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.
Artigo relata como a Terra sofreu com os impactos de ateroides a 4 bilhões de anos atrás, e como a superfície do planeta foi remodelada e os oceanos formados.
Heterogeneous delivery of silicate and metal to the Earth by large planetesimalsSérgio Sacani
After the Moon’s formation, Earth experienced a protracted bombardment by leftover planetesimals. The mass delivered during
this stage of late accretion has been estimated to be approximately 0.5% of Earth’s present mass, based on highly siderophile
element concentrations in the Earth’s mantle and the assumption that all highly siderophile elements delivered by impacts
were retained in the mantle. However, late accretion may have involved mostly large (≥ 1,500 km in diameter)—and therefore
differentiated—projectiles in which highly siderophile elements were sequestered primarily in metallic cores. Here we present
smoothed-particle hydrodynamics impact simulations that show that substantial portions of a large planetesimal’s core may
descend to the Earth’s core or escape accretion entirely. Both outcomes reduce the delivery of highly siderophile elements to
the Earth’s mantle and imply a late accretion mass that may be two to five times greater than previously thought. Further, we
demonstrate that projectile material can be concentrated within localized domains of Earth’s mantle, producing both positive
and negative 182W isotopic anomalies of the order of 10 to 100 ppm. In this scenario, some isotopic anomalies observed in terrestrial
rocks can be explained as products of collisions after Moon formation.
Magnetic field and_wind_of_kappa_ceti_towards_the_planetary_habitability_of_t...Sérgio Sacani
We report magnetic field measurements for κ
1 Cet, a proxy of the young Sun when life arose on Earth. We carry out an analysis
of the magnetic properties determined from spectropolarimetric observations and reconstruct its large-scale surface magnetic
field to derive the magnetic environment, stellar winds and particle flux permeating the interplanetary medium around κ
1 Cet.
Our results show a closer magnetosphere and mass-loss rate of M˙ = 9.7 × 10−13 M yr−1
, i.e., a factor 50 times larger than the
current solar wind mass-loss rate, resulting in a larger interaction via space weather disturbances between the stellar wind and
a hypothetical young-Earth analogue, potentially affecting the planet’s habitability. Interaction of the wind from the young Sun
with the planetary ancient magnetic field may have affected the young Earth and its life conditions.
Artigo relata como a Terra sofreu com os impactos de ateroides a 4 bilhões de anos atrás, e como a superfície do planeta foi remodelada e os oceanos formados.
Heterogeneous delivery of silicate and metal to the Earth by large planetesimalsSérgio Sacani
After the Moon’s formation, Earth experienced a protracted bombardment by leftover planetesimals. The mass delivered during
this stage of late accretion has been estimated to be approximately 0.5% of Earth’s present mass, based on highly siderophile
element concentrations in the Earth’s mantle and the assumption that all highly siderophile elements delivered by impacts
were retained in the mantle. However, late accretion may have involved mostly large (≥ 1,500 km in diameter)—and therefore
differentiated—projectiles in which highly siderophile elements were sequestered primarily in metallic cores. Here we present
smoothed-particle hydrodynamics impact simulations that show that substantial portions of a large planetesimal’s core may
descend to the Earth’s core or escape accretion entirely. Both outcomes reduce the delivery of highly siderophile elements to
the Earth’s mantle and imply a late accretion mass that may be two to five times greater than previously thought. Further, we
demonstrate that projectile material can be concentrated within localized domains of Earth’s mantle, producing both positive
and negative 182W isotopic anomalies of the order of 10 to 100 ppm. In this scenario, some isotopic anomalies observed in terrestrial
rocks can be explained as products of collisions after Moon formation.
Magnetic field and_wind_of_kappa_ceti_towards_the_planetary_habitability_of_t...Sérgio Sacani
We report magnetic field measurements for κ
1 Cet, a proxy of the young Sun when life arose on Earth. We carry out an analysis
of the magnetic properties determined from spectropolarimetric observations and reconstruct its large-scale surface magnetic
field to derive the magnetic environment, stellar winds and particle flux permeating the interplanetary medium around κ
1 Cet.
Our results show a closer magnetosphere and mass-loss rate of M˙ = 9.7 × 10−13 M yr−1
, i.e., a factor 50 times larger than the
current solar wind mass-loss rate, resulting in a larger interaction via space weather disturbances between the stellar wind and
a hypothetical young-Earth analogue, potentially affecting the planet’s habitability. Interaction of the wind from the young Sun
with the planetary ancient magnetic field may have affected the young Earth and its life conditions.
Jupiter’s interior and deep atmosphere: The initial pole-to-pole passes with ...Sérgio Sacani
On 27 August 2016, the Juno spacecraft acquired science observations of Jupiter,
passing less than 5000 kilometers above the equatorial cloud tops. Images of Jupiter’s
poles show a chaotic scene, unlike Saturn’s poles. Microwave sounding reveals weather
features at pressures deeper than 100 bars, dominated by an ammonia-rich, narrow
low-latitude plume resembling a deeper, wider version of Earth’s Hadley cell. Near-infrared
mapping reveals the relative humidity within prominent downwelling regions. Juno’s
measured gravity field differs substantially from the last available estimate and is one
order of magnitude more precise. This has implications for the distribution of heavy
elements in the interior, including the existence and mass of Jupiter’s core. The observed
magnetic field exhibits smaller spatial variations than expected, indicative of a rich
harmonic content.
Jupiter’s interior and deep atmosphere: The initial pole-to-pole passes with ...Sérgio Sacani
On 27 August 2016, the Juno spacecraft acquired science observations of Jupiter,
passing less than 5000 kilometers above the equatorial cloud tops. Images of Jupiter’s
poles show a chaotic scene, unlike Saturn’s poles. Microwave sounding reveals weather
features at pressures deeper than 100 bars, dominated by an ammonia-rich, narrow
low-latitude plume resembling a deeper, wider version of Earth’s Hadley cell. Near-infrared
mapping reveals the relative humidity within prominent downwelling regions. Juno’s
measured gravity field differs substantially from the last available estimate and is one
order of magnitude more precise. This has implications for the distribution of heavy
elements in the interior, including the existence and mass of Jupiter’s core. The observed
magnetic field exhibits smaller spatial variations than expected, indicative of a rich
harmonic content.
The nonmagnetic nucleus_of_comet_67_p_churyumov_gerasimenkoSérgio Sacani
Artigo descreve como a sonda Rosetta e o módulo Philae descobriram que o cometa Churyumov-Gerasimenko não é magnetizado, contrariando uma teoria da formação do Sistema Solar.
Different Martian Crustal Seismic Velocities across the Dichotomy Boundary fr...Sérgio Sacani
Article This article is protected by copyright. All rights reserved.
