amount of thermal energy is greater than
expected assuming only hot gas in virial equilibrium with the dark matter haloes of
(1 − 5) × 1012h
−1M that these systems are expected to occupy, though the highest
quasar mass estimates found in the literature could explain a large fraction of this
energy. Our measurements are consistent with quasars depositing up to (14.5±3.3) τ
−1
8
per cent of their radiative energy into their circumgalactic environment if their typical
period of quasar activity is τ8 × 108 yr. For high quasar host masses, ∼ 1013h
−1M,
this percentage will be reduced. Furthermore, the uncertainty on this percentage is
only statistical and additional systematic uncertainties enter at the 40 per cent level.
The SEDs are dust dominated in all bands and we consider various models for dust
emission. While sufficiently complex dust models can obviate the SZ effect, the SZ
interpretation remains favoured at the 3σ–4σ level for most models.
Thermonuclear explosions on neutron stars reveal the speed of their jetsSérgio Sacani
Relativistic jets are observed from accreting and cataclysmic transients throughout
the Universe, and have a profound impact on their surroundings1,2
. Despite their
importance, their launch mechanism is not known. For accreting neutron stars, the
speed of their compact jets can reveal whether the jets are powered by magnetic felds
anchored in the accretion fow3
or in the star itself 4,5
, but so far no such measurements
exist. These objects can show bright explosions on their surface due to unstable
thermonuclear burning of recently accreted material, called type-I X-ray bursts6
,
during which the mass-accretion rate increases7–9
. Here, we report on bright fares in
the jet emission for a few minutes after each X-ray burst, attributed to the increased
accretion rate. With these fares, we measure the speed of a neutron star compact jet
to be v c = 0.38−0.08
+0.11 , much slower than those from black holes at similar luminosities.
This discovery provides a powerful new tool in which we can determine the role that
individual system properties have on the jet speed, revealing the dominant jet
launching mechanism.
1) Global climate models that include sophisticated cloud schemes show that tidally locked planets can develop thick water clouds near the substellar point due to strong convection. These clouds greatly increase the planetary albedo and stabilize temperatures, allowing habitability at twice the stellar flux previously thought possible.
2) The cloud feedback is stabilizing, as higher stellar flux produces stronger convection and higher albedos. Substellar clouds can block outgoing radiation, reducing the day-night temperature contrast.
3) Non-tidally locked planets do not experience this stabilizing cloud feedback, as clouds only form over parts of the tropics and mid-latitudes. Their albedo decreases with increasing stellar flux, producing a destabil
Earth-like lithospheric thickness and heat flow on Venus consistent with acti...Sérgio Sacani
Venus is Earth’s twin in size and radiogenic heat budget, yet it remains
unclear how Venus loses its heat absent plate tectonics. Most Venusian
stagnant-lid models predict a thick lithosphere with heat fow about half
that of Earth’s mobile-lid regime. Here we estimate elastic lithospheric
thickness at 75 locations on Venus using topographic fexure at 65 coronae—
quasi-circular volcano-tectonic features—determined from Magellan
altimetry data. We fnd an average thickness at coronae of 11 ± 7 km. This
implies an average heat fow of 101 ± 88 mW m−2, higher than Earth’ s
average but similar to terrestrial values in actively extending areas. For
some locations, such as the Parga Chasma rift zone, we estimate heat fow
exceeding 75 mW m−2. Combined with a low-resolution map of global elastic
thickness, this suggests that coronae typically form on thin lithosphere,
instead of locally thinning the lithosphere via plume heating, and that most
regions of low elastic thickness are best explained by high heat fow rather
than crustal compensation. Our analysis identifes likely areas of active
extension and suggests that Venus has Earth-like lithospheric thickness
and global heat fow ranges. Together with the planet’s geologic history,
our fndings support a squishy-lid convective regime that relies on plumes,
intrusive magmatism and delamination to increase heat fow.
Melting curve of superionic ammonia at planetary interior conditionsSérgio Sacani
Under high pressures and temperatures, molecular systems with substantial
polarization charges, such as ammonia and water, are predicted to form
superionic phases and dense fluid states with dissociating molecules
and high electrical conductivity. This behaviour potentially plays a role
in explaining the origin of the multipolar magnetic fields of Uranus and
Neptune, whose mantles are thought to result from a mixture of H2O, NH3
and CH4 ices. Determining the stability domain, melting curve and electrical
conductivity of these superionic phases is therefore crucial for modelling
planetary interiors and dynamos. Here we report the melting curve of
superionic ammonia up to 300 GPa from laser-driven shock compression
of pre-compressed samples and atomistic calculations. We show that
ammonia melts at lower temperatures than water above 100 GPa and that
fluid ammonia’s electrical conductivity exceeds that of water at conditions
predicted by hot, super-adiabatic models for Uranus and Neptune, and
enhances the conductivity in their fluid water-rich dynamo layers.
This document summarizes simulations of graphene growth on a copper substrate. Monte Carlo simulations were performed on a honeycomb lattice with various levels of static and dynamic substrate disorder. For static disorder, carbon atoms reside on favorable substrate sites, reducing mobility and resulting in smaller islands. For dynamic disorder, the changing substrate allows islands to move and reform, enhancing island size at optimal temperatures. The substrate itself shows no ordering without carbon islands at high dynamic disorder temperatures.
The document presents evidence for azimuthal variations in cosmic ray ion acceleration at the blast wave of the supernova remnant SN 1006. Using radio, X-ray, and optical observations, the researchers find that the ratio of radii between the blast wave and contact discontinuity varies azimuthally, being smallest in the brightest synchrotron emission regions, indicating more efficient cosmic ray acceleration. They interpret this as evidence that the injection rate, magnetic field strength, and turbulence level - which influence cosmic ray acceleration - all vary azimuthally and are highest in the brightest regions.
This document discusses evidence that the Moon-forming impact occurred later than previously thought, at around 95 million years after the formation of the solar system. The study uses simulations of planetary formation to show a correlation between the timing of the last giant impact and the amount of mass later accreted by the planet. Comparing this to highly siderophile element abundances in Earth's mantle, which constrain the amount of late-accreted mass, the study determines the Moon-forming impact was most likely 95 million years after solar system formation. Earlier times of 40 million years or less are ruled out at a 99.9% confidence level. The simulations include both classical scenarios and scenarios where Jupiter and Saturn migrated inward early in the solar
We investigate a variety of short warning time, terminal mitigation scenarios via
fragmentation for a hypothetical impact of asteroid 2023 NT1, a Near-Earth Object (NEO) that
was discovered on July 15, 2023, two days after its closest approach to Earth on July 13. The
asteroid passed by Earth within ~0.25 lunar distances with a closest approach distance of ~105
km and speed of 11.27 km/s. Its size remains largely uncertain, with an estimated diameter range
of 26 – 58 m and probable diameter estimate (weighted by the NEO size frequency distribution)
of 34 m (JPL Sentry, September 12, 2023). The asteroid approached Earth from the direction of
the Sun, as did both the Chelyabinsk asteroid in 2013 and comet NEOWISE in 2021. As a result,
2023 NT1 remained undetected until after its closest approach. If it had been on a collision
course, it would have had an impact energy of ~1.5 Mt (assuming a spherical asteroid with the
probable diameter estimate of 34 m, 2.6 g/cm3 uniform density, and impact speed of 15.59 km/s).
2023 NT1 represents a threat that could have caused significant local damage (~3x Chelyabinsk
airburst energy). We utilize the PI (“Pulverize It”) method for planetary defense to model
potential mitigation scenarios of an object like 2023 NT1 through simulations of hypervelocity
asteroid disruption and atmospheric ground effects for the case of a terminal defense mode.
Simulations suggest that PI is an effective multimodal approach for planetary defense that can
operate in extremely short interdiction modes (with intercepts as short as hours prior to impact),
in addition to long interdiction time scales with months to years of warning. Our simulations
support the proposition that threats like 2023 NT1 can be effectively mitigated with intercepts of
one day (or less) prior to impact, yielding minimal to no ground damage, using modest resources
and existing technologies.
Web science emerged as a new interdisciplinary field to study and understand the World Wide Web. It aims to:
1) Model the Web's structure as a scale-free network and understand the architectural principles that fueled its growth.
2) Discover how online human interactions are driven by social conventions and how these interactions shape emergent properties like social networking and online communities.
3) Develop approaches to harness the Web's positive potential while addressing issues like privacy, security, and intellectual property through technical and policy solutions.
Major universities have established the Web Science Research Initiative to advance this new field through research collaborations, publications, and conferences. Important insights into search algorithms, network structure, and online behavior
This document discusses how geomagnetic storms can affect marine archaeological surveys by introducing noise and masking spatial variations in Earth's magnetic field that are used to identify archaeological anomalies. The study analyzed 34 geomagnetic storms and found that their sudden onset signatures were indistinguishable from archaeological anomalies. Based on this, it is estimated that 89.7-100% of strong geomagnetic storms will generate signatures that could be misinterpreted as archaeological sites. The document recommends improved data collection and processing methods to better account for geomagnetic storms and improve precision in identifying archaeological resources.
Detection of an atmosphere around the super earth 55 cancri eSérgio Sacani
We report the analysis of two new spectroscopic observations of the super-Earth 55 Cancri e, in the near
infrared, obtained with the WFC3 camera onboard the HST. 55 Cancri e orbits so close to its parent
star, that temperatures much higher than 2000 K are expected on its surface. Given the brightness
of 55 Cancri, the observations were obtained in scanning mode, adopting a very long scanning length
and a very high scanning speed. We use our specialized pipeline to take into account systematics
introduced by these observational parameters when coupled with the geometrical distortions of the
instrument. We measure the transit depth per wavelength channel with an average relative uncertainty
of 22 ppm per visit and nd modulations that depart from a straight line model with a 6 condence
level. These results suggest that 55 Cancri e is surrounded by an atmosphere, which is probably
hydrogen-rich. Our fully Bayesian spectral retrieval code, T -REx, has identied HCN to be the
most likely molecular candidate able to explain the features at 1.42 and 1.54 m. While additional
spectroscopic observations in a broader wavelength range in the infrared will be needed to conrm
the HCN detection, we discuss here the implications of such result. Our chemical model, developed
with combustion specialists, indicates that relatively high mixing ratios of HCN may be caused by a
high C/O ratio. This result suggests this super-Earth is a carbon-rich environment even more exotic
than previously thought.
- The document discusses two potential causes of the mass extinction event that wiped out the dinosaurs - massive volcanic activity from the Deccan Traps (in present-day India), and a large asteroid impact in what is now the Gulf of Mexico.
- Through climate and habitat modeling, the researchers found that scenarios involving prolonged global cooling from the asteroid impact led to a substantial reduction in suitable habitats for dinosaurs worldwide.
- In contrast, simulations of Deccan volcanism, even those with major global warming effects from carbon dioxide release, did not produce conditions severe enough to cause a dinosaur extinction.
- The asteroid impact may have been the primary driver of the non-avian dinosaur extinction, though volcanic warming likely reduced
THE IMPORTANCE OF MARTIAN ATMOSPHERE SAMPLE RETURN.Sérgio Sacani
The return of a sample of near-surface atmosphere from Mars would facilitate answers to several first-order science questions surrounding the formation and evolution of the planet. One of the important aspects of terrestrial planet formation in general is the role that primary atmospheres played in influencing the chemistry and structure of the planets and their antecedents. Studies of the martian atmosphere can be used to investigate the role of a primary atmosphere in its history. Atmosphere samples would also inform our understanding of the near-surface chemistry of the planet, and ultimately the prospects for life. High-precision isotopic analyses of constituent gases are needed to address these questions, requiring that the analyses are made on returned samples rather than in situ.
Filamentary structures as the origin of blazar jet radio variabilitySérgio Sacani
Supermassive black holes at the centre of active galactic nuclei power some
of the most luminous objects in the Universe. Typically, very-long-baseline
interferometric observations of blazars have revealed only funnel-like
morphologies with little information on the internal structure of the ejected
plasma or have lacked the dynamic range to reconstruct the extended jet
emission. Here we present microarcsecond-scale angular resolution images
of the blazar 3C 279 obtained at 22 GHz with the space very-long-baseline
interferometry mission RadioAstron, which allowed us to resolve the jet
transversely and reveal several flaments produced by plasma instabilities
in a kinetically dominated fow. The polarimetric properties derived
from our high-angular-resolution and broad-dynamic-range images are
consistent with the presence of a helical magnetic feld threaded to the jet.
We infer a clockwise rotation as seen in the direction of fow motion with an
intrinsic helix pitch angle of ~45° and a Lorentz factor of ~13 at the time of
observation. We also propose a model to explain blazar jet radio variability
in which emission features travelling down the jet may manifest as a result
of diferential Doppler boosting within the flaments, as opposed to the
standard shock-in-jet model. Characterizing such variability is particularly
important given the relevance of blazar physics from cosmic particle
acceleration to standard candles in cosmology.
The binding of cosmological structures by massless topological defectsSérgio Sacani
Assuming spherical symmetry and weak field, it is shown that if one solves the Poisson equation or the Einstein field
equations sourced by a topological defect, i.e. a singularity of a very specific form, the result is a localized gravitational
field capable of driving flat rotation (i.e. Keplerian circular orbits at a constant speed for all radii) of test masses on a thin
spherical shell without any underlying mass. Moreover, a large-scale structure which exploits this solution by assembling
concentrically a number of such topological defects can establish a flat stellar or galactic rotation curve, and can also deflect
light in the same manner as an equipotential (isothermal) sphere. Thus, the need for dark matter or modified gravity theory is
mitigated, at least in part.
EWOCS-I: The catalog of X-ray sources in Westerlund 1 from the Extended Weste...Sérgio Sacani
Context. With a mass exceeding several 104 M⊙ and a rich and dense population of massive stars, supermassive young star clusters
represent the most massive star-forming environment that is dominated by the feedback from massive stars and gravitational interactions
among stars.
Aims. In this paper we present the Extended Westerlund 1 and 2 Open Clusters Survey (EWOCS) project, which aims to investigate
the influence of the starburst environment on the formation of stars and planets, and on the evolution of both low and high mass stars.
The primary targets of this project are Westerlund 1 and 2, the closest supermassive star clusters to the Sun.
Methods. The project is based primarily on recent observations conducted with the Chandra and JWST observatories. Specifically,
the Chandra survey of Westerlund 1 consists of 36 new ACIS-I observations, nearly co-pointed, for a total exposure time of 1 Msec.
Additionally, we included 8 archival Chandra/ACIS-S observations. This paper presents the resulting catalog of X-ray sources within
and around Westerlund 1. Sources were detected by combining various existing methods, and photon extraction and source validation
were carried out using the ACIS-Extract software.
Results. The EWOCS X-ray catalog comprises 5963 validated sources out of the 9420 initially provided to ACIS-Extract, reaching a
photon flux threshold of approximately 2 × 10−8 photons cm−2
s
−1
. The X-ray sources exhibit a highly concentrated spatial distribution,
with 1075 sources located within the central 1 arcmin. We have successfully detected X-ray emissions from 126 out of the 166 known
massive stars of the cluster, and we have collected over 71 000 photons from the magnetar CXO J164710.20-455217.