Abstract
We have observed both minor-arc (R1) and major-arc (R2) Rayleigh waves for the largest marsquake (magnitude
of 4.7 ± 0.2) ever recorded. Along the R1 path (in the lowlands), inversion results show that a simple, two-layer
model with an interface located at 21 - 29 km and an upper crustal shear-wave velocity of 3.05 - 3.17 km/s can fit the
group velocity measurements. Along the R2 path, observations can be explained by upper crustal thickness models
constrained from gravity data and upper crustal shear-wave velocities of 2.61 - 3.27 km/s and 3.28 - 3.52 km/s in the
lowlands and highlands, respectively. The shear-wave velocity being faster in the highlands than in the lowlands
indicates the possible existence of sedimentary rocks, and relatively higher porosity in the lowlands.
Predictions of the_atmospheric_composition_of_gj_1132_bSérgio Sacani
GJ 1132 b is a nearby Earth-sized exoplanet transiting an M dwarf, and is amongst the most highly
characterizable small exoplanets currently known. In this paper we study the interaction of a magma
ocean with a water-rich atmosphere on GJ 1132b and determine that it must have begun with more
than 5 wt% initial water in order to still retain a water-based atmosphere. We also determine the
amount of O2
that can build up in the atmosphere as a result of hydrogen dissociation and loss.
We find that the magma ocean absorbs at most ∼ 10% of the O2 produced, whereas more than
90% is lost to space through hydrodynamic drag. The most common outcome for GJ 1132 b from our
simulations is a tenuous atmosphere dominated by O2
, although for very large initial water abundances
atmospheres with several thousands of bars of O2
are possible. A substantial steam envelope would
indicate either the existence of an earlier H2
envelope or low XUV flux over the system’s lifetime. A
steam atmosphere would also imply the continued existence of a magma ocean on GJ 1132 b. Further
modeling is needed to study the evolution of CO2
or N2
-rich atmospheres on GJ 1132 b.
Solar Interplanetary and Geomagnetic Activity in Solar Cycle 23ijsrd.com
The main features of solar cycle 23, sun enters a period of intermediate and weak solar activity in terms of sunspot number. Based on the observation from Omniweb data centre for solar- interplanetary data , geomagnetic activity and monthly mean count rate of cosmic ray intensity (CRI) variation data from Oulu / Moscow/ Keil neutron monitors (Rc=0.80 GV , Rc=2.42 GV and Rc=2.29 GV,) during solar activity cycle 23 . The phase of minimum solar activity began in May 2005 and lasted for 4.5 years the unprecedented duration of the relative sunspot numbers falls. It is observed that the strength of the interplanetary magnetic field has been falling off to new low levels, and reduces the GCR entering inner- heliosphere and it is also found that SSN positive correlated with Kp and Ap and sunspot number, 10.7 cm solar radio flux, were inverse correlated with monthly mean count rate of cosmic ray intensity.
Study of Solar Interplanetary and Geomagnetic Disturbances in Solar Cycle 23ijsrd.com
The most specific of solar cycle 23, sun enters a period of intermediate and weak solar activity in terms of sunspot number. Based on the observation from Omniweb data centre for solar- interplanetary data, geomagnetic activity and monthly mean count rate of cosmic ray intensity (CRI) variation data taken from neutron monitors during solar activity period 23/24. The phase of minimum solar activity began in May 2005 and lasted for 4.5 years the unprecedented duration of the relative sunspot numbers falls. It is observed that the strength of the interplanetary magnetic field has been falling off to new low levels, and reduces the GCR entering inner- heliosphere and it is also found that SSN positive correlated with Kp and Ap and sunspot number, 10.7 cm solar radio flux, were inverse correlated with monthly mean count rate of cosmic ray intensity.
Jupiter’s magnetosphere and aurorae observed by the Juno spacecraft during it...Sérgio Sacani
The Juno spacecraft acquired direct observations of the jovian magnetosphere and auroral
emissions from a vantage point above the poles. Juno’s capture orbit spanned the jovian
magnetosphere from bow shock to the planet, providing magnetic field, charged particle,
and wave phenomena context for Juno’s passage over the poles and traverse of Jupiter’s
hazardous inner radiation belts. Juno’s energetic particle and plasma detectors measured
electrons precipitating in the polar regions, exciting intense aurorae, observed
simultaneously by the ultraviolet and infrared imaging spectrographs. Juno transited
beneath the most intense parts of the radiation belts, passed about 4000 kilometers
above the cloud tops at closest approach, well inside the jovian rings, and recorded the
electrical signatures of high-velocity impacts with small particles as it traversed the equator.
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.
A study on severe geomagnetic storms and earth’s magnetic field H variations,...IJERA Editor
For our study, we have selected ten severe geomagnetic storms. Which occurred during the years 1994 to 2015. Here great geomagnetic storm of Dst index from -422 nT to -17 nT are taken. These storms are significant not only because of the extremely high magnetic activity but also due to their great impact on the geomagnetosphere. We have studied the relation between severe geomagnetic storms with Earth’s magnetic field in horizontal component (H constant) and also studied the relation between Dst index with sunspots number. The H constant data from Kyoto data centre and Dst index, Ap index, Kp index from OMNI data centre. We have found that the Dst is at very lowest level in this storm period, Ap index Kp index are increased in severe geomagnetic storm period and H Constant is at very lowest level in storm period. We have found that geomagnetic storms were induced to form the cyclones within 29 days. The Sunspots numbers are increased to induce to geomagnetic storm within 5 – 15 days
Direct evidence of substorm-related impulsive injections of electrons at MercurySérgio Sacani
Mercury’s magnetosphere is known to involve fundamental processes releasing particles and energy like at Earth due to the solar wind interaction. The
resulting cycle is however much faster and involves acceleration, transport,
loss, and recycling of plasma. Direct experimental evidence for the roles of
electrons during this cycle is however missing. Here we show that in-situ
plasma observations obtained during BepiColombo’s first Mercury flyby reveal
a compressed magnetosphere hosts of quasi-periodic fluctuations, including
the original observation of dynamic phenomena in the post-midnight, southern magnetosphere. The energy-time dispersed electron enhancements support the occurrence of substorm-related, multiple, impulsive injections of
electrons that ultimately precipitate onto its surface and induce X-ray fluorescence. These observations reveal that electron injections and subsequent
energy-dependent drift now observed throughout Solar System is a universal
mechanism that generates aurorae despite the differences in structure and
dynamics of the planetary magnetospheres.
Similar to Mars surface radiation_environment_measured_with_curiosity (20)
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.
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.
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.
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.
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.
X-rays from a Central “Exhaust Vent” of the Galactic Center ChimneySérgio Sacani
Using deep archival observations from the Chandra X-ray Observatory, we present an analysis of
linear X-ray-emitting features located within the southern portion of the Galactic center chimney,
and oriented orthogonal to the Galactic plane, centered at coordinates l = 0.08◦
, b = −1.42◦
. The
surface brightness and hardness ratio patterns are suggestive of a cylindrical morphology which may
have been produced by a plasma outflow channel extending from the Galactic center. Our fits of the
feature’s spectra favor a complex two-component model consisting of thermal and recombining plasma
components, possibly a sign of shock compression or heating of the interstellar medium by outflowing
material. Assuming a recombining plasma scenario, we further estimate the cooling timescale of this
plasma to be on the order of a few hundred to thousands of years, leading us to speculate that a
sequence of accretion events onto the Galactic Black Hole may be a plausible quasi-continuous energy
source to sustain the observed morphology
Connector Corner: Automate dynamic content and events by pushing a buttonDianaGray10
Here is something new! In our next Connector Corner webinar, we will demonstrate how you can use a single workflow to:
Create a campaign using Mailchimp with merge tags/fields
Send an interactive Slack channel message (using buttons)
Have the message received by managers and peers along with a test email for review
But there’s more:
In a second workflow supporting the same use case, you’ll see:
Your campaign sent to target colleagues for approval
If the “Approve” button is clicked, a Jira/Zendesk ticket is created for the marketing design team
But—if the “Reject” button is pushed, colleagues will be alerted via Slack message
Join us to learn more about this new, human-in-the-loop capability, brought to you by Integration Service connectors.
And...
Speakers:
Akshay Agnihotri, Product Manager
Charlie Greenberg, Host
State of ICS and IoT Cyber Threat Landscape Report 2024 previewPrayukth K V
The IoT and OT threat landscape report has been prepared by the Threat Research Team at Sectrio using data from Sectrio, cyber threat intelligence farming facilities spread across over 85 cities around the world. In addition, Sectrio also runs AI-based advanced threat and payload engagement facilities that serve as sinks to attract and engage sophisticated threat actors, and newer malware including new variants and latent threats that are at an earlier stage of development.
The latest edition of the OT/ICS and IoT security Threat Landscape Report 2024 also covers:
State of global ICS asset and network exposure
Sectoral targets and attacks as well as the cost of ransom
Global APT activity, AI usage, actor and tactic profiles, and implications
Rise in volumes of AI-powered cyberattacks
Major cyber events in 2024
Malware and malicious payload trends
Cyberattack types and targets
Vulnerability exploit attempts on CVEs
Attacks on counties – USA
Expansion of bot farms – how, where, and why
In-depth analysis of the cyber threat landscape across North America, South America, Europe, APAC, and the Middle East
Why are attacks on smart factories rising?
Cyber risk predictions
Axis of attacks – Europe
Systemic attacks in the Middle East
Download the full report from here:
https://sectrio.com/resources/ot-threat-landscape-reports/sectrio-releases-ot-ics-and-iot-security-threat-landscape-report-2024/
Transcript: Selling digital books in 2024: Insights from industry leaders - T...BookNet Canada
The publishing industry has been selling digital audiobooks and ebooks for over a decade and has found its groove. What’s changed? What has stayed the same? Where do we go from here? Join a group of leading sales peers from across the industry for a conversation about the lessons learned since the popularization of digital books, best practices, digital book supply chain management, and more.
Link to video recording: https://bnctechforum.ca/sessions/selling-digital-books-in-2024-insights-from-industry-leaders/
Presented by BookNet Canada on May 28, 2024, with support from the Department of Canadian Heritage.
Slack (or Teams) Automation for Bonterra Impact Management (fka Social Soluti...Jeffrey Haguewood
Sidekick Solutions uses Bonterra Impact Management (fka Social Solutions Apricot) and automation solutions to integrate data for business workflows.
We believe integration and automation are essential to user experience and the promise of efficient work through technology. Automation is the critical ingredient to realizing that full vision. We develop integration products and services for Bonterra Case Management software to support the deployment of automations for a variety of use cases.
This video focuses on the notifications, alerts, and approval requests using Slack for Bonterra Impact Management. The solutions covered in this webinar can also be deployed for Microsoft Teams.
Interested in deploying notification automations for Bonterra Impact Management? Contact us at sales@sidekicksolutionsllc.com to discuss next steps.
UiPath Test Automation using UiPath Test Suite series, part 4DianaGray10
Welcome to UiPath Test Automation using UiPath Test Suite series part 4. In this session, we will cover Test Manager overview along with SAP heatmap.
The UiPath Test Manager overview with SAP heatmap webinar offers a concise yet comprehensive exploration of the role of a Test Manager within SAP environments, coupled with the utilization of heatmaps for effective testing strategies.
Participants will gain insights into the responsibilities, challenges, and best practices associated with test management in SAP projects. Additionally, the webinar delves into the significance of heatmaps as a visual aid for identifying testing priorities, areas of risk, and resource allocation within SAP landscapes. Through this session, attendees can expect to enhance their understanding of test management principles while learning practical approaches to optimize testing processes in SAP environments using heatmap visualization techniques
What will you get from this session?
1. Insights into SAP testing best practices
2. Heatmap utilization for testing
3. Optimization of testing processes
4. Demo
Topics covered:
Execution from the test manager
Orchestrator execution result
Defect reporting
SAP heatmap example with demo
Speaker:
Deepak Rai, Automation Practice Lead, Boundaryless Group and UiPath MVP
PHP Frameworks: I want to break free (IPC Berlin 2024)Ralf Eggert
In this presentation, we examine the challenges and limitations of relying too heavily on PHP frameworks in web development. We discuss the history of PHP and its frameworks to understand how this dependence has evolved. The focus will be on providing concrete tips and strategies to reduce reliance on these frameworks, based on real-world examples and practical considerations. The goal is to equip developers with the skills and knowledge to create more flexible and future-proof web applications. We'll explore the importance of maintaining autonomy in a rapidly changing tech landscape and how to make informed decisions in PHP development.
This talk is aimed at encouraging a more independent approach to using PHP frameworks, moving towards a more flexible and future-proof approach to PHP development.
UiPath Test Automation using UiPath Test Suite series, part 3DianaGray10
Welcome to UiPath Test Automation using UiPath Test Suite series part 3. In this session, we will cover desktop automation along with UI automation.
Topics covered:
UI automation Introduction,
UI automation Sample
Desktop automation flow
Pradeep Chinnala, Senior Consultant Automation Developer @WonderBotz and UiPath MVP
Deepak Rai, Automation Practice Lead, Boundaryless Group and UiPath MVP
Let's dive deeper into the world of ODC! Ricardo Alves (OutSystems) will join us to tell all about the new Data Fabric. After that, Sezen de Bruijn (OutSystems) will get into the details on how to best design a sturdy architecture within ODC.