Weitere ähnliche Inhalte
Ähnlich wie Remote detection of a lunar granitic batholith at Compton–Belkovich
This document describes experiments simulating volcanic flooding on the Moon using lunar topography data. Three similarly sized regions were artificially flooded: 1) heavily cratered terrain, 2) Hertzsprung basin, and 3) the Central Highlands. As flooding progressed, small craters were buried first followed by larger craters. Comparing the results from point source and ubiquitous flooding showed little difference in the volume of lava added or changes to crater size distributions over time. The experiments provide insights into estimating lava volumes involved in large scale resurfacing events on terrestrial planets.
The solar dynamo begins near the surfaceSérgio Sacani
The magnetic dynamo cycle of the Sun features a distinct pattern: a propagating
region of sunspot emergence appears around 30° latitude and vanishes near the
equator every 11 years (ref. 1). Moreover, longitudinal flows called torsional oscillations
closely shadow sunspot migration, undoubtedly sharing a common cause2. Contrary
to theories suggesting deep origins of these phenomena, helioseismology pinpoints
low-latitude torsional oscillations to the outer 5–10% of the Sun, the near-surface
shear layer3,4. Within this zone, inwardly increasing differential rotation coupled with
a poloidal magnetic field strongly implicates the magneto-rotational instability5,6,
prominent in accretion-disk theory and observed in laboratory experiments7.
Together, these two facts prompt the general question: whether the solar dynamo is
possibly a near-surface instability. Here we report strong affirmative evidence in stark
contrast to traditional models8 focusing on the deeper tachocline. Simple analytic
estimates show that the near-surface magneto-rotational instability better explains
the spatiotemporal scales of the torsional oscillations and inferred subsurface
magnetic field amplitudes9. State-of-the-art numerical simulations corroborate these
estimates and reproduce hemispherical magnetic current helicity laws10. The dynamo
resulting from a well-understood near-surface phenomenon improves prospects
for accurate predictions of full magnetic cycles and space weather, affecting the
electromagnetic infrastructure of Earth.
This document summarizes research analyzing data from the Van Allen Probes and BARREL (Balloon Array for Radiation Belt Relativistic Electron Losses) campaigns to further understand global coherence in radiation belt electron loss modulated by plasmaspheric hiss. Analysis of data from 71 balloon payload combinations found significant coherence around noon, likely caused by solar wind structures impacting the bow shock and creating compressional waves propagating through the magnetosphere. This research aims to better understand how ultra-low frequency waves originating in the solar wind can cause nearly global-scale coherence in electron loss.
This document compares the statistical properties of solar flares and earthquakes by analyzing event energy distributions, time series, and interevent times from solar flare and earthquake catalogs. It finds that the two phenomena exhibit different scaling statistics, and the same phenomenon observed in different periods or locations cannot be uniformly scaled to a single distribution. This suggests an apparent complexity in impulsive energy release processes that does not follow a common behavior attributable to a universal physical mechanism.
Evidence for the_thermal_sunyaev-zeldovich_effect_associated_with_quasar_feed...Sérgio Sacani
Using a radio-quiet subsample of the Sloan Digital Sky Survey spectroscopic quasar
catalogue, spanning redshifts 0.5–3.5, we derive the mean millimetre and far-infrared
quasar spectral energy distributions (SEDs) via a stacking analysis of Atacama Cosmology
Telescope and Herschel-Spectral and Photometric Imaging REceiver data. We
constrain the form of the far-infrared emission and find 3σ–4σ evidence for the thermal
Sunyaev-Zel’dovich (SZ) effect, characteristic of a hot ionized gas component with
thermal energy (6.2 ± 1.7) × 1060 erg. This amount of thermal energy is greater than
expected assuming only hot gas in virial equilibrium with the dark matter haloes of
(1 − 5) × 1012h
−1M that these systems are expected to occupy, though the highest
quasar mass estimates found in the literature could explain a large fraction of this
energy. Our measurements are consistent with quasars depositing up to (14.5±3.3) τ
−1
8
per cent of their radiative energy into their circumgalactic environment if their typical
period of quasar activity is τ8 × 108 yr. For high quasar host masses, ∼ 1013h
−1M,
this percentage will be reduced. Furthermore, the uncertainty on this percentage is
only statistical and additional systematic uncertainties enter at the 40 per cent level.
The SEDs are dust dominated in all bands and we consider various models for dust
emission. While sufficiently complex dust models can obviate the SZ effect, the SZ
interpretation remains favoured at the 3σ–4σ level for most models.
Thermonuclear explosions on neutron stars reveal the speed of their jetsSérgio Sacani
Relativistic jets are observed from accreting and cataclysmic transients throughout
the Universe, and have a profound impact on their surroundings1,2
. Despite their
importance, their launch mechanism is not known. For accreting neutron stars, the
speed of their compact jets can reveal whether the jets are powered by magnetic felds
anchored in the accretion fow3
or in the star itself 4,5
, but so far no such measurements
exist. These objects can show bright explosions on their surface due to unstable
thermonuclear burning of recently accreted material, called type-I X-ray bursts6
,
during which the mass-accretion rate increases7–9
. Here, we report on bright fares in
the jet emission for a few minutes after each X-ray burst, attributed to the increased
accretion rate. With these fares, we measure the speed of a neutron star compact jet
to be v c = 0.38−0.08
+0.11 , much slower than those from black holes at similar luminosities.
This discovery provides a powerful new tool in which we can determine the role that
individual system properties have on the jet speed, revealing the dominant jet
launching mechanism.
1) Global climate models that include sophisticated cloud schemes show that tidally locked planets can develop thick water clouds near the substellar point due to strong convection. These clouds greatly increase the planetary albedo and stabilize temperatures, allowing habitability at twice the stellar flux previously thought possible.
2) The cloud feedback is stabilizing, as higher stellar flux produces stronger convection and higher albedos. Substellar clouds can block outgoing radiation, reducing the day-night temperature contrast.
3) Non-tidally locked planets do not experience this stabilizing cloud feedback, as clouds only form over parts of the tropics and mid-latitudes. Their albedo decreases with increasing stellar flux, producing a destabil
Earth-like lithospheric thickness and heat flow on Venus consistent with acti...Sérgio Sacani
Venus is Earth’s twin in size and radiogenic heat budget, yet it remains
unclear how Venus loses its heat absent plate tectonics. Most Venusian
stagnant-lid models predict a thick lithosphere with heat fow about half
that of Earth’s mobile-lid regime. Here we estimate elastic lithospheric
thickness at 75 locations on Venus using topographic fexure at 65 coronae—
quasi-circular volcano-tectonic features—determined from Magellan
altimetry data. We fnd an average thickness at coronae of 11 ± 7 km. This
implies an average heat fow of 101 ± 88 mW m−2, higher than Earth’ s
average but similar to terrestrial values in actively extending areas. For
some locations, such as the Parga Chasma rift zone, we estimate heat fow
exceeding 75 mW m−2. Combined with a low-resolution map of global elastic
thickness, this suggests that coronae typically form on thin lithosphere,
instead of locally thinning the lithosphere via plume heating, and that most
regions of low elastic thickness are best explained by high heat fow rather
than crustal compensation. Our analysis identifes likely areas of active
extension and suggests that Venus has Earth-like lithospheric thickness
and global heat fow ranges. Together with the planet’s geologic history,
our fndings support a squishy-lid convective regime that relies on plumes,
intrusive magmatism and delamination to increase heat fow.
Melting curve of superionic ammonia at planetary interior conditionsSérgio Sacani
Under high pressures and temperatures, molecular systems with substantial
polarization charges, such as ammonia and water, are predicted to form
superionic phases and dense fluid states with dissociating molecules
and high electrical conductivity. This behaviour potentially plays a role
in explaining the origin of the multipolar magnetic fields of Uranus and
Neptune, whose mantles are thought to result from a mixture of H2O, NH3
and CH4 ices. Determining the stability domain, melting curve and electrical
conductivity of these superionic phases is therefore crucial for modelling
planetary interiors and dynamos. Here we report the melting curve of
superionic ammonia up to 300 GPa from laser-driven shock compression
of pre-compressed samples and atomistic calculations. We show that
ammonia melts at lower temperatures than water above 100 GPa and that
fluid ammonia’s electrical conductivity exceeds that of water at conditions
predicted by hot, super-adiabatic models for Uranus and Neptune, and
enhances the conductivity in their fluid water-rich dynamo layers.
This document summarizes simulations of graphene growth on a copper substrate. Monte Carlo simulations were performed on a honeycomb lattice with various levels of static and dynamic substrate disorder. For static disorder, carbon atoms reside on favorable substrate sites, reducing mobility and resulting in smaller islands. For dynamic disorder, the changing substrate allows islands to move and reform, enhancing island size at optimal temperatures. The substrate itself shows no ordering without carbon islands at high dynamic disorder temperatures.
The document presents evidence for azimuthal variations in cosmic ray ion acceleration at the blast wave of the supernova remnant SN 1006. Using radio, X-ray, and optical observations, the researchers find that the ratio of radii between the blast wave and contact discontinuity varies azimuthally, being smallest in the brightest synchrotron emission regions, indicating more efficient cosmic ray acceleration. They interpret this as evidence that the injection rate, magnetic field strength, and turbulence level - which influence cosmic ray acceleration - all vary azimuthally and are highest in the brightest regions.
This document discusses evidence that the Moon-forming impact occurred later than previously thought, at around 95 million years after the formation of the solar system. The study uses simulations of planetary formation to show a correlation between the timing of the last giant impact and the amount of mass later accreted by the planet. Comparing this to highly siderophile element abundances in Earth's mantle, which constrain the amount of late-accreted mass, the study determines the Moon-forming impact was most likely 95 million years after solar system formation. Earlier times of 40 million years or less are ruled out at a 99.9% confidence level. The simulations include both classical scenarios and scenarios where Jupiter and Saturn migrated inward early in the solar
We investigate a variety of short warning time, terminal mitigation scenarios via
fragmentation for a hypothetical impact of asteroid 2023 NT1, a Near-Earth Object (NEO) that
was discovered on July 15, 2023, two days after its closest approach to Earth on July 13. The
asteroid passed by Earth within ~0.25 lunar distances with a closest approach distance of ~105
km and speed of 11.27 km/s. Its size remains largely uncertain, with an estimated diameter range
of 26 – 58 m and probable diameter estimate (weighted by the NEO size frequency distribution)
of 34 m (JPL Sentry, September 12, 2023). The asteroid approached Earth from the direction of
the Sun, as did both the Chelyabinsk asteroid in 2013 and comet NEOWISE in 2021. As a result,
2023 NT1 remained undetected until after its closest approach. If it had been on a collision
course, it would have had an impact energy of ~1.5 Mt (assuming a spherical asteroid with the
probable diameter estimate of 34 m, 2.6 g/cm3 uniform density, and impact speed of 15.59 km/s).
2023 NT1 represents a threat that could have caused significant local damage (~3x Chelyabinsk
airburst energy). We utilize the PI (“Pulverize It”) method for planetary defense to model
potential mitigation scenarios of an object like 2023 NT1 through simulations of hypervelocity
asteroid disruption and atmospheric ground effects for the case of a terminal defense mode.
Simulations suggest that PI is an effective multimodal approach for planetary defense that can
operate in extremely short interdiction modes (with intercepts as short as hours prior to impact),
in addition to long interdiction time scales with months to years of warning. Our simulations
support the proposition that threats like 2023 NT1 can be effectively mitigated with intercepts of
one day (or less) prior to impact, yielding minimal to no ground damage, using modest resources
and existing technologies.
Web science emerged as a new interdisciplinary field to study and understand the World Wide Web. It aims to:
1) Model the Web's structure as a scale-free network and understand the architectural principles that fueled its growth.
2) Discover how online human interactions are driven by social conventions and how these interactions shape emergent properties like social networking and online communities.
3) Develop approaches to harness the Web's positive potential while addressing issues like privacy, security, and intellectual property through technical and policy solutions.
Major universities have established the Web Science Research Initiative to advance this new field through research collaborations, publications, and conferences. Important insights into search algorithms, network structure, and online behavior
This document discusses how geomagnetic storms can affect marine archaeological surveys by introducing noise and masking spatial variations in Earth's magnetic field that are used to identify archaeological anomalies. The study analyzed 34 geomagnetic storms and found that their sudden onset signatures were indistinguishable from archaeological anomalies. Based on this, it is estimated that 89.7-100% of strong geomagnetic storms will generate signatures that could be misinterpreted as archaeological sites. The document recommends improved data collection and processing methods to better account for geomagnetic storms and improve precision in identifying archaeological resources.
Detection of an atmosphere around the super earth 55 cancri eSérgio Sacani
We report the analysis of two new spectroscopic observations of the super-Earth 55 Cancri e, in the near
infrared, obtained with the WFC3 camera onboard the HST. 55 Cancri e orbits so close to its parent
star, that temperatures much higher than 2000 K are expected on its surface. Given the brightness
of 55 Cancri, the observations were obtained in scanning mode, adopting a very long scanning length
and a very high scanning speed. We use our specialized pipeline to take into account systematics
introduced by these observational parameters when coupled with the geometrical distortions of the
instrument. We measure the transit depth per wavelength channel with an average relative uncertainty
of 22 ppm per visit and nd modulations that depart from a straight line model with a 6 condence
level. These results suggest that 55 Cancri e is surrounded by an atmosphere, which is probably
hydrogen-rich. Our fully Bayesian spectral retrieval code, T -REx, has identied HCN to be the
most likely molecular candidate able to explain the features at 1.42 and 1.54 m. While additional
spectroscopic observations in a broader wavelength range in the infrared will be needed to conrm
the HCN detection, we discuss here the implications of such result. Our chemical model, developed
with combustion specialists, indicates that relatively high mixing ratios of HCN may be caused by a
high C/O ratio. This result suggests this super-Earth is a carbon-rich environment even more exotic
than previously thought.
- The document discusses two potential causes of the mass extinction event that wiped out the dinosaurs - massive volcanic activity from the Deccan Traps (in present-day India), and a large asteroid impact in what is now the Gulf of Mexico.
- Through climate and habitat modeling, the researchers found that scenarios involving prolonged global cooling from the asteroid impact led to a substantial reduction in suitable habitats for dinosaurs worldwide.
- In contrast, simulations of Deccan volcanism, even those with major global warming effects from carbon dioxide release, did not produce conditions severe enough to cause a dinosaur extinction.