JMeter webinar - integration with InfluxDB and GrafanaRTTS
Watch this recorded webinar about real-time monitoring of application performance. See how to integrate Apache JMeter, the open-source leader in performance testing, with InfluxDB, the open-source time-series database, and Grafana, the open-source analytics and visualization application.
In this webinar, we will review the benefits of leveraging InfluxDB and Grafana when executing load tests and demonstrate how these tools are used to visualize performance metrics.
Length: 30 minutes
Session Overview
-------------------------------------------
During this webinar, we will cover the following topics while demonstrating the integrations of JMeter, InfluxDB and Grafana:
- What out-of-the-box solutions are available for real-time monitoring JMeter tests?
- What are the benefits of integrating InfluxDB and Grafana into the load testing stack?
- Which features are provided by Grafana?
- Demonstration of InfluxDB and Grafana using a practice web application
To view the webinar recording, go to:
https://www.rttsweb.com/jmeter-integration-webinar
Software Delivery At the Speed of AI: Inflectra Invests In AI-Powered QualityInflectra
In this insightful webinar, Inflectra explores how artificial intelligence (AI) is transforming software development and testing. Discover how AI-powered tools are revolutionizing every stage of the software development lifecycle (SDLC), from design and prototyping to testing, deployment, and monitoring.
Learn about:
• The Future of Testing: How AI is shifting testing towards verification, analysis, and higher-level skills, while reducing repetitive tasks.
• Test Automation: How AI-powered test case generation, optimization, and self-healing tests are making testing more efficient and effective.
• Visual Testing: Explore the emerging capabilities of AI in visual testing and how it's set to revolutionize UI verification.
• Inflectra's AI Solutions: See demonstrations of Inflectra's cutting-edge AI tools like the ChatGPT plugin and Azure Open AI platform, designed to streamline your testing process.
Whether you're a developer, tester, or QA professional, this webinar will give you valuable insights into how AI is shaping the future of software delivery.
Smart TV Buyer Insights Survey 2024 by 91mobiles.pdf91mobiles
91mobiles recently conducted a Smart TV Buyer Insights Survey in which we asked over 3,000 respondents about the TV they own, aspects they look at on a new TV, and their TV buying preferences.
Mars surface radiation_environment_measured_with_curiosity
1. Research Articles
13%, electrons ~1%, and about 1%
heavier nuclei (19, 20). Because of their
high energies, GCRs are difficult to
shield against, and can penetrate up to
several meters into the Martian regolith.
SEPs are produced in the solar corona
as a result of high energy processes
associated with flares, coronal mass
ejections (CMEs) and their correspond1
1
Donald M. Hassler, * Cary Zeitlin, Robert F. Wimmering shocks. SEP events are sporadic and
2
1
1
Schweingruber, Bent Ehresmann, Scot Rafkin, Jennifer L.
difficult to predict, with onset times on
3
4
5
2
Eigenbrode, David E. Brinza, Gerald Weigle, Stephan Böttcher,
the order of minutes to hours and dura2
2
2
2
Eckart Böhm,2 Soenke Burmeister, Jingnan Guo, Jan Köhler,
tions of hours to days. SEP fluxes can
6
7
Cesar Martin, Guenther Reitz, Francis A. Cucinotta, Myung-Hee
vary by several orders of magnitude,
8
9
1
10
Kim, David Grinspoon, Mark A. Bullock, Arik Posner, 4 Javier
and are typically dominated by protons,
11
4
Gómez-Elvira, Ashwin Vasavada, John P. Grotzinger, MSL
but composition can vary substantially
Science Team†
(21). SEP protons and helium ions with
1
ion energies below ~150 MeV/nuc
Southwest Research Institute, Boulder, CO, USA. 2Christian Albrechts University, Kiel, Germany. 3NASA
(“soft” spectrum events) are not able to
Goddard Space Flight Center, Greenbelt, MD, USA. 4Jet Propulsion Laboratory, California Institute of
Technology, Pasadena, CA, USA. 5Southwest Research Institute, San Antonio, TX, USA. 6German
penetrate to the Martian surface. TypiAerospace Center (DLR), Cologne, Germany. 7University of Nevada Las Vegas, Las Vegas, NV, USA.
cal column depths of the Martian at8
Universities Space Research Association, Houston, TX, USA. 9Denver Museum of Nature and Science,
mosphere at Gale Crater are on the
10
11
Denver, CO, USA. NASA Headquarters, Washington, DC, USA. Centro de Astrobiología (INTA-CSIC),
order of 20 g/cm2, thus energetic partiMadrid, Spain.
cles with energies less than ~150 MeV
*Corresponding author. E-mail: hassler@boulder.swri.edu
lose all of their energy before passing
through this amount of material. How†MSL Science Team authors and affiliations are listed in the supplementary materials.
ever, during “hard spectrum” events,
ions can be accelerated to energies well
The Radiation Assessment Detector (RAD) on the Mars Science Laboratory’s
above 150 MeV/nuc with substantial
Curiosity rover began making detailed measurements of the cosmic ray and
fluxes reaching the Martian surface. In
energetic particle radiation environment on the surface of Mars on 7 August 2012.
all events, secondary neutrons produced
We report and discuss measurements of the absorbed dose and dose equivalent
by SEPs in the atmosphere can reach
from galactic cosmic rays and solar energetic particles on the Martian surface for
the surface. The RAD measurements
~300 days of observations during the current solar maximum. These measurements
reported here cover observations of
provide insight into the radiation hazards associated with a human mission to the
GCRs as well as hard and soft SEP
surface of Mars, and provide an anchor point to model the subsurface radiation
events seen from the Martian surface.
environment, with implications for microbial survival times of any possible extant or
Together with the radiation environpast life, as well as for the preservation of potential organic biosignatures of the
ment results from RAD inside the Mars
ancient Martian environment.
Science Laboratory (MSL) spacecraft
during its cruise to Mars (22), these
The radiation exposure on the surface of Mars is much harsher than that measurements correspond to all three phases (outbound interplanetary
on the surface of the Earth for two reasons: Mars lacks a global magnetic journey, Mars surface stay, and return journey) of a human Mars mission
field to deflect energetic charged particles (1), and the Martian atmos- at this time in the solar cycle, and thus are directly relevant to planning
phere is much thinner (<1%) than that of Earth, providing little shielding for future human missions.
against the high energy particles that are incident at the top of its atmosIf Martian life exists, or existed in the past, it is reasonable to assume
phere. This environmental factor, for which there is no analog on Earth, it is or was based on organic molecules (23, 24), and will therefore share
poses a challenge for future human exploration of Mars (2–9), and is with terrestrial life the vulnerability to energetic particle radiation (25,
also important in understanding both geological and potential biological 26). Thus we present here extrapolations of the RAD surface dose measevolution on Mars. The radiation environment on Mars has been previ- urements (using transport models) to the Martian subsurface, with impliously estimated and modeled (10–17). Here we report in situ measure- cations for estimating lethal depths and microbial survival times (26–
ments of the ionizing radiation environment on the surface of Mars; 30). The radiation environment on Mars may also play a key role in the
these can be used to test and validate radiation transport models.