- The asteroid impact may have been the primary driver of the non-avian dinosaur extinction, though volcanic warming likely reduced
THE IMPORTANCE OF MARTIAN ATMOSPHERE SAMPLE RETURN.Sérgio Sacani
The return of a sample of near-surface atmosphere from Mars would facilitate answers to several first-order science questions surrounding the formation and evolution of the planet. One of the important aspects of terrestrial planet formation in general is the role that primary atmospheres played in influencing the chemistry and structure of the planets and their antecedents. Studies of the martian atmosphere can be used to investigate the role of a primary atmosphere in its history. Atmosphere samples would also inform our understanding of the near-surface chemistry of the planet, and ultimately the prospects for life. High-precision isotopic analyses of constituent gases are needed to address these questions, requiring that the analyses are made on returned samples rather than in situ.
Filamentary structures as the origin of blazar jet radio variabilitySérgio Sacani
Supermassive black holes at the centre of active galactic nuclei power some
of the most luminous objects in the Universe. Typically, very-long-baseline
interferometric observations of blazars have revealed only funnel-like
morphologies with little information on the internal structure of the ejected
plasma or have lacked the dynamic range to reconstruct the extended jet
emission. Here we present microarcsecond-scale angular resolution images
of the blazar 3C 279 obtained at 22 GHz with the space very-long-baseline
interferometry mission RadioAstron, which allowed us to resolve the jet
transversely and reveal several flaments produced by plasma instabilities
in a kinetically dominated fow. The polarimetric properties derived
from our high-angular-resolution and broad-dynamic-range images are
consistent with the presence of a helical magnetic feld threaded to the jet.
We infer a clockwise rotation as seen in the direction of fow motion with an
intrinsic helix pitch angle of ~45° and a Lorentz factor of ~13 at the time of
observation. We also propose a model to explain blazar jet radio variability
in which emission features travelling down the jet may manifest as a result
of diferential Doppler boosting within the flaments, as opposed to the
standard shock-in-jet model. Characterizing such variability is particularly
important given the relevance of blazar physics from cosmic particle
acceleration to standard candles in cosmology.
Ähnlich wie Remote detection of a lunar granitic batholith at Compton–Belkovich (20)
The binding of cosmological structures by massless topological defectsSérgio Sacani
Assuming spherical symmetry and weak field, it is shown that if one solves the Poisson equation or the Einstein field
equations sourced by a topological defect, i.e. a singularity of a very specific form, the result is a localized gravitational
field capable of driving flat rotation (i.e. Keplerian circular orbits at a constant speed for all radii) of test masses on a thin
spherical shell without any underlying mass. Moreover, a large-scale structure which exploits this solution by assembling
concentrically a number of such topological defects can establish a flat stellar or galactic rotation curve, and can also deflect
light in the same manner as an equipotential (isothermal) sphere. Thus, the need for dark matter or modified gravity theory is
mitigated, at least in part.
EWOCS-I: The catalog of X-ray sources in Westerlund 1 from the Extended Weste...Sérgio Sacani
Context. With a mass exceeding several 104 M⊙ and a rich and dense population of massive stars, supermassive young star clusters
represent the most massive star-forming environment that is dominated by the feedback from massive stars and gravitational interactions
among stars.
Aims. In this paper we present the Extended Westerlund 1 and 2 Open Clusters Survey (EWOCS) project, which aims to investigate
the influence of the starburst environment on the formation of stars and planets, and on the evolution of both low and high mass stars.
The primary targets of this project are Westerlund 1 and 2, the closest supermassive star clusters to the Sun.
Methods. The project is based primarily on recent observations conducted with the Chandra and JWST observatories. Specifically,
the Chandra survey of Westerlund 1 consists of 36 new ACIS-I observations, nearly co-pointed, for a total exposure time of 1 Msec.
Additionally, we included 8 archival Chandra/ACIS-S observations. This paper presents the resulting catalog of X-ray sources within
and around Westerlund 1. Sources were detected by combining various existing methods, and photon extraction and source validation
were carried out using the ACIS-Extract software.
Results. The EWOCS X-ray catalog comprises 5963 validated sources out of the 9420 initially provided to ACIS-Extract, reaching a
photon flux threshold of approximately 2 × 10−8 photons cm−2
s
−1
. The X-ray sources exhibit a highly concentrated spatial distribution,
with 1075 sources located within the central 1 arcmin. We have successfully detected X-ray emissions from 126 out of the 166 known
massive stars of the cluster, and we have collected over 71 000 photons from the magnetar CXO J164710.20-455217.
The debris of the ‘last major merger’ is dynamically youngSérgio Sacani
The Milky Way’s (MW) inner stellar halo contains an [Fe/H]-rich component with highly eccentric orbits, often referred to as the
‘last major merger.’ Hypotheses for the origin of this component include Gaia-Sausage/Enceladus (GSE), where the progenitor
collided with the MW proto-disc 8–11 Gyr ago, and the Virgo Radial Merger (VRM), where the progenitor collided with the
MW disc within the last 3 Gyr. These two scenarios make different predictions about observable structure in local phase space,
because the morphology of debris depends on how long it has had to phase mix. The recently identified phase-space folds in Gaia
DR3 have positive caustic velocities, making them fundamentally different than the phase-mixed chevrons found in simulations
at late times. Roughly 20 per cent of the stars in the prograde local stellar halo are associated with the observed caustics. Based
on a simple phase-mixing model, the observed number of caustics are consistent with a merger that occurred 1–2 Gyr ago.
We also compare the observed phase-space distribution to FIRE-2 Latte simulations of GSE-like mergers, using a quantitative
measurement of phase mixing (2D causticality). The observed local phase-space distribution best matches the simulated data
1–2 Gyr after collision, and certainly not later than 3 Gyr. This is further evidence that the progenitor of the ‘last major merger’
did not collide with the MW proto-disc at early times, as is thought for the GSE, but instead collided with the MW disc within
the last few Gyr, consistent with the body of work surrounding the VRM.
Observation of Io’s Resurfacing via Plume Deposition Using Ground-based Adapt...Sérgio Sacani
Since volcanic activity was first discovered on Io from Voyager images in 1979, changes
on Io’s surface have been monitored from both spacecraft and ground-based telescopes.
Here, we present the highest spatial resolution images of Io ever obtained from a groundbased telescope. These images, acquired by the SHARK-VIS instrument on the Large
Binocular Telescope, show evidence of a major resurfacing event on Io’s trailing hemisphere. When compared to the most recent spacecraft images, the SHARK-VIS images
show that a plume deposit from a powerful eruption at Pillan Patera has covered part
of the long-lived Pele plume deposit. Although this type of resurfacing event may be common on Io, few have been detected due to the rarity of spacecraft visits and the previously low spatial resolution available from Earth-based telescopes. The SHARK-VIS instrument ushers in a new era of high resolution imaging of Io’s surface using adaptive
optics at visible wavelengths.
Earliest Galaxies in the JADES Origins Field: Luminosity Function and Cosmic ...Sérgio Sacani
We characterize the earliest galaxy population in the JADES Origins Field (JOF), the deepest
imaging field observed with JWST. We make use of the ancillary Hubble optical images (5 filters
spanning 0.4−0.9µm) and novel JWST images with 14 filters spanning 0.8−5µm, including 7 mediumband filters, and reaching total exposure times of up to 46 hours per filter. We combine all our data
at > 2.3µm to construct an ultradeep image, reaching as deep as ≈ 31.4 AB mag in the stack and
30.3-31.0 AB mag (5σ, r = 0.1” circular aperture) in individual filters. We measure photometric
redshifts and use robust selection criteria to identify a sample of eight galaxy candidates at redshifts
z = 11.5 − 15. These objects show compact half-light radii of R1/2 ∼ 50 − 200pc, stellar masses of
M⋆ ∼ 107−108M⊙, and star-formation rates of SFR ∼ 0.1−1 M⊙ yr−1
. Our search finds no candidates
at 15 < z < 20, placing upper limits at these redshifts. We develop a forward modeling approach to
infer the properties of the evolving luminosity function without binning in redshift or luminosity that
marginalizes over the photometric redshift uncertainty of our candidate galaxies and incorporates the
impact of non-detections. We find a z = 12 luminosity function in good agreement with prior results,
and that the luminosity function normalization and UV luminosity density decline by a factor of ∼ 2.5
from z = 12 to z = 14. We discuss the possible implications of our results in the context of theoretical
models for evolution of the dark matter halo mass function.
Multi-source connectivity as the driver of solar wind variability in the heli...Sérgio Sacani
The ambient solar wind that flls the heliosphere originates from multiple
sources in the solar corona and is highly structured. It is often described
as high-speed, relatively homogeneous, plasma streams from coronal
holes and slow-speed, highly variable, streams whose source regions are
under debate. A key goal of ESA/NASA’s Solar Orbiter mission is to identify
solar wind sources and understand what drives the complexity seen in the
heliosphere. By combining magnetic feld modelling and spectroscopic
techniques with high-resolution observations and measurements, we show
that the solar wind variability detected in situ by Solar Orbiter in March
2022 is driven by spatio-temporal changes in the magnetic connectivity to
multiple sources in the solar atmosphere. The magnetic feld footpoints
connected to the spacecraft moved from the boundaries of a coronal hole
to one active region (12961) and then across to another region (12957). This
is refected in the in situ measurements, which show the transition from fast
to highly Alfvénic then to slow solar wind that is disrupted by the arrival of
a coronal mass ejection. Our results describe solar wind variability at 0.5 au
but are applicable to near-Earth observatories.
Gliese 12 b: A Temperate Earth-sized Planet at 12 pc Ideal for Atmospheric Tr...Sérgio Sacani
Recent discoveries of Earth-sized planets transiting nearby M dwarfs have made it possible to characterize the
atmospheres of terrestrial planets via follow-up spectroscopic observations. However, the number of such planets
receiving low insolation is still small, limiting our ability to understand the diversity of the atmospheric
composition and climates of temperate terrestrial planets. We report the discovery of an Earth-sized planet
transiting the nearby (12 pc) inactive M3.0 dwarf Gliese 12 (TOI-6251) with an orbital period (Porb) of 12.76 days.
The planet, Gliese 12 b, was initially identified as a candidate with an ambiguous Porb from TESS data. We
confirmed the transit signal and Porb using ground-based photometry with MuSCAT2 and MuSCAT3, and
validated the planetary nature of the signal using high-resolution images from Gemini/NIRI and Keck/NIRC2 as
well as radial velocity (RV) measurements from the InfraRed Doppler instrument on the Subaru 8.2 m telescope
and from CARMENES on the CAHA 3.5 m telescope. X-ray observations with XMM-Newton showed the host
star is inactive, with an X-ray-to-bolometric luminosity ratio of log 5.7 L L X bol » - . Joint analysis of the light
curves and RV measurements revealed that Gliese 12 b has a radius of 0.96 ± 0.05 R⊕,a3σ mass upper limit of
3.9 M⊕, and an equilibrium temperature of 315 ± 6 K assuming zero albedo. The transmission spectroscopy metric
(TSM) value of Gliese 12 b is close to the TSM values of the TRAPPIST-1 planets, adding Gliese 12 b to the small
list of potentially terrestrial, temperate planets amenable to atmospheric characterization with JWST.
Gliese 12 b, a temperate Earth-sized planet at 12 parsecs discovered with TES...Sérgio Sacani
We report on the discovery of Gliese 12 b, the nearest transiting temperate, Earth-sized planet found to date. Gliese 12 is a
bright (V = 12.6 mag, K = 7.8 mag) metal-poor M4V star only 12.162 ± 0.005 pc away from the Solar system with one of the
lowest stellar activity levels known for M-dwarfs. A planet candidate was detected by TESS based on only 3 transits in sectors
42, 43, and 57, with an ambiguity in the orbital period due to observational gaps. We performed follow-up transit observations
with CHEOPS and ground-based photometry with MINERVA-Australis, SPECULOOS, and Purple Mountain Observatory,
as well as further TESS observations in sector 70. We statistically validate Gliese 12 b as a planet with an orbital period of
12.76144 ± 0.00006 d and a radius of 1.0 ± 0.1 R⊕, resulting in an equilibrium temperature of ∼315 K. Gliese 12 b has excellent
future prospects for precise mass measurement, which may inform how planetary internal structure is affected by the stellar
compositional environment. Gliese 12 b also represents one of the best targets to study whether Earth-like planets orbiting cool
stars can retain their atmospheres, a crucial step to advance our understanding of habitability on Earth and across the galaxy.
The importance of continents, oceans and plate tectonics for the evolution of...Sérgio Sacani
Within the uncertainties of involved astronomical and biological parameters, the Drake Equation
typically predicts that there should be many exoplanets in our galaxy hosting active, communicative
civilizations (ACCs). These optimistic calculations are however not supported by evidence, which is
often referred to as the Fermi Paradox. Here, we elaborate on this long-standing enigma by showing
the importance of planetary tectonic style for biological evolution. We summarize growing evidence
that a prolonged transition from Mesoproterozoic active single lid tectonics (1.6 to 1.0 Ga) to modern
plate tectonics occurred in the Neoproterozoic Era (1.0 to 0.541 Ga), which dramatically accelerated
emergence and evolution of complex species. We further suggest that both continents and oceans
are required for ACCs because early evolution of simple life must happen in water but late evolution
of advanced life capable of creating technology must happen on land. We resolve the Fermi Paradox
(1) by adding two additional terms to the Drake Equation: foc
(the fraction of habitable exoplanets
with significant continents and oceans) and fpt
(the fraction of habitable exoplanets with significant
continents and oceans that have had plate tectonics operating for at least 0.5 Ga); and (2) by
demonstrating that the product of foc
and fpt
is very small (< 0.00003–0.002). We propose that the lack
of evidence for ACCs reflects the scarcity of long-lived plate tectonics and/or continents and oceans on
exoplanets with primitive life.
A Giant Impact Origin for the First Subduction on EarthSérgio Sacani
Hadean zircons provide a potential record of Earth's earliest subduction 4.3 billion years ago. Itremains enigmatic how subduction could be initiated so soon after the presumably Moon‐forming giant impact(MGI). Earlier studies found an increase in Earth's core‐mantle boundary (CMB) temperature due to theaccumulation of the impactor's core, and our recent work shows Earth's lower mantle remains largely solid, withsome of the impactor's mantle potentially surviving as the large low‐shear velocity provinces (LLSVPs). Here,we show that a hot post‐impact CMB drives the initiation of strong mantle plumes that can induce subductioninitiation ∼200 Myr after the MGI. 2D and 3D thermomechanical computations show that a high CMBtemperature is the primary factor triggering early subduction, with enrichment of heat‐producing elements inLLSVPs as another potential factor. The models link the earliest subduction to the MGI with implications forunderstanding the diverse tectonic regimes of rocky planets.
Climate extremes likely to drive land mammal extinction during next supercont...Sérgio Sacani
Mammals have dominated Earth for approximately 55 Myr thanks to their
adaptations and resilience to warming and cooling during the Cenozoic. All
life will eventually perish in a runaway greenhouse once absorbed solar
radiation exceeds the emission of thermal radiation in several billions of
years. However, conditions rendering the Earth naturally inhospitable to
mammals may develop sooner because of long-term processes linked to
plate tectonics (short-term perturbations are not considered here). In
~250 Myr, all continents will converge to form Earth’s next supercontinent,
Pangea Ultima. A natural consequence of the creation and decay of Pangea
Ultima will be extremes in pCO2 due to changes in volcanic rifting and
outgassing. Here we show that increased pCO2, solar energy (F⨀;
approximately +2.5% W m−2 greater than today) and continentality (larger
range in temperatures away from the ocean) lead to increasing warming
hostile to mammalian life. We assess their impact on mammalian
physiological limits (dry bulb, wet bulb and Humidex heat stress indicators)
as well as a planetary habitability index. Given mammals’ continued survival,
predicted background pCO2 levels of 410–816 ppm combined with increased
F⨀ will probably lead to a climate tipping point and their mass extinction.
The results also highlight how global landmass configuration, pCO2 and F⨀
play a critical role in planetary habitability.
Constraints on Neutrino Natal Kicks from Black-Hole Binary VFTS 243Sérgio Sacani
The recently reported observation of VFTS 243 is the first example of a massive black-hole binary
system with negligible binary interaction following black-hole formation. The black-hole mass (≈10M⊙)
and near-circular orbit (e ≈ 0.02) of VFTS 243 suggest that the progenitor star experienced complete
collapse, with energy-momentum being lost predominantly through neutrinos. VFTS 243 enables us to
constrain the natal kick and neutrino-emission asymmetry during black-hole formation. At 68% confidence
level, the natal kick velocity (mass decrement) is ≲10 km=s (≲1.0M⊙), with a full probability distribution
that peaks when ≈0.3M⊙ were ejected, presumably in neutrinos, and the black hole experienced a natal
kick of 4 km=s. The neutrino-emission asymmetry is ≲4%, with best fit values of ∼0–0.2%. Such a small
neutrino natal kick accompanying black-hole formation is in agreement with theoretical predictions.
Detectability of Solar Panels as a TechnosignatureSérgio Sacani
In this work, we assess the potential detectability of solar panels made of silicon on an Earth-like
exoplanet as a potential technosignature. Silicon-based photovoltaic cells have high reflectance in the
UV-VIS and in the near-IR, within the wavelength range of a space-based flagship mission concept
like the Habitable Worlds Observatory (HWO). Assuming that only solar energy is used to provide
the 2022 human energy needs with a land cover of ∼ 2.4%, and projecting the future energy demand
assuming various growth-rate scenarios, we assess the detectability with an 8 m HWO-like telescope.
Assuming the most favorable viewing orientation, and focusing on the strong absorption edge in the
ultraviolet-to-visible (0.34 − 0.52 µm), we find that several 100s of hours of observation time is needed
to reach a SNR of 5 for an Earth-like planet around a Sun-like star at 10pc, even with a solar panel
coverage of ∼ 23% land coverage of a future Earth. We discuss the necessity of concepts like Kardeshev
Type I/II civilizations and Dyson spheres, which would aim to harness vast amounts of energy. Even
with much larger populations than today, the total energy use of human civilization would be orders of
magnitude below the threshold for causing direct thermal heating or reaching the scale of a Kardashev
Type I civilization. Any extraterrrestrial civilization that likewise achieves sustainable population
levels may also find a limit on its need to expand, which suggests that a galaxy-spanning civilization
as imagined in the Fermi paradox may not exist.
Jet reorientation in central galaxies of clusters and groups: insights from V...Sérgio Sacani
Recent observations of galaxy clusters and groups with misalignments between their central AGN jets
and X-ray cavities, or with multiple misaligned cavities, have raised concerns about the jet – bubble
connection in cooling cores, and the processes responsible for jet realignment. To investigate the
frequency and causes of such misalignments, we construct a sample of 16 cool core galaxy clusters and
groups. Using VLBA radio data we measure the parsec-scale position angle of the jets, and compare
it with the position angle of the X-ray cavities detected in Chandra data. Using the overall sample
and selected subsets, we consistently find that there is a 30% – 38% chance to find a misalignment
larger than ∆Ψ = 45◦ when observing a cluster/group with a detected jet and at least one cavity. We
determine that projection may account for an apparently large ∆Ψ only in a fraction of objects (∼35%),
and given that gas dynamical disturbances (as sloshing) are found in both aligned and misaligned
systems, we exclude environmental perturbation as the main driver of cavity – jet misalignment.
Moreover, we find that large misalignments (up to ∼ 90◦
) are favored over smaller ones (45◦ ≤ ∆Ψ ≤
70◦
), and that the change in jet direction can occur on timescales between one and a few tens of Myr.
We conclude that misalignments are more likely related to actual reorientation of the jet axis, and we
discuss several engine-based mechanisms that may cause these dramatic changes.
Extensive Pollution of Uranus and Neptune’s Atmospheres by Upsweep of Icy Mat...Sérgio Sacani
In the Nice model of solar system formation, Uranus and Neptune undergo an orbital upheaval,
sweeping through a planetesimal disk. The region of the disk from which material is accreted by
the ice giants during this phase of their evolution has not previously been identified. We perform
direct N-body orbital simulations of the four giant planets to determine the amount and origin of solid
accretion during this orbital upheaval. We find that the ice giants undergo an extreme bombardment
event, with collision rates as much as ∼3 per hour assuming km-sized planetesimals, increasing the
total planet mass by up to ∼0.35%. In all cases, the initially outermost ice giant experiences the
largest total enhancement. We determine that for some plausible planetesimal properties, the resulting
atmospheric enrichment could potentially produce sufficient latent heat to alter the planetary cooling
timescale according to existing models. Our findings suggest that substantial accretion during this
phase of planetary evolution may have been sufficient to impact the atmospheric composition and
thermal evolution of the ice giants, motivating future work on the fate of deposited solid material.
Exomoons & Exorings with the Habitable Worlds Observatory I: On the Detection...Sérgio Sacani
The highest priority recommendation of the Astro2020 Decadal Survey for space-based astronomy
was the construction of an observatory capable of characterizing habitable worlds. In this paper series
we explore the detectability of and interference from exomoons and exorings serendipitously observed
with the proposed Habitable Worlds Observatory (HWO) as it seeks to characterize exoplanets, starting
in this manuscript with Earth-Moon analog mutual events. Unlike transits, which only occur in systems
viewed near edge-on, shadow (i.e., solar eclipse) and lunar eclipse mutual events occur in almost every
star-planet-moon system. The cadence of these events can vary widely from ∼yearly to multiple events
per day, as was the case in our younger Earth-Moon system. Leveraging previous space-based (EPOXI)
lightcurves of a Moon transit and performance predictions from the LUVOIR-B concept, we derive
the detectability of Moon analogs with HWO. We determine that Earth-Moon analogs are detectable
with observation of ∼2-20 mutual events for systems within 10 pc, and larger moons should remain
detectable out to 20 pc. We explore the extent to which exomoon mutual events can mimic planet
features and weather. We find that HWO wavelength coverage in the near-IR, specifically in the 1.4 µm
water band where large moons can outshine their host planet, will aid in differentiating exomoon signals
from exoplanet variability. Finally, we predict that exomoons formed through collision processes akin
to our Moon are more likely to be detected in younger systems, where shorter orbital periods and
favorable geometry enhance the probability and frequency of mutual events.
Emergent ribozyme behaviors in oxychlorine brines indicate a unique niche for...Sérgio Sacani
Mars is a particularly attractive candidate among known astronomical objects
to potentially host life. Results from space exploration missions have provided
insights into Martian geochemistry that indicate oxychlorine species, particularly perchlorate, are ubiquitous features of the Martian geochemical landscape. Perchlorate presents potential obstacles for known forms of life due to
its toxicity. However, it can also provide potential benefits, such as producing
brines by deliquescence, like those thought to exist on present-day Mars. Here
we show perchlorate brines support folding and catalysis of functional RNAs,
while inactivating representative protein enzymes. Additionally, we show
perchlorate and other oxychlorine species enable ribozyme functions,
including homeostasis-like regulatory behavior and ribozyme-catalyzed
chlorination of organic molecules. We suggest nucleic acids are uniquely wellsuited to hypersaline Martian environments. Furthermore, Martian near- or
subsurface oxychlorine brines, and brines found in potential lifeforms, could
provide a unique niche for biomolecular evolution.
Continuum emission from within the plunging region of black hole discsSérgio Sacani
The thermal continuum emission observed from accreting black holes across X-ray bands has the potential to be leveraged as a
powerful probe of the mass and spin of the central black hole. The vast majority of existing ‘continuum fitting’ models neglect
emission sourced at and within the innermost stable circular orbit (ISCO) of the black hole. Numerical simulations, however,
find non-zero emission sourced from these regions. In this work, we extend existing techniques by including the emission
sourced from within the plunging region, utilizing new analytical models that reproduce the properties of numerical accretion
simulations. We show that in general the neglected intra-ISCO emission produces a hot-and-small quasi-blackbody component,
but can also produce a weak power-law tail for more extreme parameter regions. A similar hot-and-small blackbody component
has been added in by hand in an ad hoc manner to previous analyses of X-ray binary spectra. We show that the X-ray spectrum
of MAXI J1820+070 in a soft-state outburst is extremely well described by a full Kerr black hole disc, while conventional
models that neglect intra-ISCO emission are unable to reproduce the data. We believe this represents the first robust detection of
intra-ISCO emission in the literature, and allows additional constraints to be placed on the MAXI J1820 + 070 black hole spin
which must be low a• < 0.5 to allow a detectable intra-ISCO region. Emission from within the ISCO is the dominant emission
component in the MAXI J1820 + 070 spectrum between 6 and 10 keV, highlighting the necessity of including this region. Our
continuum fitting model is made publicly available.
WASP-69b’s Escaping Envelope Is Confined to a Tail Extending at Least 7 RpSérgio Sacani
Studying the escaping atmospheres of highly irradiated exoplanets is critical for understanding the physical
mechanisms that shape the demographics of close-in planets. A number of planetary outflows have been observed
as excess H/He absorption during/after transit. Such an outflow has been observed for WASP-69b by multiple
groups that disagree on the geometry and velocity structure of the outflow. Here, we report the detection of this
planet’s outflow using Keck/NIRSPEC for the first time. We observed the outflow 1.28 hr after egress until the
target set, demonstrating the outflow extends at least 5.8 × 105 km or 7.5 Rp This detection is significantly longer
than previous observations, which report an outflow extending ∼2.2 planet radii just 1 yr prior. The outflow is
blueshifted by −23 km s−1 in the planetary rest frame. We estimate a current mass-loss rate of 1 M⊕ Gyr−1
. Our
observations are most consistent with an outflow that is strongly sculpted by ram pressure from the stellar wind.
However, potential variability in the outflow could be due to time-varying interactions with the stellar wind or
differences in instrumental precision.
PPT on Direct Seeded Rice presented at the three-day 'Training and Validation Workshop on Modules of Climate Smart Agriculture (CSA) Technologies in South Asia' workshop on April 22, 2024.
(June 12, 2024) Webinar: Development of PET theranostics targeting the molecu...Scintica Instrumentation
Targeting Hsp90 and its pathogen Orthologs with Tethered Inhibitors as a Diagnostic and Therapeutic Strategy for cancer and infectious diseases with Dr. Timothy Haystead.
Immersive Learning That Works: Research Grounding and Paths ForwardLeonel Morgado
We will metaverse into the essence of immersive learning, into its three dimensions and conceptual models. This approach encompasses elements from teaching methodologies to social involvement, through organizational concerns and technologies. Challenging the perception of learning as knowledge transfer, we introduce a 'Uses, Practices & Strategies' model operationalized by the 'Immersive Learning Brain' and ‘Immersion Cube’ frameworks. This approach offers a comprehensive guide through the intricacies of immersive educational experiences and spotlighting research frontiers, along the immersion dimensions of system, narrative, and agency. Our discourse extends to stakeholders beyond the academic sphere, addressing the interests of technologists, instructional designers, and policymakers. We span various contexts, from formal education to organizational transformation to the new horizon of an AI-pervasive society. This keynote aims to unite the iLRN community in a collaborative journey towards a future where immersive learning research and practice coalesce, paving the way for innovative educational research and practice landscapes.
Mending Clothing to Support Sustainable Fashion_CIMaR 2024.pdfSelcen Ozturkcan
Ozturkcan, S., Berndt, A., & Angelakis, A. (2024). Mending clothing to support sustainable fashion. Presented at the 31st Annual Conference by the Consortium for International Marketing Research (CIMaR), 10-13 Jun 2024, University of Gävle, Sweden.
ESA/ACT Science Coffee: Diego Blas - Gravitational wave detection with orbita...Advanced-Concepts-Team
Presentation in the Science Coffee of the Advanced Concepts Team of the European Space Agency on the 07.06.2024.
Speaker: Diego Blas (IFAE/ICREA)
Title: Gravitational wave detection with orbital motion of Moon and artificial
Abstract:
In this talk I will describe some recent ideas to find gravitational waves from supermassive black holes or of primordial origin by studying their secular effect on the orbital motion of the Moon or satellites that are laser ranged.
Authoring a personal GPT for your research and practice: How we created the Q...Leonel Morgado
Thematic analysis in qualitative research is a time-consuming and systematic task, typically done using teams. Team members must ground their activities on common understandings of the major concepts underlying the thematic analysis, and define criteria for its development. However, conceptual misunderstandings, equivocations, and lack of adherence to criteria are challenges to the quality and speed of this process. Given the distributed and uncertain nature of this process, we wondered if the tasks in thematic analysis could be supported by readily available artificial intelligence chatbots. Our early efforts point to potential benefits: not just saving time in the coding process but better adherence to criteria and grounding, by increasing triangulation between humans and artificial intelligence. This tutorial will provide a description and demonstration of the process we followed, as two academic researchers, to develop a custom ChatGPT to assist with qualitative coding in the thematic data analysis process of immersive learning accounts in a survey of the academic literature: QUAL-E Immersive Learning Thematic Analysis Helper. In the hands-on time, participants will try out QUAL-E and develop their ideas for their own qualitative coding ChatGPT. Participants that have the paid ChatGPT Plus subscription can create a draft of their assistants. The organizers will provide course materials and slide deck that participants will be able to utilize to continue development of their custom GPT. The paid subscription to ChatGPT Plus is not required to participate in this workshop, just for trying out personal GPTs during it.
Describing and Interpreting an Immersive Learning Case with the Immersion Cub...Leonel Morgado
Current descriptions of immersive learning cases are often difficult or impossible to compare. This is due to a myriad of different options on what details to include, which aspects are relevant, and on the descriptive approaches employed. Also, these aspects often combine very specific details with more general guidelines or indicate intents and rationales without clarifying their implementation. In this paper we provide a method to describe immersive learning cases that is structured to enable comparisons, yet flexible enough to allow researchers and practitioners to decide which aspects to include. This method leverages a taxonomy that classifies educational aspects at three levels (uses, practices, and strategies) and then utilizes two frameworks, the Immersive Learning Brain and the Immersion Cube, to enable a structured description and interpretation of immersive learning cases. The method is then demonstrated on a published immersive learning case on training for wind turbine maintenance using virtual reality. Applying the method results in a structured artifact, the Immersive Learning Case Sheet, that tags the case with its proximal uses, practices, and strategies, and refines the free text case description to ensure that matching details are included. This contribution is thus a case description method in support of future comparative research of immersive learning cases. We then discuss how the resulting description and interpretation can be leveraged to change immersion learning cases, by enriching them (considering low-effort changes or additions) or innovating (exploring more challenging avenues of transformation). The method holds significant promise to support better-grounded research in immersive learning.