chemical alteration of the regolith and Martian rocks over geologic time
There are two types of energetic particle radiation incident at the top scales, affecting the preservation of organics including potential organic
of the Mars atmosphere, Galactic Cosmic Rays (GCRs) and Solar Ener- biosignatures of the ancient Martian environment (26, 27). The RAD
getic Particles (SEPs). Both GCRs and SEPs interact with the atmos- surface measurements provide a baseline for inferring the flux in these
phere and, if energetic enough, penetrate into the Martian soil, or more shielded environments (by validating and anchoring transport
regolith, where they produce secondary particles (including neutrons and models), and thus the foundation for understanding the limits to preserγ-rays) that contribute to the complex radiation environment on the Mar- vation of organic matter in the soil and rocks of Gale Crater.
tian surface, which is quite unlike that observed at the Earth’s surface.
GCRs are high energy particles (10 MeV/nuc to >10 GeV/nuc)
Results and Discussion
which are modulated by the heliosphere and anti-correlated with solar
The Curiosity rover landed successfully on Mars in Gale Crater at ~activity (18). The composition varies slightly depending on solar modu- 4.4 km MOLA (Mars Orbiter Laser Altimeter) altitude on 6 August
lation, with the proton abundance in the range 85-90%, helium ions ~10- 2012. On 7 August 2012, the RAD began taking observations of the
/ http://www.sciencemag.org/content/early/recent / 9 December 2013 / Page 1 / 10.1126/science.1244797
Downloaded from www.sciencemag.org on December 9, 2013
Mars’ Surface Radiation Environment
Measured with the Mars Science
Laboratory’s Curiosity Rover
2. radiation environment on Mars, incidentally 100 years to the day after
the discovery of cosmic rays on Earth by Victor Hess from a balloon in
Austria (31). The results reported here are time series of absorbed dose
rate, the average absorbed dose rate and average dose equivalent rate,
and LET spectra for ~300 Sols (1 Martian Sol = 24 hours 39 min.) from
Aug. 7, 2012 to June 1, 2013.
Figure 1 shows the radiation dose rate measured by RAD on the Mars
surface during the first 300 Sols on Mars, near the maximum of Solar
Cycle 24. The GCR dose rate can be seen to vary between 180 and 225
μGy/day, owing to the combined effects of: diurnal variations from atmospheric pressure changes, Mars seasonal variations at Gale Crater and
heliospheric structure variability due to solar activity and rotation.
The diurnal dose rates vary by a few percent due to diurnal change in
the Mars atmospheric column between Sols 290-302 (Fig. 2A). This
diurnal variation of the total atmospheric column mass is related to the
daily thermal tides that Mars experiences each Sol, whereby the direct
heating of the Martian atmosphere by the Sun produces global scale
waves that redistribute atmospheric mass (33). Comparison of the RAD
dose rate to the Rover Environment Monitoring Station (REMS) (34)
atmospheric pressure measurements shows there is an anti-correlation
between total dose rate and atmospheric pressure (Fig. 2B), which in
turn is directly related to column depth.
On the Mars surface, during the 300-day period near the maximum
of solar cycle 24, we find an average total GCR dose rate at Gale Crater
(-4.4 km MOLA) of 0.210 +/− 0.040 mGy/day, compared to 0.48 +/−
0.08 mGy/day measured during cruise inside the MSL spacecraft (Fig. 3
and Table 1). The difference in dose rate is driven by several influences:
First, the shielding of the lower hemisphere provided by the planet reduces the dose rate by a factor of ~2. Second, further deviations from
this factor of 2 are due to interactions of primary GCRs with the nucleons in the atmosphere (and soil). Additionally, the effective atmospheric
shielding is thicker than the spacecraft shielding of the instrument during
cruise. The dose rate is also influenced by the modulation of the GCR
flux by the sun, i.e., a stronger solar modulation results in overall lower
GCR fluxes and thus lower dose rates. The solar modulation parameter
during the surface mission to date has been ~577 MV, whereas the average Φ during cruise was ~635 MV (resulting in lower effective GCR
flux).
We find the average Quality Factor <Q> on the Martian surface to
be 3.05 +/− 0.3, compared with 3.82 +/− 0.3 measured during cruise.
This smaller <Q> is due to the thicker shielding in the field of view
(FOV) on the surface, because during cruise, approximately half of the
RAD FOV was lightly shielded (< 10 g cm−2) (35). The column depth of
the Martian atmosphere averaged about 21 g cm−2 over the first 300 sols
of Curiosity’s mission. Combining the tissue dose rate measurement
with <Q> yields an average GCR dose equivalent rate on the Mars surface of 0.64 ± 0.12 mSv/day (Fig. 4).
The SEP dose was obtained by subtracting the average GCR dose
rate for the duration of the SEP event. It is found to be 50 μGy in the
less-shielded of the two detectors used for dosimetry. Because the composition of SEP events (observed both on the surface and during cruise)
are dominantly protons, for which <Q> = ~1, the dose equivalent from
this event was about 50 μSv, approximately equal to 25% of the GCR
dose equivalent for the one day duration of the event.
The frequency and intensity of SEP events is highly variable and still
unpredictable, and although these observations were made near solar
maximum, this current solar activity cycle is very weak by historical
norms (36). Substantial/ Notable SEP events throughout recent history
(February 1956, August 1972, September 1989, etc.) have been reported
and modeled to be several orders of magnitude more intense than those
currently observed to date by the RAD (37).
Implications for Future Human Missions to Mars
Combining our measurements with those obtained during the cruise
phase (22), we estimate a Total Mission dose equivalent of ~1.01 Sv for
a round trip Mars surface mission with 180 days (each way) cruise, and
500 days on the Martian surface for this current solar cycle (Table 2).
These mission phase durations are based on one possible NASA Design
Reference Mission (38); many mission designs and many mission windows at different times in the solar cycle or a different solar cycle would
result in somewhat different radiation exposures. Because GCR flux is
modulated by solar activity (decreasing during solar activity maximum
and increasing during solar activity minimum) and the risk for exposure
to SEPs increases with solar activity, the contribution of each to the total
mission dose of a future Mars mission depends on when in the solar
cycle the mission occurs (3–6).
Estimates of Subsurface Dose Rates
The dose and dose equivalent rates reported in Tables 1 and 2 can be
extrapolated to obtain rates below the Martian surface, using the surface
measurements to anchor model predictions. Refining estimates of the
subsurface radiation environment is important because in-situ regolithbased materials are prime candidates for astronaut shelter shielding materials to reduce or mitigate the biological hazards associated with radiation exposures on future long duration human missions. These improved
subsurface radiation estimates give insight into the potential for the
preservation of possible organic biosignatures as a function of depth as
well as survival times of possible microbial or bacterial life forms left
dormant beneath the surface.