20240520 Planning a Circuit Simulator in JavaScript.pptx
Remote detection of a lunar granitic batholith at Compton–Belkovich
1. 116 | Nature | Vol 620 | 3 August 2023
Article
Remotedetectionofalunargranitic
batholithatCompton–Belkovich
Matthew A. Siegler1,2,7✉, Jianqing Feng1,2,7✉, Katelyn Lehman-Franco2
,
Jeffery C. Andrews-Hanna3
, Rita C. Economos2
, Michael St. Clair4
, Chase Million4
,
James W. Head5
, Timothy D. Glotch6
& Mackenzie N. White2
GranitesarenearlyabsentintheSolarSystemoutsideofEarth.Achievinggranitic
compositionsinmagmaticsystemsrequiresmulti-stagemeltingandfractionation,
whichalsoincreasestheconcentrationofradiogenicelements1
.Abundantwaterand
platetectonicsfacilitatetheseprocessesonEarth,aidinginremelting.Althoughthese
driversareabsentontheMoon,smallgranitesampleshavebeenfound,butdetails
oftheiroriginandthescaleofsystemstheyrepresentareunknown2
.Herewereport
microwave-wavelengthmeasurementsofananomalouslyhotgeothermalsourcethat
isbestexplainedbythepresenceofanapproximately50-kilometre-diametergranitic
systembelowthethorium-richfarsidefeatureknownasCompton–Belkovich.Passive
microwaveradiometryissensitivetotheintegratedthermalgradienttoseveral
wavelengthsdepth.The3–37-gigahertzantennatemperaturesoftheChang’e-1and
Chang’e-2microwaveinstrumentsallowustomeasureapeakheatfluxofabout
180 milliwattspersquaremetre,whichisabout20timeshigherthanthatofthe
averagelunarhighlands3,4
.Thesurprisingmagnitudeandgeographicextentofthis
featureimplyanEarth-like,evolvedgraniticsystemlargerthanbelievedpossibleon
theMoon,especiallyoutsideoftheProcellarumregion5
.Furthermore,thesemethods
aregeneralizable:similarusesofpassiveradiometricdatacouldvastlyexpandour
knowledgeofgeothermalprocessesontheMoonandotherplanetarybodies.
Granitic rocks are common on Earth owing in part to the presence of
abundantwaterandplatetectonics,whichaidinmeltingandrecycling
crustal materials. Igneous systems elsewhere in the Solar System are
dominatedbybasalt,representingsingle-stagemeltingofmantlerock.
Graniteproductionrequiresmulti-stageremeltingofbasaltorcrystal
fractionationofbasalticliquids.Theseprocessesalsodriveanincreased
concentrationofincompatibleelementssuchassiliconandradiogenic
potassium, thorium (Th) and uranium (U)1
. Rare granitic clasts found
in lunar samples contain a high radiogenic concentration2
. However,
the origin and scale of the systems that produced them are unknown.
Lunarsilicicvolcanicmaterials,foundprimarilyinthenearsideProcel-
larum region5
, are generally coincident with high Th concentrations
detectedwithorbitalgamma-raydata6–9
.Still,thereislittletoconstrain
the subsurface structures and processes that created these systems.
An enigmatic farside feature known as Compton–Belkovich6,9
has
the highest localized Th concentrations on the Moon. Located at
61.2° N,99.7° Ebetweenitstwonamesakecraters,thecentralregionof
Compton–Belkovich has been mapped as a likely volcanic feature
andisoftenreferredtoastheCompton–BelkovichVolcanicComplex
(CBVC)10–15
.Herewepresentthediscoverythatalargegraniticbatholith,
similarinvolumetoterrestrialbatholithssuchastheAndeanAltiplano–
Puna Magma Body16
underlays Compton–Belkovich. We identify this
CBVCbatholiththroughabroad,increasedlocalgeothermalheatflux,
which peaks at about 180 mW m−2
—approximately 20 times that of
the background lunar highlands15
and over 8 times that measured at
the Apollo 15 site16
. Such a high heat flux requires a large mid-crustal
bodywithhigherradiogenicelementconcentrationsthanpreviously
interpreted from orbital observations4,7
. Here we detail evidence
based on a combination of models and data from the Chang’e-1
(CE-1) and Chang’e-2 (CE-2) orbiters, NASA’s Lunar Reconnaissance
Orbiter (LRO), and past data from the Lunar Prospector, the Gravity
RecoveryandInteriorLaboratory(GRAIL),Chandrayaan-1andApollo
missions.
The CE-1 and CE-2 orbiters carried four-channel (3–37 GHz) micro-
waveradiometer(MRM)instruments.Thesedataprovidenear-global
coverage over most of the diurnal cycle, including 8 CE-1 and 13 CE-2
passes over the CBVC. The maps presented here are generally from
CE-2, which had a lower orbit and therefore higher spatial resolution.
MRMdataareatantennatemperature(TA),whichresultsfromemitted
brightness temperatures (Tb) as seen by the instrument field of view.
Figure1showsthe3-GHzmidnightTAintheCBVCregion(afterlatitu-
dinaltrendshavebeenremovedandnormalizedto61° N),revealingan
enhancement of about 9 K, coincident with the Th anomaly. A similar
‘hotspot’ is observed at all frequencies, at all local times, in both CE-1
andCE-2microwavedata(Methods).WefindthatthisTbanomalycan
only be explained by an enhanced geothermal gradient, which also
https://doi.org/10.1038/s41586-023-06183-5
Received: 7 September 2022
Accepted: 9 May 2023
Published online: 5 July 2023
Check for updates
1
Planetary Science Institute, Tucson, AZ, USA. 2
Department of Earth Sciences, Southern Methodist University, Dallas, TX, USA. 3
Department of Planetary Sciences/Lunar and Planetary
Laboratory, University of Arizona, Tucson, AZ, USA. 4
Million Concepts, Louisville, KY, USA. 5
Department of Earth, Environmental and Planetary Sciences, Brown University, Providence, RI, USA.
6
Department of Geosciences, SUNY Stony Brook, Stony Brook, NY, USA. 7
These authors contributed equally: Matthew A. Siegler, Jianqing Feng. ✉e-mail: msiegler@psi.edu; jfeng@psi.edu
2. Nature | Vol 620 | 3 August 2023 | 117
provides a technique that could provide a window into the interior
compositions of the Moon and other planetary bodies.
The CBVC consists of a central, aproximately 15-km-diameter plain
ringed by 3-km-scale domes8–12
. The high-albedo interior shows a
short-wavelengthinfraredChristiansenfeatureconsistentwithasilicic
surface8
,andphotometricdetectionsofmineralsandesiteanddacite11
,
whichisproposedevidenceoferuptedrhyoliticlavas8–12
.Interiortothe
domes, several groups have mapped what appear to be circumferen-
tial faulting suggestive of a piston-style collapsed caldera10,12
. These
features have been hypothesized to mark the edge of a once-inflated
magmabody,potentiallynowevacuated,approximately13 kmindiam-
eter.ThegreaterregionsurroundingtheCBVCshowsanenhancedTh
concentration,postulatedtobeanashfalldeposit9
,leadingtoestimates
oferuptedmaterials’volumeandplausiblewatercontent17
.However,
previousstudieshavebeenlimitedtostudyingthesurfacesignatureof
thevolcanism,makingindirectinferencesregardingwhatliesbeneath.
Microwave radiometry provides a means to peer below the surface
tomeasuretheintegratedsubsurfacephysicaltemperature.Themeas-
urementfrequencyandthedielectricproperties(summarizedbythe
losstangent,whichistheratiobetweentherealandimaginarydielec-
tric constants)18,19
controls the depth over which materials add to the
emitted radiance. Lower frequencies (longer wavelengths) and lower
loss tangents will sense heat from greater depths. Conversely, higher
frequencies and higher loss tangents will sense temperatures closer
to the surface. For MRM frequencies and lunar materials, sounding
depths are estimated at about 0.3 m to 5.6 m (ref. 19).
On Earth, water’s high dielectric loss limits microwave penetra-
tion.TheMoon,Marsandotherplanetarybodieswithdryconditions,
regolith cover and low atmospheric pressure exhibit extremely low
loss tangents (<0.01), enabling microwave remote sensing to greater
depths.Furthermore,thelowthermalconductivityofthelunarregolith
(<10−3
W m−1
K−1
) both shows diurnal temperature variations (to the
upperapproximately50 cm)andprovideshighgeothermalgradients
(>1 K m−1
)4
.Consequently,increasesintemperaturewithdepthowingto
thegeothermalgradientwillincreasemeasurablebrightnesstempera-
tures,withastrongersignalatlowerfrequencies.Figure2illustratesthe
relationshipbetweenthemodelledgradientfromvariousgeothermal
fluxes(Fig.2a),theweightingfunctionoverwhichemittedheatisinte-
gratedforeachChang’efrequency(Fig.2b)andtheresultingincrease
in relative brightness temperature as a function of heat flux (Fig. 2c).
We find no plausible explanation for the high TAs other than an
enhanced subsurface geothermal heat source. Low albedo can cause
higher Tb, but the CBVC has a higher albedo than its surroundings.
Changesinnear-surfacedensityorlosstangentwillalterthediurnalTb
amplitude19
,buthigherTbareseenatalllocaltimes.WefindtheCBVC
feature is similar in near-surface density and loss to the surrounding
region,withalosstangentofabout0.005–0.01(Methods).Withthese
losses, 3-GHz measurements should be sensitive to heat within the
upper approximately 5.5 m (ref. 19).
TheTAobtainedbyamicrowaveradiometerdependsontheinstru-
ment radiation pattern (the angular dependence of power density).
Usingamulti-frequencyfitattwoaltitudes(about200 kmforCE-1and
about100 kmforCE-2)andinstrumentantennapatterns(Methods),we
canusethevariableresolutiontocharacterizethemagnitude,sizeand
shapeoftheheatsource.First,wecreateaforwardmodelofsubsurface
emissionfromsolarheating,fittoLRODivinerinfraredmeasurements
accounting for effects of slope, azimuth, density, LRO Diviner rock
abundance and loss tangents fit from Chang’e data (Methods). Then
weapplyafrequency-dependentantennapatterntotheforwardmodel
of the emitted microwave radiance, converting from modelled Tb to
TA. The resulting TA models provide a good fit for temperature vari-
ations owing to topography and surface geology, but reveal a strong
Tb excess in both CE-1 and CE-2 data at the CBVC (Methods), seen at
all frequencies (Fig. 3).
Althoughthisenhancement’slocationcoincideswiththeincreased
surface Th observed at the CBVC7,9
, it is a much larger increase than
explainablebysurfacematerials.Previousorbitalmeasurementsesti-
mate CBVC to have up to about 26-ppm Th (ref. 9), within the range
80º E 88º E 96º E 104º E 112º E 120º E
65º N
65º N
63º N
63º N
61º N
59º N
57º N
Belkovich
Compton
Compton–Belkovich
10
9
8
7
6
5
4
3
2
3-GHz
ΔTA
(K)
West
Dome
East
Dome
North Dome
–10 –8 –6 2
0
–2
–4 6
4 8 10
3-GHz ΔTA, corrected for latitude (K)
b
a
c
Latitude
Longitude
Fig.1|Latitudinallycorrected3-GHzTAshownatmidnightlocaltime.
a,ThesedatashowaclearlocalizedTAenhancementofabout9 Kcentredon
themappedCompton–Belkovichtopographicfeature.Thisfeatureisnot
explainablebytopography,surfacerockdistributionormaterialproperties
andisseenatallfrequenciesandtimesofday(Methods).b,c,Thecontext
globeshowsLunarProspector-measuredTh,scaled0–35-ppmTh(b)andthe
perspectiveviewshowstheTAsuperimposedonthecentralCBVCcaldera
topography(c).
3. 118 | Nature | Vol 620 | 3 August 2023
Article
of lunar granitic samples18
. A heat flux of 180 mW m−2
would require
a layer of roughly 45 km of such material, neglecting any lateral heat
conduction, implying the material below the surface exceeds con-
centrations estimated at the surface. In reality, heat will spread into
the surrounding crust, so 26-ppm Th would require an even thicker
deposit, exceeding the approximately 50-km crustal column in this
location20
. This lateral spread of heat flux helps define the size and
depth of the heat source, as a wider or deeper source would increase
thespreadbytheconductionofheatthroughthecrust.Althoughthere
is a trade-off between the source depth, size and radiogenic element
concentration,wecanprovideboundsbyexaminingremotesensing,
samples and petrologic data. On the basis of returned igneous lunar
–100 –50 0 50 100
0
50
100
150
Lower pluton
Distance from centre (km)
200
Model
heat
flux
(mW
m
–2
)
Upper pluton
Combined heat
flux + 8 mW m–2
background
–100 –50 0 50 100
Distance from centre (km)
0
5
10
15
20
25
30
Model
brightness
temperature
(K)
3 GHz
7.8 GHz
19.35 GHz
37 GHz
–50 0 50
Distance from centre (km)
0
2
4
6
8
10
Model
antenna
temperature
(K)
3 GHz, CE-1
3 GHz, CE-2
7.8 GHz, CE-1
7.8 GHz, CE-2
19.35 GHz, CE-1
19.35 GHz, CE-2
37 GHz, CE-1
37 GHz, CE-2
0.05 0.10 0.15 0.20
Heat flux (W m–2)
0
5
10
15
20
25
30
Brightness
temperature
difference
(K)
3 GHz
7.8 GHz
19.35 GHz
37 GHz
Surface temperature
0 5 10 15
Weighting function (×10–3)
0
0.5
1.0
1.5
2.0
Depth
(m)
3 GHz
7.8 GHz
19.35 GHz
37 GHz
150 200 250 300
Temperature (K)
0
0.5
1.0
1.5
2.0
Depth
(m)
8 mW m−2
21 mW m−2
80 mW m−2
150 mW m−2
a b
f
e
d
c
Fig.2|Microwaveexpectationsfromageothermalsource.a,Physical
temperatureversusdepthfortheCBVClocationforvariousgeothermalfluxes.
b,TheCE-1andCE-2 MRMweightingfunctionsinhighlandsregolith.c,TheΔTb
foragivenheatflux.Thedashedlinesrepresent±10%variationinlosstangent.
d,Theheatfluxfromournominaltwo-plutonmodel(orange)resultingfrom
thecombinedupper(blue)andlower(red)plutoncontributionswith8 mW m−2
backgroundheatflux.e,TheresultingΔTbforeachmeasurementforourend-
membertwo-plutonmodel.f,TheresultingΔTAforeachmeasurementforour
end-membertwo-plutonmodel.