Several studies have modeled the expected subsurface radiation regime (26, 39), but the dose values depended until now on the modeled
radiation environment on the surface. Dartnell et al. (26, 27) assumed an
absorbed dose of ~150 mGy/year at the Martian surface, whereas Pavlov
et al. (28, 29) assumed an absorbed dose of 50 ±5 mGy/year. The actual
absorbed dose measured by the RAD (76 mGy/yr at the surface) (Table
3) allows for more precise estimations of the subsurface dose. Differences may be due in part to differing assumptions in the models about
the level of solar modulation compared to the actual level during the
measurement period as well as the amount of atmospheric shielding
above the surface. Also, all of the above models must assume a rock, ice,
or soil density. Based on compositional and morphological observations
of the rocks at the John Klein site in Gale Crater (42), we estimate a rock
density of 2.8 g/cm3, which approximates the density of an iron-rich
mudstone or siltstone. Although our estimates of subsurface dose depend
strongly on the models we used, they are useful for comparison purposes. Also note that the natural background radioactivity on present-day
Mars is thought to be on the order of ~1 μGy/day (43), suggesting that
GCR radiation is no longer the dominant source of radiation below ~3
m. This also implies that the effectiveness of regolith-based shielding
materials no longer improves beyond a thickness of ~3 m.
Implications for Microbial Survival Times
Energetic particles ionize molecules along their tracks. The energy
deposited by ionization or excitation greatly exceeds that required to
break many molecular bonds, including those in DNA, other organic
molecules and water, thus ionizing radiation is extremely damaging to
biomolecules through both direct and indirect mechanisms. Thus, measurements of the surface and subsurface radiation environment are critical
for estimating the survival probability and survival times of possible
dormant life forms found in the Martian soil, regolith, rock, and ice. For
this, the dose rates can be used to calculate the time it would take for
different bacterial species to accumulate a lethal dose of radiation in
different subsurface depths (44).
Even the radioresistant organism D. radiodurans would, if dormant,
/ http://www.sciencemag.org/content/early/recent / 13 December 2013 / Page 2 / 10.1126/science.1244797
3. be eradicated in the top several meters in a timespan of a few million
years (28, 29). However, inferred recurring climate changes in the postNoachian era, due to variations in the planetary obliquity on time scales
of several hundred thousand to a few million years (45), could lead to
recurring periods of metabolic activity of these otherwise dormant life
forms. In this case, it is hypothesized that accumulated radiation damages could be repaired and the “survival clock” of such life forms could be
reset to zero for the next dormant phase (26, 28), which could in turn
lead to possible survival to present times. It has been (27) estimated that
a 2-m depth drill was necessary to access viable radioresistant cells that
may have gone through this reanimation step within 450,000 years. Applying the RAD dose results, we estimate that only a 1-m depth drill is
necessary to access the same viable radioresistant cells.
small organic salts and CO2 via Fenton reactions (61). On Mars, this
oxidation process is likely accelerated by the presence of iron mineral
catalysts. Further, ionizing radiation plays a key role in the formation of
oxychlorine compounds in the atmosphere (62) and ices (63), which
have been deposited in sediments (64–66) where they may have undergone radiolysis (52) causing eventual oxidation of any organics by the
resulting products.
Although the presence of Martian organic matter has not been confirmed via in situ observation, our RAD measurements suggest that the
most favorable conditions for finding evidence of organics on Mars is in
rocks or soils that have been more recently exposed (e.g., eroded canyon
walls or recent impact craters) and do not show signs of aqueous activity
following exhumation.
Implications for the Preservation of Environmental Records and Organic Biosignatures
Whether the bulk of the Martian atmosphere was lost prior to the
Noachian era (~3.7-4.0 Gy ago), as recent isotope ratio measurements by
Curiosity suggest (46), or toward the end of the Noachian era (39, 47–
49), it is thought that the Martian surface has had little protection from
energetic particles for most of its history (50). Over such geologic time
scales, an enormous fluence of high energy charged particles (both primary and secondary) has interacted with, and most likely altered, the
Martian regolith, contributing substantially to the unique chemistry of
the Martian soil and rocks (51, 52), and affecting the preservation of
environmental records. The assessments of habitability and potential
biosignatures of any ancient environment depend on the robustness of
the preserved record, and ionizing radiation strongly influences chemical
compositions and structures, especially for water, salts, and redoxsensitive components such as organic matter (53–56). Carbon isotopic
compositions may also be altered in the upper 50 cm of rock and soil
(28). Organic molecules hold high potential for recording biosignatures
(57), and organic matter (biogenic or abiogenic) may provide a source of
carbon for habitable environments (42). Our RAD surface measurements
and subsurface estimates constrain the preservation window for Martian
organic matter following exhumation and exposure to ionizing radiation
in the top few meters of the Martian surface. Prior studies focused on the
top few centimeters of rock, such as that accessible by the MSL drill.
Using the amino acid degradation rates observed by (58), Pavlov et al.
(29) modeled a ~1000-fold decrease in 100 amu molecules in ~1 billion
years at 4-5 cm depth. The higher dose rate to rocks determined by RAD
reduces this period to ~650 million years. They postulated that higher
mass molecules would degrade much faster, assuming a molecular
chemistry comparable to amino acids. While this assumption is suitable
for biomolecules (proteins) of endolithic organisms, it is not representative of Martian biomolecules that survive early diagenesis in sediments,
geological organic matter in basalts (59), or exogenously delivered organics (60). Degradation rates for molecules of other organic chemistry
are not reported, but survival of organic matter in carbonaceous chondrites demonstrates that meteoritic organic matter survives ionizing radiation for billions of years.
Regardless of the source of Martian organic matter (meteoritic, geological, or biological), its bonds are susceptible to cleavage and radical
formation by ionizing charged particle radiation. Permanent bond scissions, subsequent cross-linking with other radicals, and volatile formation can occur. Radicals that are formed from cleaved bonds are
highly reactive and will react with inorganic and organic chemicals in
the immediate environment. In the presence of both radiation and reactive environmental chemicals, organic matter is highly susceptible to
alteration and eventual destruction. Irradiation of water and hydroxyl (OH) groups produces free radicals and molecules (H+, OH+, H2O2) that
will oxidize hydrocarbons and aromatic macromolecules to produce
Materials and Methods
The RAD instrument (67) consists of a combined charged and neutral particle detector, with a solid state detector telescope, CsI calorimeter, and plastic scintillator for neutron detection. Active coincidence
logic discriminates against charged particles entering the detector from
outside the charged particles telescope’s field of view, and anticoincidence logic enables detection of neutrons and γ-rays. The RAD
has a wide dynamic range for charged particles and is able to measure all
ion species that contribute to the radiation exposure on the surface of
Mars with a geometry factor of ~0.9 cm2 sr. The RAD measures differential fluxes of stopping charged particles with energies up to 95
MeV/nuc for protons and 4He, and up to 450 MeV/nuc for 56Fe. Neutral
particles are identified in the energy range from about 10 MeV to 100
MeV. The dE/dx resolution of the RAD is sufficient to distinguish between major particle species. The RAD measures dE/dx in silicon, but
these measurements can also be approximately related to Linear Energy
Transfer (LET) in water. The RAD dynamic range corresponds to the
LET range from 0.2 to ~1000 keV/μm in water.
Dose equivalent is determined by convoluting the Linear Energy
Transfer (LET) spectrum of the measured particles with a quality factor,
Q(L) (68), that is an approximate measure of biological effectiveness of
different radiation types. Dose is a purely physical quantity, with units of
Gray or milligray (1 Gray = 1 J/kg). Dose equivalent is dose weighted by
a dimensionless biological effectiveness factor which takes into account
the energy absorption characteristics of biological tissue, and is expressed in Sieverts or millisieverts.
Observations of SEP Event on 11 April 2013
Figure 5A shows the dose rate time series associated with the SEP
event enhancement seen on 11-12 April 2013 resulting from an M-class
flare on the Sun. Although the SEP event appeared relatively weak in
terms of flux increase as seen from Earth (GOES-13) (69), its energy
spectrum was hard enough to produce an enhancement of ~30% over the
GCR dose rate on the Martian surface. The 40-100 MeV proton flux
seen by STEREO-B (70) increased almost 4 orders of magnitude at the
peak of this event (Fig. 5B). Note that the minimum proton energy required to reach the surface in Gale Crater is about 150 MeV. STEREO-B
was leading Mars (in longitude) at the time of the event, and had similar,
but not identical, magnetic connection to the Sun. This event was the
first “hard spectrum” SEP event seen by RAD on the Mars surface. Because Mars was in solar conjunction at this time, GOES-13 was nearly
180 degrees in heliospheric longitude away, with fluxes of >50 and >100
MeV protons increasing by only two orders of magnitude (Fig. 5C). This
SEP event was very broad in heliospheric extent, expanding to greater
than 180 degrees in heliographic longitude from the Sun. (Interestingly,
this event was not observed by STEREO-A, which was trailing Mars at
the time.) These observations from the RAD provide an additional data
point to test models of the 3-D structure and propagation of SEPs
through the inner heliosphere.
/ http://www.sciencemag.org/content/early/recent / 13 December 2013 / Page 3 / 10.1126/science.1244797
4. References and Notes
1. M. H. Acuña, J. E. P. Connerney, P. Wasilewski, R. P. Lin, K. A. Anderson, C.
W. Carlson, J. McFadden, D. W. Curtis, D. Mitchell, H. Reme, C. Mazelle, J.
A. Sauvaud, C. d’Uston, A. Cros, J. L. Medale, S. J. Bauer, P. Cloutier, M.
Mayhew, D. Winterhalter, N. F. Ness, Magnetic Field and Plasma
Observations at Mars: Initial Results of the Mars Global Surveyor Mission.
Science 279, 1676–1680 (1998). doi:10.1126/science.279.5357.1676 Medline
2. Radiation Hazards to Crews on Interplanetary Missions. National Academy of
Sciences, Washington, DC, (1996).
3. L. C. Simonsen, J. E. Nealy, L. W. Townsend, J. W. Wilson, “Radiation
Exposure for Manned Mars Surface Missions,” NASA Technical Paper 2979
(1990).
4. L. C. Simonsen, J. E. Nealy, “Radiation Protection for Human Missions to the
Moon and Mars,” NASA Technical Paper 3079 (1991).
5. F. A. Cucinotta, W. Schimmerling, J. W. Wilson, L. E. Peterson, G. D.
Badhwar, P. B. Saganti, J. F. Dicello, Space radiation cancer risks and
uncertainties for Mars missions. Radiat. Res. 156, 682–688 (2001).
doi:10.1667/0033-7587(2001)156[0682:SRCRAU]2.0.CO;2 Medline
6. F. A. Cucinotta, M. Durante, Cancer risk from exposure to galactic cosmic
rays: implications for space exploration by human beings. Lancet Oncol. 7,
431–435 (2006). doi:10.1016/S1470-2045(06)70695-7 Medline
7. F. A. Cucinotta, M. H. Kim, L. J. Chappell, J. L. Huff, How safe is safe
enough? Radiation risk for a human mission to Mars. PLoS ONE 8, e74988
(2013). doi:10.1371/journal.pone.0074988 Medline
8. F. A. Cucinotta, L. Chappell, M. Y. Kim, “Space radiation cancer risk
projections and uncertainties–2012,” NASA Technical Paper 2013-217375
(2013).
9. S. P. McKenna-Lawlor, P. Gonçalves, A. Keating, G. Reitz, D. Matthiä,
Overview of energetic particle hazards during prospective manned missions to
Mars.
Planet.
Space
Sci.
63–64,
123–132
(2012).
doi:10.1016/j.pss.2011.06.017
10. L. C. Simonsen, J. E. Nealy, “Mars Surface Radiation Exposure for Solar
Maximum Conditions and 1989 Solar Proton Events,” NASA Technical Paper
3300 (1993).
11. F. A. Cucinotta, P. B. Saganti, J. W. Wilson, L. C. Simonsen, Model
predictions and visualization of the particle flux on the surface of Mars. J.
Radiat. Res. (Tokyo) 43, (Suppl), S35–S39 (2002). doi:10.1269/jrr.43.S35
Medline
12. G. De Angelis, M. S. Clowdsley, R. C. Singleterry, J. W. Wilson, A new Mars
radiation environment model with visualization. Adv. Space Res. 34, 1328–
1332 (2004). doi:10.1016/j.asr.2003.09.059 Medline
13. P. B. Saganti, F. A. Cucinotta, J. W. Wilson, L. C. Simonsen, C. Zeitlin,
Radiation Climate Map for Analyzing Risks to Astronauts on the Mars
Surface from Galactic Cosmic Rays. Space Sci. Rev. 110, 143–156 (2004).
doi:10.1023/B:SPAC.0000021010.20082.1a
14. F. A. Cucinotta, M. H. Kim, S. I. Schneider, D. M. Hassler, Description of
light ion production cross sections and fluxes on the Mars surface using the
QMSFRG model. Radiat. Environ. Biophys. 46, 101–106 (2007).
doi:10.1007/s00411-007-0099-y Medline
15. M. Y. Kim, M. L. Hayat, A. H. Feiveson, F. A. Cucinotta, Using high-energy
proton fluence to improve risk Prediction for consequences of solar particle
events. Adv. Space Res. 44, 1428–1432 (2009). doi:10.1016/j.asr.2009.07.028
16. T. C. Slaba, S. R. Blattnig, S. K. Aghara, L. W. Townsend, T. Handler, T. A.
Gabriel, L. S. Pinsky, B. Reddell, Coupled Neutron Transport for HZETRN.