–150 –100 –50 0 50 100 150
–2
0
2
4
6
8
10
Antenna
temperature
(K)
3 GHz, CE-1
3 GHz, CE-2
CE-1 model
CE-2 model
–150 –100 –50 0 50 100 150
–4
–2
0
2
4
6
8
10
7.8 GHz, CE-1
7.8 GHz, CE-2
CE-1 model
CE-2 model
–150 –100 –50 0 50 100 150
Distance from centre (km)
–2
0
2
4
Antenna
temperature
(K)
19.35 GHz, CE-1
19.35 GHz, CE-2
CE-1 model
CE-2 model
–150 –100 –50 0 50 100 150
Distance from centre (km)
–4
–2
0
2
4
6
37 GHz, CE-1
37 GHz, CE-2
CE-1 model
CE-2 model
Antenna
temperature
(K)
Antenna
temperature
(K)
a
c
b
d
Distance from centre (km) Distance from centre (km)
Fig.3|DataminusforwardmodelTAcomparedwiththebest-fitpluton
model.a–d,The3-GHz(a),7.8-GHz(b),19.35-GHz(c)and37-GHz(d)CE-1and
CE-2residualΔTAdata-modelasafunctionofdistancefromthecentreofthe
CBVC.Negativeandpositivevaluesareaveragesinradialdistancefromthe
centreoftheCBVCwith1σerrorforalldatawestwardsandeastwardsofthe
feature,respectively.AclearspikeisseenatallfrequenciesasmappedinFig.1
andMethods.TheinputmodelheatfluxvaluesarefromFig.2d,andFig.2e,f
showshowtheseΔTAvaluesresultfromtheheatfluxinputs.
4. Nature | Vol 620 | 3 August 2023 | 119
samples, only quartz monzodiorite, felsite and granite samples have
higher than 26-ppm Th.
TheevidenceofTh-richsilicicvolcanismfromremotesensing,geo-
morphology, and Th-rich granites and quartz monzodiorites within
the Apollo samples lead to a reasonable assertion that the CBVC may
be underlain by a granitic body8,12–15
. Therefore, we attempt to fit the
residual TA increase with a forwards model of a discrete subsurface
geothermal heat source assuming a geometry of an elliptical pluton.
We give crustal material outside the CBVC commonly assumed heat
production values21
, resulting in a surface flux of about 8 mW m−2
. To
matchtheobservedTbandgeometry,webeginwitha13-km-wideellip-
soidal body at 1-km depth. To provide a peak heat flux of 180 mW m−2
on the surface would require about 60 × 10−6
W m−3
of heat produc-
tion. However, this is about 3 times the heat production of the most
radiogenic materials found in lunar samples22
, equivalent to about
400-ppm Th, which is highly unlikely. To examine reasonable source
materials,welooktohigh-ThApollolunarsamples:thesefallintothree
classes; 35–44-ppm Th quartz monzodiorites (here labelled GA)23,24
,
about 62–70-ppm Th granites (GB)22,23,25
and a single, highly evolved
Apollo 12 granite sample with 132-ppm Th (GC)25
.
Modelling the upper body as GC composition can serve as an
end-membercase,butitselfisprobablyunreasonablyhigh.Evenwith
this high radiogenic concentration, a 13-km body will not produce
enoughheat(itresultsintheblueheatfluxcurveinFig.2d).Therefore,
weconcludethattheCBVCunderlainbyadeeper,muchlargerandprob-
ably less radiogenic body. Such a large, second body is also a sensible
geologicassumptionasitwouldprovidealower-Th,intermediate-stage
reservoir from which to distil the upper pluton. In reality, the lower
body is probably composed of several intermediate chambers and
sills (Methods), with this ellipsoidal shape approximating their net
heat production and gravity.
Withthissimplifiedgeometry(assuming2:1ellipsoidaspectratios),
we tested approximately 600 model variations in upper and lower
plutonsizes.For10–20-km-diameterupperplutons,solutionsforthe
lower body fall within a narrow trade space, with diameters of 47 km
and 57 km (Methods). Our end-member model retains the upper GC
pluton as 13 km in diameter at 1-km depth, which will minimize the
volumeofthelowerbody,providingalowerlimitforitssize.Weobtain
a best-fit surface heat flux for a lower body with GB concentration at
about 53 km in diameter at about 7.5-km depth (centred at 20.5-km
depth; Methods). The resulting heat flux peaks at 180 mW m−2
, mak-
ingthisthehighestdetectedheatfluxontheMoon,approximately20
times the 5–10 mW m−2
highlands background3
. Figure 2d shows our
end-member model heat flux (in orange, with the heat for the upper
and lower pluton shown in blue and red), Fig. 2e shows the resulting
Tb at each frequency and Fig. 2f shows the resulting TA for the two
antenna models. Figure 3 shows the same curves in Fig. 2f compared
with the Chang’e data as a function of distance from the centre of the
CBVC.Thetwobodiesinthisend-membermodelrepresentupto1.7%
of the total lunar Th budget estimated from surface concentrations3
.
This is not unique, and this model depends on assumed radiogenic
concentrations and pluton shapes, but serves as a first-order model.
Amodelassumingnoheatproductionfromtheupperplutonresultsina
poorfit,butresultsinalowerbodythatisstillunder60 kmindiameter,
providinganupperlimitonthesizeofCompton–Belkovichbatholith
(assuming GB composition; Methods).
Figure4illustratestheresultingtemperatureandheatfluxfromour
end-membermodelledpluton.InFig.4b–d,wefindapeaktemperature
–30
–20
–10
20 20
0 0
–20 –20
–50 –25 0 25 50
Distance from centre (km)
0
10
20
30
40
50
Depth
(km)
200
300
400
500
600
700
800
0 200 400 600 800 1,000 1,200
0
10
20
30
40
50
Uneffected crust
50 km from centre
Centre
–50 –25 0 25 50
Distance from centre (km)
0
10
20
30
40
50
Depth
(km)
50
100
150
Depth
(km)
80º E 120º E
100º E
57º N
65º N
65º N
57º N
65º N
65º N
80º E 120º E
100º E
Breadth (km)
Width (km)
Depth
(km)
Temperature (K)
Temperature
(K)
Heat
flux
(mW
m
–2
)
Lower pluton:
53 × 26.5 km
10.4 μW m–3
69.7-ppm Th
7.5-km deep
Upper pluton:
13 × 6.5 km
22 μW m–3
132-ppm Th
1-km deep
a b
c d
e f
50 km
Longitude
Latitude
Longitude
Latitude
250 mGal
0 mGal
50 km
250 mGal
0 mGal
Fig.4|GeophysicalmodelsoftheCompton–Belkovichbatholith.a,b,Our
end-memberCompton–Belkovichplutonmodelbasedonfittingofthesurface
heatfluxenhancement(a)andtheresultingheatflux(b).c,d,Thesubsurface
temperaturespredictedbythismodelasafunctionofdepth(c)andcross
section(d).e,f,GRAILBouguergravity(inunitsofmGal)oftheCBVCregion
(e)andGRAILBouguergravityafterremovingthegravitysignatureofamodel
fromthemiddleofourpreferredrange(f;90 kg m−3
densityanomalyforthe
lowerbody).TheCBVCgravityanomalyassociatedwiththisplutonsitsonthe
shoulder(smallcircle)ofabroaderandhighermagnitudeanomalyassociated
withthelargerCompton–Belkovichregion.
5. 120 | Nature | Vol 620 | 3 August 2023
Article
of867 Kwithinthelowerpluton,placingitbelowtheliquidusatpresent,
butfeasiblymolteninthepast.Heatsourcesassumingquartzmonzo-
diorite(GA composition)requiredbodiesthescaleoftheentire50-km
crustal column and would result in a much wider surface expression.
Deeper, larger GB concentration bodies also produce a more laterally
extensivesurfaceheatfluxthanisconsistentwiththedata,againrequir-
ingamid-crustalheatsource.Thisheatfluxcouldwarmnighttimesur-
facetemperaturesbyabout1 K,butwecannotdetectthissignalamong
effectsoflocaltopographyandalbedoinLRODivinerdata(Methods).
GRAIL Bouguer gravity data reveal a narrow positive gravity anom-
aly centred on and comparable in scale to the microwave brightness
anomaly on the shoulder of the broader Compton–Belkovich region
Bouguergravityhigh.Althoughitisimpossibletouniquelyconstrain
thedensitystructureowingtothelargeregionalgravityanomalies,we
cantestwhethertheend-memberplutonmodelisconsistentwiththe
observedgravity.Themodelledgravityarisingfromthisplutonmodel
matchestheobservedanomalyfordensitycontrastsofthelowerbody
rangingfrom60 kg m−3
to120 kg m−3
relativetothesurroundings,with
the density anomaly of the upper body assumed to be half that of the
lower body. These density contrasts equate to absolute densities of
2,940–3,000 kg m−3
and 2,470–2,500 kg m−3
for the lower and upper
bodies, respectively, based on a linear density model for the farside
highlands26
. Assuming a low porosity, the density of the lower body
implies a material that is somewhat less dense than typical mare27
,
consistent with a slightly more silicic composition, whereas the low
densityoftheupperbodysuggestsamoreevolvedandsilicicintrusion.
Figure 4e,f shows the effect of removing the gravity anomaly from a
model assuming a 90 kg m−3
density anomaly for the lower batholith
from the observed gravity.
These data solidify the conclusion that Compton–Belkovich is the
resultoffelsicvolcanismandprovideevidenceforanevolvedmagma
plumbing system much larger than expected on the Moon1,5,8,9,15,28
. A
magmatic system of this size requires one of the following features:
(1)along-livedthermalsource,suchasafarsidemantleplume(which
appears in some models29
), to facilitate multi-stage magmatic pro-
cessing; (2) an anomalously wet pocket of the otherwise dry Moon
(consistentwithCBVCvolcanicestimatesof2 wt%water17
),whichcould
lower the local melting point; or (3) a farside KREEP (potassium (K),
rare-earth elements (REE) and phosphorus (P) rich) layer that could
build sufficient radiogenic material to remelt through self-heating.
All scenarios imply large-scale compositional heterogeneities in the
mantle and/or crust during lunar formation.
Petrogenesis of lunar granites, felsites and quartz monzodiorites
is subject to ongoing debate centred around four models: (1) differ-
entiation driven by silicate–iron liquid immiscibility30,31
; (2) remelt-
ing of lunar crust in large impact events32
; (3) crystal fractionation
of KREEP basaltic liquids33–35
; and (4) partial melting of KREEP-rich
monzogabbro and alkali gabbronorite crust8,36
. Hypothesis 1 is pre-
cluded at the CBVC owing to the large volume needed as well as lack
ofcorrelationbetweenhighThcontentsandalargepositiveBouguer
gravity anomaly, as Th would fractionate into the denser, iron-rich
component36
. The system’s geometry required to accommodate the
observed heat-flow anomalies precludes hypothesis 2. Thus, both
remaining scenarios, or probably a combination of the two, require
the initial presence of a farside KREEP component to form the CBVC
system.Thedistillationofradiogenicelementsviaremeltingorcrystal
fractionationfromKREEPcomponentsisneededtoachievetheUand
Th compositions that produce the observed heat-flow feature. The
KREEP-rich material beneath Compton–Belkovich may represent a
localthickeningofaformercontinuousfarsideKREEPlayerorarelict
patchofKREEPleftbehindafteragloballayerwasremobilizedtothe
nearside37,38
.
Furthermore, this work illustrates a new tool for mapping a plan-
etary geothermal gradient from orbit through passive microwave
radiometry, which can provide a window into crustal and interior
heat-producing structures. The high heat flux and relatively low-loss
materialatCompton–Belkovichallowedthemultipleshortwavelengths
oftheChang’einstrumentstouniquelyconstrainthegeothermalflux.
Longer wavelengths will be required to map the lower heat flux seen
overmostoftheMoonandotherbodies,highlightingapathforwardsin
futurespacecraftinstrumentation.Suchdatashouldbeground-truthed
ontheMoonbyagloballydistributedheatfluxnetwork17,39
.Techniques
such as in situ heat flux, seismic, electromagnetic, long-wavelength
radarexplorationandsamplegeochemicalanalysiscouldfurtherchar-
acterizethepresence,sizeandoriginoftheCompton–Belkovichpluton
system.Ourresultsconcludethatthisisahighlyevolved,multi-stage,
batholith-scale,graniticmagmaticsystem—aphenomenonpreviously
documented only on Earth.
Onlinecontent
Anymethods,additionalreferences,NaturePortfolioreportingsumma-
ries,sourcedata,extendeddata,supplementaryinformation,acknowl-
edgements, peer review information; details of author contributions
andcompetinginterests;andstatementsofdataandcodeavailability
are available at https://doi.org/10.1038/s41586-023-06183-5.
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7. Article
Methods
Instrumentbackgroundandlosstangentmaps
The MRM instruments carried by CE-1 and CE-2 made measurements
in four spectral channels (3.0 GHz, 7.8 GHz, 19.35 GHz and 37 GHz)40
.
TheCE-1datahavechannel-dependentresolutionsofabout35–50 km
from its orbital altitude of about 200 km, whereas the CE-2 data have
resolutionsofabout17.5–25 kmbecauseitsorbitalaltitudewasabout
100 km. The microwave observations have been used to estimate
regolith thickness41
, dielectric properties18,19,42
, rock abundance43,44
,
subsurfacetemperatures45
andgeothermalheatflow46,47
aswellasthe
eruptionphaseofbasalticvolcanisminthemareoftheMoon48
.Inthe
polar region, MRM data analysis usually focuses on searching for evi-
dence of water ice49
and studying the thermal gradient50
.
A quantity known as the dielectric loss tangent, tan δ, controls the
depth from which microwave energy is emitted. This is simply the
ratiobetweenthereal,ε′,andimaginary,ε″,dielectricconstants,with
tan δ = ε″/ε′. Extended Data Fig. 1 shows the mapped ‘integrated loss
tangent’, or average loss tangent over the depth sounded by a given
frequency as described in ref. 19. These maps are based on diurnal
microwave amplitudes, increasing with higher loss as soundings are
closer to the surface. Diurnal amplitudes are fit using all data within
a 1/4° box of each point. As discussed in refs. 18,19, there appear to
be substantial offsets in the absolute temperature calibration of the
Chang’e data, but the relative calibration (comparing location to
locationordiurnalamplitudes)appearsrobustandinalignmentwith
modelexpectations.Allworkinthispaperreliesonrelativecalibration
(for example, how hot Compton–Belkovich is compared with its sur-
roundingsatagivenfrequency).ThestripinginExtendedDataFig.1is
owingtovariabletimeofdaycoverageinproducingafittothediurnal
amplitude.
Fromthesemaps,wearguethatthereisnolossanomalyassociated
withtheCompton–Belkovichfeaturethatcouldexplaintheenhanced
TA.FeaturessuchasDugan J(thesmall,freshcraterdirectlytotheeast
ofCBVC)orComptoncrater(thelargecrateratabout57° N,104° E)have
ahigherloss.Theapparentlow-lossareasonhigh-latitudecratersresult
fromlowamplitudesowingtotopographicshadowingnotaccounted
forinthesefits.ExtendedDataFig.1illustratestheaverageintegrated
losstangentforCBVC(black)andtheentiremapinExtendedDataFig.1
(red) compared with the highlands terrain model from ref. 19 (blue
line). However, a high loss would decrease the apparent heat flux, not
increase it—making our heat flux estimates a lower limit.
On this basis, we use the Extended Data Fig. 1 loss tangent maps to
derive appropriate microwave weighting functions, w, which relates
the physical temperature versus depth, T(z), to the microwave Tb at
a given frequency under nadir observation as ∫
T w z T z z
= ( ) ( )d
b 0
∞
. The
discreteformis ∑
T wT
= i
n
i i
b =1 ,wherenisthetotalnumberoflayers.Ti is
the physical temperature of layer i and wi is the effective weighting
function,whichhasbeenconvolvedwiththicknessdi.Inanon-scattering
medium based on refs. 51,52, wi can be expressed as:
∏
w Γ R R
= (1 − )(1 − e )(1 + × e ) × ((1 − )e ) (1)
i
κ d
i i
κ d
j
i
j j
κ d
−
( +1)
2 −
=1
( +1)
2 −
i i i i j j
∣ ∣ ∣ ∣
where Γ is the surface reflectivity and κi is the power absorption coef-
ficientoflayeri,di isthelayerthicknessandRi(i+1) isthereflectioncoef-
ficientbetweenlayeriandlayeri + 1,andjrepresentsthelayersbetween
iandthesurfacewithintheproductintegration,∏.Fornadirobserva-
tions(nooff-nadirdataisusedinthispaper),Ri(i+1) isgivenfromthereal
dielectric constant of the layer such that:
R
ε ε
ε ε
=
′ − ′
′ + ′
(2)
i i
i i
i i
( +1)
+1
+1
the power absorption coefficient, κi, is given by:
κ
f
c
ε
δ
= 2
2π ′
2
( 1 + tan − 1) (3)
i
2
1/2
where f is the frequency, c is the speed of light, ε′ is the real dielectric
constant (which we set as 1.92ρ
(ref. 53), for density, ρ) and tan δ is the
losstangent.κi determinesthepenetrationdepthofmicrowaveradia-
tion. As physical temperature amplitudes decrease with depth and
loss changes the depth being sensed, the diurnal amplitude of Tb can
beusedtocalculatetheκi anddielectricloss(seedetailsinrefs.18,19).
Antennamodel
The model TA results from a convolution of the emitted Tb from the
Moonandtheinstrumentantennapattern.Duringthegroundcalibra-
tiontestfortheCE-1system,theantennapatternsofthefourchannels
were measured54
. In this study, we fitted the antenna pattern of four
channels in a Gaussian form based on published parameters. These
parameters provided constraints on the main beam and the 3-dB effi-
ciencyandbeamwidth.Asthemainlobecontributes>68%ofthetotal
signalatallfrequencies54
,weconsideronlythemainlobeandthefirst
side lobes, which are treated as secondary Gaussians. CE-1 MRM and
CE-2 MRM are almost identical, so the same angular antenna radia-
tion pattern is used for both datasets. Extended Data Fig. 2 gives the
modelledantennapatternsoffourfrequencies.Forsimplicity,wehave
assumed symmetric antenna patterns, but in reality, there are small
differences in the E and H plane beam width.
This multi-frequency, multi-altitude fit allows for the constraint of
a unique source function of the emitted heat from the surface. These
patterns result in a different area in the instrument footprint filled
with the CBVC heat source at each frequency. For example, the spa-
tial footprint (generally defined by the 3-dB values) is approximately
25 km for CE-2 at 3 GHz and 17.5 km for the remaining channels. For
CE-1 (approximately at twice the orbital altitude), this is 50 km and
35 km,respectively.Thiswillcauseasmearingofanyheatsourcethat
is dependent on frequency and altitude.
Asdiscussedinthefollowingsection,weperformsomesimplepro-
cessing of the Chang’e data, such as latitude correction. We do not
otherwise change the data from the available TA values in the Chang’e
archive (included in the supplementary data) for effects such as foot-
print resolution, but instead process only our forward model of Tb to
createamodelTA.Also,asdiscussedinthefollowingsection,weuseour
antenna pattern and a thermal model for the CBVC region to produce
a forward model of the TA that should be observed from solar heating
alone.WethencansubtractthisfromthedatatocreateamapofTAthat
isideallysolelyfromincreasesingeothermalheat.Wethenproducefor-
wardmodelsofgeothermalheatingfromourplutonmodels(Extended
DataFig.3)toproduceamapofsurfaceheatflux.Cross-sectionsofour
end-membermodelheatfluxareshowninFig.2d.Wethenconvertthis
toaTbsignal(Fig.2e)includingaconvolutionwiththeantennapattern
foragivenfrequency,withtheresultingTAasshowninFigs. 2fand3.
As shown in Fig. 2c, there is an approximately linear relationship
between the Tb and the geothermal gradient at any given frequency.
For the highlands average loss tangent19
, this relationship follows as
(for a heat source, HF, in units of W m−2
):
Tb_3G = −89.24 × HF2
+ 166.2 × HF − 1.294
Tb_7.8G = −24.23 × HF2
+ 79.14 × HF − 0.6259
Tb_19G = −8.118 × HF2
+ 43.94 × HF − 0.3494
Tb_37G = −4.520 × HF2
+ 31.17 × HF − 0.2482
Ten-percent changes in the loss tangent will result in fits plotted as
dashed lines in Fig. 2c. This relationship assumes a background heat
flux of 8 mW m−2
, which was a reasonable expectation for this region
based on the crustal heat production models shown in Fig. 4.
We then perform some straightforward processing of the Chang’e
data,suchaslatitudecorrection,asdiscussedinthefollowingsections.
8. Alsoasdiscussedinthefollowingsection,weuseourantennapattern
andathermalmodelfortheCBVCregiontoproduceaforwardmodel
of the TA that should be observed from solar heating alone. We then
can subtract this from the data to produce a map of TA that is ideally
solelyfromincreasesingeothermalheat.Finally,weplottheTAmodels
fromgeothermalheating(fromFig.2d–f)againstthedata(corrected
for latitude) in Fig. 3.
Dataprocessing
To produce mapped values of microwave Tb, we interpolated the
raw data points of MRM measurements into gridded data map. This
is the same process used in refs. 18,19 and produces approximately
1/4°-resolution maps for the CE-2 MRM data. These data are shown in
a time series in Extended Data Fig. 3a, which shows that the CBVC is
hotterthanthesurroundingsatalllocaltimesatallfrequencies.These
data are shown as a noontime map in Extended Data Fig. 3b. These
maps highlight the CBVC hotspot, but it is not necessarily larger than
variationsowingtotopography.Wethenremovetopographiceffects
withmodelsoftheeffectsofsolarillumination.CE-1datawillproduce
asimilarmapatlowerresolutionwithalessapparentriseattheCBVC.
WeshouldnoteherethattheabsolutevaluesoftheseTbarenotaclear
matchtomodelexpectationsgiventhecurrentlyavailablecalibration
of the Chang’e MRM data. This has been noted in many publications
and discussed in detail in refs. 18,19. However, relative changes in Tb
arewellwithinlineofmodelexpectations.Therelativepoint-to-point
data comparison we rely on here (CBVC is hotter than the adjacent
area) is quite robust.
Taking advantage of the well calibrated relative Tb variations, or
ΔTb, we can have confidence in maps removing average trends for a
given latitude, albedo, slope, loss tangent and so on. The simplest of
those corrections is to remove the Tb trend as a function of latitude.
Forthis‘correction’,wesimplytakeandlongitudinalaverageoverdata
from a relatively crater-poor section of the data (104–112° longitude)
in Extended Data Fig. 3b, then smooth it (averaged over 200 pixels,
or about 1° latitude) to obtain a roughly linear trend as a function of
latitude. Extended Data Fig. 3c illustrates how this correction alone
makescleartheabnormalityoftheCBVCsite.Thisismostapparentin
the3-GHzdata,showingthelargestrelativechangefromasubsurface
heat source. Most other features in the region are clearly related to
topography, such as crater rims.
ForwardmodelofTbowingtosolarilluminationand
topography
ToimproveonourabilitytofittheChang’edatawithauniqueCBVCheat
fluxsource,weproduceaforwardmodelofexpectedmicrowaveemis-
sion from the region without an anomalous geothermal heat source.
We solve the heat diffusion equation for each location at the CBVC
and nearby regions using a standard finite-difference approximation
described in ref. 55 to model the lunar surface and subsurface tem-
perature. We include effects of latitude, slope, slope azimuth, rock
abundance, albedo and density profiles (characterized by the scale
heightofdensityorHparameter).Wethenuseavailableslope,azimuth,
density and albedo data to pick the appropriate temperature from a
databaseofpre-runone-dimensionalthermalmodels.Thisisnotafull
three-dimensional model in which facets exchange radiation as the
authors used previously for studying polar regions50,56–59
, but more
akin to the models presented in refs. 19,55.
We modelled temperatures based on local slope, x, and azimuth
angle,γ(radiansfromnorth)computedfromthegriddedLunarRecon-
naissanceOrbiterCamera(LROC)digitalelevationmodel.Inthetem-
perature calculations, local time t (lunar hour 0 to 24) was adjusted
based on the east–west component of the slope:
t t x γ
′= +
12 h
π
tan ( sin )
−1
and latitudes ϕ were adjusted based on the north–south component
of the slope
φ φ x γ
′ = +
180°
π
tan ( cos )
−1
The normal bolometric bond albedo quantifies the total solar
radiation reflected by the lunar surface. The effective solar flux
received by the lunar surface, Fe, can be expressed as: F A F
= (1 − ) =
θ
e
A θ S φ
(1 − ( + 1 − cos )) cos
0
0.2752
, where F = Scosϕ, θ is the solar inci-
dence angle,Sisthesolarconstant(1,361 W m−2
),ϕisthelatitudeand
A0 isthenormalbolometricbondalbedo.Inthisstudy,weuseauniform
best-fitalbedoof0.12fortheentireCBVCregion.Ifanything,thiswill
overestimate the solar heating contribution from the higher albedo
CBVC feature—but we treat such effects as negligible.
As the thermal conductivity is density dependent, in the ther
mal model, the density of regolith at depth z is described by:
ρ z ρ ρ ρ
( ) = − ( − )e z H
d d s
− /
, where ρs and ρd are the bounding densities at
the surface and at depths much greater than H (ρs = 1,100 kg m−3
and
ρd = 1,800 kg m−3
), respectively. The thermal conductivity of lunar
regolithusedinthethermalmodelis60,61
K ρ T K ρ χ T
( , ) = ( )[1 + ( /350) ]
c
3
,
where χ is radiative conductivity parameter and Kc(ρ) denotes the
contact conductivity, linearly proportional to density55,62
K ρ K K K
( ) = − ( − )
ρ ρ
ρ ρ
c d d s
−
−
d
d s
,whereKs andKd arethecontactconductivity
values at the surface and at depth, respectively.
Diviner rock abundance represents the fraction of a pixel covered
by rocks larger than about 1 m in diameter. Fundamentally, rock has
higher thermal inertia, so it is warmer at night. The contribution of
infrared spectral radiance from rocks is given by
I λ T ε
hc
λ
( , ) =
2
e − 1
hc
λkT
rock rock
2
2
−1
rock
where Trock is the physical temperature of rocks, k is the Boltzmann
constant,histhePlanckconstant,cisthespeedoflightinthemedium,
εisemissivityandλisthewavelength.Foreachpixelwitharockfraction
of f, the infrared spectral radiance is:
I f I fI
= (1 − ) +
regolith rock
Thenthephysicaltemperatureofeachpixeliscalculatedfrominfra-
redspectralradiance.Byapplyingthethermalmodel,eachlocation’s
surfaceandsubsurfacetemperatureattheCBVCarecalculated.Mod-
elledbrightnesstemperaturesatfourfrequenciesbeforeconvolution
are shown in Extended Data Fig. 4.
The modelled Tb at four frequencies after convolution with our
antenna models are shown in Extended Data Fig. 5. As these models
donotincludereflectedradiation,areassuchasHaynCrater(northwest
corner) are colder than in reality.
ThisforwardmodelshouldbearastrikingresemblancetoExtended
Data Fig. 3b if produced properly. This is illustrated in Extended Data
Fig.6,whichshowsthedatainExtendedDataFig.3bminusthemodel
inExtendedDataFig.5.Althoughsomeresidualsexist,especiallyinthe
high-frequency models, most features in the CBVC region and about
61°-latitude band have been removed. These models are then used to
produceFig.3.Inthatfigure,weplotalldatainthesemapsasafunction
of distance from the centre of the CBVC for convolutions using both
the CE-1 and CE-2 orbital altitudes.
Extended Data Fig. 6 also illustrates the coincidence between the
microwave Tb enhancement and the derived Lunar Prospector Th
enhancementthatledtothediscoveryofCompton–Belkovich4
.Here
we can see a clear spatial correlation between the heat flux anomaly
and the Lunar Prospector Neutron Spectrometer (LPNS) Th, which
is also illustrated in Extended Data Fig. 6e, which shows the inverse
picture, with mapped pixon-reconstructed Th values7
and contours
9. Article
of 3-GHz ΔTb values. However, the directly derived Th concentration
(about 7 ppm from the pixon reconstruction; Extended Data Fig. 6e)
and even the remodelled surface Th concentration (according to
ref. 7, is 14–26 ppm) is far too low of a radiogenic concentration to
explaintheapproximately180 mW m−2
heatfluxrequiredbyourdata.
Petrologicparameters
Noting that the surface Th concentrations are too low to explain the
heatfluxobservedattheCBVC,weusegeomorphologyandlunarsam-
ple petrology to provide reasonable starting points for a heat source
model.
The geomorphology of the CBVC is consistent with a volcanic cal-
dera9–12
thatexperiencedpiston-stylecollapsewherethecalderafloor
faulted downwards in a fairly coherent block. This style of collapse
formsaboveellipsoidal,shallowlyemplacedmagmachambers63
whose
depth is less than the horizontal dimension64
. Using the vents within
the ring faults as a means to constrain the structural diameter of the
caldera12
,themagmachamberispredictedtobeabout13 kmindiam-
eter, probably being composed of smaller bodies, but having the net
effect of a single heat source. Petrologic modelling of lunar granites
constrains the upper magma emplacement depth to approximately
1 km(refs.2,36).Theseparametersguideourpreferredmodel,which
assumesasimplified2:1ellipsoid13 kmindiameter(6.5-kmthick)and
a larger chamber below.
Three generalized granite families found in the Apollo returned
sample collection can serve as reasonable estimates of the range of
compositionsthatmayexistontheMoon.Asnoted,thedatapresented
herestronglysupportascenarioofpartialmeltinganddifferentiation
of KREEP-rich rocks. Indeed, although the deeper emplaced pluton
is less enriched in radiogenic elements (about 60-ppm Th) than the
upper, smaller pluton (about 132-ppm Th), this body still has Th con-
centrations much higher than the Apollo KREEP basalt samples. The
enrichment from Apollo KREEP basalt concentrations to those of the
modelled lower body are consistent with a partial melting and frac-
tionationevolutionthatwouldachievequartzmonzodioritetogranite
compositions.Thus,thelowerbodycouldformfromextensivecrystal
fractionationofaKREEPbasaltparentmeltorasaresultofpartialmelt-
ing of a KREEP-enriched monzogabbro or alkali gabbronorite lower
crust.Likely,anellipsoidallowerbodysimplifiesacomplexmagmatic
architecture (Extended Data Fig. 7).
The presence of a more evolved upper body suggests a multi-stage
process wherein more evolved melts were extracted and segregated
effectivelyfromthelowermagmachamber.Repeatedextractionand
furthercrystalfractionationofincompatibleelement-enrichedsilicic
magmas would enable the formation of the upper magma chamber.
Detailsoffinite-elementforwardmodels
Ourend-membermodelofthe13-km-diameterupperplutonand53-km
lower pluton is not a unique solution, but is based on patterns seen in
528 example model runs. These steady-state models were produced
using a Comsol Multiphysics finite-element heat conduction model
to enable changes in density and properties as a function of depth. A
steady state should be a safe assumption as the last eruptions of the
CBVCwereprobablymorethan3.5 billionyearsago65
.Weapproached
themodelswithfixedparametersdesignedtominimizethesizeofboth
heat-producing bodies. These include:
(1) Foremost, we fixed the radiogenic heat production of both bod-
ies. The upper pluton is limited to a heat production of 22 μW m−3
,
consistent with the highest Th concentration granite found in the
lunarsamplecollection,describedhereastypeGC.Althoughitmay
be true that the CBVC has an even higher concentration of radio-
genic materials, we did not think it was reasonable to go beyond
thismeasuredvalue.Thelowerplutonwasthenfixedat10.4 μW m−3
heatproduction,consistentwithmanymoderateThconcentration
granites, or type GB.
(2) Weforcedthebodiestobeasclosetothesurfaceaswefeltplausible.
Theupperplutonwasrequiredtobeat1-kmdepthwiththenominal.
However, it is a somewhat arbitrary idea that this overburden is
neededtohavepreventedtheentireplutonfromerupting3.5 billion
yearsago.Movingtheupperplutonclosertothesurfacewouldnot
increaseheatfluxmarkedly,mainlyaffectingthewidthofthepeak
wellbelowMRMspatialresolution.Weputthelowerplutonasnear
tothesurfaceaspossible,soitwasalwaysjusttouchingthebottom
oftheupperpluton.Thelowerplutoncanbeplaceddeeper,butthis
would require the lower pluton to be larger to produce the same
surface heat flux and result in a spatially wider signal than seen.
(3) Weforcedthebodiestobeellipsoids,circularinthex–yplane,with
a2:1aspectratio.Again,thisneednotbethecase,butthisshapeis
areasonablefirst-ordermodel.Wenotethatthehorizontaldimen-
sions of the bodies is constrained by the spatial pattern of the Tb
anomaly, but there will be a trade-off between the best-fit vertical
dimension (or aspect ratio) and assumed heat production.
We approached fitting the models to the data by running a suite of
176 diameter combinations of the two bodies. The upper body was
allowedtovarybetween10 kmand20 kmindiameter,withlimitssetby
thegeometryofthesurfacetopographicfeature.Wealteredthelower
bodybetween45 kmand60 kmindiameter.These176modelswererun
with three different density profiles and related thermal conductiv-
ity using the nominal density and conductivity profiles discussed in
ref. 21. These assume an exponential density profile that increases
density by a factor of e over a scale height of 1 km, 5 km and 10 km,
consistent with GRAIL analysis66
. The granites were given a thermal
conductivityof3.1 W m−1
K−1
(ref.67).Heredensityofthegranitebodies
is set to 2,550 kg m−3
.
Extended Data Fig. 8a illustrates the suite of model fits run to fit
the data following the three criteria listed above. These fits consider
onlythepeakheatproductionwiththeplottedvaluerepresentingthe
absolutevaluedifferencebetweenthepeakvalueinthedataversusthat
of the model. These plots are for the 5-km e-folding model, but show
similarresultstoothermodels(withbestfitsnotedbyanasterisk).The
upper plots show the sum of the misfit between the peak in data and
model for all four frequencies (for CE-1 and CE-2, respectively). The
lower plots omit 37-GHz data from this fit, as it was most prone to the
effects of surface temperature errors in the model.
Alltheplotsshowthatanarrowavenueofplutonmodelsminimizes
thedata–modeldifferences.Theminimumdata–modeldifferencefor
eachcrustaldensitymodelisplottedasacolouredasterisk,although
manyvaluesalongtheminimumavenuearenotablysimilar.TheCE-2
data show a greater tendency towards smaller lower pluton models
for large upper plutons owing to the fact its lower altitude shows less
lateral smearing. On the basis of surface faulting, we again favour a
smallerupper-plutonsource,leadingustowardsthisrange,whereall
fits favour a roughly 53–56-km-wide lower pluton.
TheplotsinExtendedDataFig.8bconsiderthebestfitoverthearea
±15 kmaroundthecentreofCBVC,againforthe5-kme-foldingmodel.
Here we again sum the difference between data and model (differ-
encing the lines from the data points in Fig. 3) over all frequencies,
hoping to capture more information on the fit to the overall shape of
the enhanced brightness temperature. These fits result in a slightly
wider‘best-fitavenue’withminimumrangesforthelowerplutonnow
centring around 52–55-km diameter. We do not plot minimum values
hereastheyoftenendedupwitha20-kmupper-bodydiameter,which
is hard to reconcile with the surface caldera geometry. Although it is
notunreasonablethatamagmasourcebodycurrentlyfillsadifferent
geometry than our chosen preferred 13-km-diameter, 6.5-km-thick
upperpluton,weusethatasaguideforourend-member13-km/53-km
upper-body/lower-body geometry.
ExtendedDataFig.9a,billustratesthesamemodelfitsasinExtended
Data Fig. 8b but with lower radiogenic concentrations in the upper
10. pluton.Althoughthe132-ppmsamplewasfoundinasmallclast,itisnot
believedtorepresentabulkradiogeniccompositionofalargerbodyon
the Moon. As we do not have samples from the CBVC, it is speculative
tosuggestthatsuchhighconcentrationsexistthere.Ourend-member
modelusedthishigh-ThGC concentrationassumptiontominimizethe
heat production required from the lower body. This case resulted in
anapproximately53-kmbest-fitdiameterforthislowerGB concentra-
tion ‘batholith’. In Extended Data Fig. 9a, we instead model the upper
pluton as also GB concentration; these fits result in a slightly larger
lowerbody,approximately56 kmindiametertoaidinaccountingfor
theextraheatflux.Itisnotedthattheslightlyhighervaluesonthe‘sum
thedifference’colourbarsdenotesthatthesefitsareworsethantheGC
assumption,probablypointingtoatrueupper-plutonconcentration
between GB and GC.
Extended Data Fig. 9b presents the extreme assumption, in which
the upper pluton is devoid of radiogenic material. This would be the
opposite ‘end member’, where all heat is coming from only a lower
body, meaning the upper pluton (argued for by fault and caldera
geometry) was fully evacuated. Here ‘diameter of the upper pluton,
DU’couldalsobelabelledasdepthtothetopofthelowerbody(where
depth = 1 km + DU/2).Thisrequireslargerlowerbodies,butstillunder
about 60 km (assuming GB concentrations). We note, however, that
the sum of the difference values is even larger, again pointing to the
need for an upper body.
This is evidenced primarily from the need for high peaks TA values
in the 19-GHz and 37-GHz channels. Without a highly concentrated
centralsource,thehigh-frequencydatashouldnothaveseensuchhigh
TAvalues.AssumingGC asanupperlimitforpotentialradiogeniccon-
centrationsontheMoonandthismodel,weconcludethatalowerbody
(againassumingGB concentrationsandsimpleellipsoidalshape)would
therefore fall between about 53 km and 60 km in diameter between
approximately7.5 kmand11 kmbelowthelunarsurface.Althoughthese
modelshavewiderangeofassumptions,theyprovideatheoreticalbasis
for the size of the system that must exist below the CBVC.
Gravityanalyses
We took gravity data from the GRGM1200 gravity model26
. Although
therank-minus-oneconstrainedfieldsofthatstudyprovideimproved
correlationsbetweenthefreeairgravityandtopographyouttodegree
1,200, we find that the resulting Bouguer gravity models show orbit
parallelstripingandothernoisebeyonddegree500inthisregion,and
so we limit our analyses to a degree 500 representation of the field.
The gravity from topography was calculated68
assuming a density of
2,500 kg m−3
(refs. 20,26) to calculate the Bouguer gravity.
As noted in the main text, the Bouguer gravity shows a distinctive
positive gravity anomaly centred on the Th-rich spot and microwave
Tb anomaly at the CBVC. However, this location also shows a positive
topography mound, consistent with either a volcanic construct or
upwarping of the crust above an intrusive body9
. This raises the pos-
sibility that the observed positive Bouguer gravity anomaly at this
locationissimplyaresultofanincorrectdensityassumedintheterrain
correction. We find that an assumed crustal density of 3,300 kg m−3
minimizes the CBVC’s distinctive positive gravity anomaly. However,
such a high density is at the high end of mare sample densities27
, is
greater than regional mare surface densities as constrained by grav-
ity26
and is incompatible with the inferred silicic surface composition
basedonLROdata9,11
.Asilicicvolcanicconstructismorelikelytohave
a density similar to the 2,500 kg m−3
value assumed for the surround-
ing lunar terrain69
.
Althoughthedatashowadistinctivepositivegravityanomalyassoci-
atedwiththeCBVC,itissuperposedontheshoulderofthebroaderand
larger-magnitudeBouguergravityhighassociatedwithalargedepres-
sion,consistentwitheitherisostaticallycompensatedthinnedcrust20
or
increaseddensityanddecreasedporosityowingtoaregionalthermal
anomaly70
. Given the small magnitude of the CBVC anomaly relative
tothisbroadergravityhigh,itisnotpossibletouniquelyconstrainthe
densitystructureofCBVCordirectlyinvertthegravityforthesubsurface
densitystructure.Moreover,withoutaddedconstraintsonthegeometry
ordensityofthesubsurfacebody,auniquesolutionisnotpossible.
Instead,wetestwhethertheend-memberplutonmodelisconsistent
withtheobservedgravity.Weforwardmodelthegravityarisingfrom
thepairofellipticalplutons,decomposingeachplutonintoalargenum-
berofrectangularprismaticelements71
,withahorizontalresolutionof
1 km and vertical resolution of 0.5 km. In preliminary tests, we found
thattheshallowsmallerbodyalonegeneratesanoverlysharpgravity
anomalyinconsistentwiththedata.Incomparison,thelargerdeeper
bodyproducesagravityanomalycommensuratewiththeobservations.
The end-member pluton model indicates a higher Th concentration
in the upper body, which would probably be associated with a more
evolved and more silicic composition, and, thus a lower density. We
imposetheconstraintthattheupperbodyhasadensitycontrastthatis
halfthatofthelowerbody,andthenforwardmodelthegravityarising
from both plutons, which is then subtracted from the data.
We find that density contrasts for the lower body in the range of
60–120 kg m−3
generate models that, when subtracted from the data,
largely remove the small-scale CBVC gravity anomaly, leaving behind
a smoother shoulder of the broader Compton–Belkovich feature
(ExtendedDataFig.10).Largerdensitycontrastsleavebehindanega-
tive anomaly at the CBVC, whereas smaller density contrasts do not
adequatelyremovetheCBVCgravityanomaly.Thedensitycontrastof
thelowerbodyof60–120 kg m−3
atadepthof20.5 kmwouldequateto
a density of 2,940–3,000 kg m−3
, based on a linear density model for
the farside highlands26
. Assuming a low porosity, this density implies
a somewhat less dense body than a typical mare27
, suggesting a more
silicic composition. The upper body has a smaller density contrast
relativetothelessdenseshallowcrust,equivalenttoadensityof2,470–
2,500 kg m−3
.Thislowdensityisconsistentwithamoreevolvedgranitic
pluton, as inferred based on the microwave data.
Weemphasizethatthegravitymodelsarenotunique,giventhevari-
ability of the field in this region and the inherent non-uniqueness of
potentialfielddata.However,giventhepreferredplutonstructureand
theobservedgravityanomaly,theconclusionthatthelowerintrusive
bodymusthaveamodestpositivedensitycontrastwhereastheupper
intrusivebodymusthaveaweakerdensitycontrastisrobust.Theupper
body thus requires a low absolute density given the vertical density
structure of the crust derived from GRAIL gravity data. The resulting
density models are consistent with the interpretations based on the
microwave data.
Inclusionandethics
The authors of this work have strived to provide an inclusive experi-
enceofallco-authorsregardlessofgender,careerstageornationality.
Dataavailability
Thedatausedtomakethefiguresinthispaperareavailableathttps://
doi.org/10.5281/zenodo.7786749.TheoriginalChang’e‐1andChang’e-2
MRM data can be downloaded from http://moon.bao.ac.cn/index_
en.jsp. Our group has also produced a readable global gridded data
productofallavailableChang’e-1andChang’e-2dataathttps://zenodo.
org/record/7790013. Source data are provided with this paper.
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AcknowledgementsThis work was funded through Lunar Data Analysis Grant 80NSSC20K1430
and work related with the Lunar Reconnaissance Orbiter Diviner Lunar Radiometer.
Author contributions M.A.S.: primary writing, central ideas and concepts, figures and
funding. J.F.: primary data processing, microwave modelling, writing, central ideas and data
interpretation. K.L.-F.: petrologic model synthesis, writing and figure creation. J.C.A.-H.: gravity
modelling, synthesis and writing. R.C.E.: petrologic model synthesis, writing and advised
K.L.-F. M.S.C.: lead data product production (of global maps), science discussions, detailed
review and editing. C.M.: aided in data product production (of global maps), science
discussions, detailed review and editing. J.W.H.: science discussions, detailed review and
editing. T.D.G.: science discussion, review and editing. M.N.W.: copy-editing and figure editing.
Competing interests The authors declare no competing interests.
Additional information
Supplementary information The online version contains supplementary material available at
https://doi.org/10.1038/s41586-023-06183-5.
Correspondence and requests for materials should be addressed to Matthew A. Siegler or
Jianqing Feng.
Peer review information Nature thanks David Lawrence and Sarah Valencia for their
contribution to the peer review of this work. Peer reviewer reports are available.
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