Radiat. Meas. 45, 173–182 (2010). doi:10.1016/j.radmeas.2010.01.005
17. F. A. Cucinotta, L. J. Chappell, Updates to astronaut radiation limits: radiation
risks for never-smokers. Radiat. Res. 176, 102–114 (2011).
doi:10.1667/RR2540.1 Medline
18. L. J. Gleeson, W. I. Axford, Solar Modulation of Galactic Cosmic Rays.
Astrophys. J. 154, 1011 (1968). doi:10.1086/149822
19. J. A. Simpson, Elemental and Isotopic Composition of the Galactic Cosmic
Rays. Ann. Rev. Nuclear Part. Sci. 33, 323–382 (1983).
doi:10.1146/annurev.ns.33.120183.001543
20. P. O’Neill, Badhwar-O’Neill 2010 galactic cosmic ray flux model – revised.
IEEE Trans. Nucl. Sci. 57, 3148–3153 (2010).
21. H. V. Cane, I. G. Richardson, T. T. vonRosenvinge, M. Maksimovic, K.
Issautier, N. Meyer-Vernet, M. Moncuquet, F. Pantellini, The Properties of
Cycle 23 Solar Energetic Proton Events. AIP Conf. Proc. 1216, 687–690
(2010). doi:10.1063/1.3395960
22. C. Zeitlin, D. M. Hassler, F. A. Cucinotta, B. Ehresmann, R. F. WimmerSchweingruber, D. E. Brinza, S. Kang, G. Weigle, S. Böttcher, E. Böhm, S.
Burmeister, J. Guo, J. Köhler, C. Martin, A. Posner, S. Rafkin, G. Reitz,
Measurements of energetic particle radiation in transit to Mars on the Mars
Science
Laboratory.
Science
340,
1080–1084
(2013).
doi:10.1126/science.1235989 Medline
23. N. R. Pace, The universal nature of biochemistry. Proc. Natl. Acad. Sci.
U.S.A. 98, 805–808 (2001). doi:10.1073/pnas.98.3.805 Medline
24. D. Grinspoon, Lonely Planets: The Natural Philosophy of Alien Life,
HarperCollins (2003).
25. L. R. Dartnell, Ionizing radiation and life. Astrobiology 11, 551–582 (2011)
Astrobiology. doi:10.1089/ast.2010.0528 Medline
26. L. Dartnell, L. Desorgher, J. Ward, A. Coates, Modelling the surface and
subsurface martian radiation environment: implications for astrobiology.
Geophys. Res. Lett. 34, L02207 (2007a). doi:10.1029/2006GL027494
27. L. R. Dartnell, L. Desorgher, J. M. Ward, A. J. Coates, Martian sub-surface
ionising radiation: biosignatures and geology. Biogeosciences 4, 545–558
(2007b). doi:10.5194/bg-4-545-2007
28. A. K. Pavlov, A. V. Blinov, A. N. Konstantinov, 2002, ‘Sterilization of
Martian surface by cosmic radiation’. Planet. Space Sci. 50, 669–673 (2002).
doi:10.1016/S0032-0633(01)00113-1
29. A. K. Pavlov, G. Vasilyev, V. M. Ostryakov, A. K. Pavlov, P. Mahaffy,
Degradation of the organic molecules in the shallow subsurface of Mars due
to irradiation by cosmic rays. Geophys. Res. Lett. 39, L13202 (2012).
doi:10.1029/2012GL052166
30. S. I. Schneider, J. F. Kasting, Radiation Environments on Mars and their
Implications for Terrestrial Planetary Habitability, Bioastronomy 2007:
Molecules, Microbes and Extraterrestrial Life, ASP Conf. Series, vol. 420,
(2009).
31. V. F. Hess, Über Beobachtungen der durchdringenden Strahlung bei sieben
Freiballonfahrten. Phys. Z. 13, 1084–1091 (1912).
32. H. V. Cane, Coronal mass ejections and Forbush decreases. Space Sci. Rev.
93, 55–77 (2000). doi:10.1023/A:1026532125747
33. J. T. Schofield, J. R. Barnes, D. Crisp, R. M. Haberle, S. Larsen, J. A.
Magalhães, J. R. Murphy, A. Seiff, G. Wilson, The Mars Pathfinder
atmospheric structure investigation/meteorology (ASI/MET) experiment.
Science 278, 1752–1758 (1997). doi:10.1126/science.278.5344.1752 Medline
34. J. Gómez-Elvira, C. Armiens, L. Castañer, M. Domínguez, M. Genzer, F.
Gómez, R. Haberle, A.-M. Harri, V. Jiménez, H. Kahanpää, L. Kowalski, A.
Lepinette, J. Martín, J. Martínez-Frías, I. McEwan, L. Mora, J. Moreno, S.
Navarro, M. A. Pablo, V. Peinado, A. Peña, J. Polkko, M. Ramos, N. O.
Renno, J. Ricart, M. Richardson, J. Rodríguez-Manfredi, J. Romeral, E.
Sebastián, J. Serrano, M. Torre Juárez, J. Torres, F. Torrero, R. Urquí, L.
Vázquez, T. Velasco, J. Verdasca, M.-P. Zorzano, J. Martín-Torres, REMS:
The Environmental Sensor Suite for the Mars Science laboratory Rover.
Space Sci. Rev. 170, 583–640 (2012). doi:10.1007/s11214-012-9921-1
35. The larger relative uncertainty in <Q> measured on the surface compared to
that in cruise is due to increased uncertainty in the subtraction of the
background dose rate coming from Curiosity’s radioisotope thermoelectric
generator.
36. Y. Kamide, K. Kusano, Is Something Wrong With the Present Solar
Maximum? Space Weather 11, 140–141 (2013). doi:10.1002/swe.20045
37. M.-H. Y. Kim, A. J. Tylka, W. F. Dietrich, F. A. Cucinotta, AGU Meeting,
San Francisco, (2012).
38. B. G. Drake, S. J. Hoffman, D. W. Beatty, Human Exploration of Mars
Design Reference Architecture 5.0, Aerospace Conference, 2010 IEEE, 1-24
(2010).
39. B. Ehresmann, The Martian Radiation Environment - Early Mars and Future
Measurements with the Radiation Assessment Detector, Ph.D. thesis,
Christian-Albrechts-University of Kiel (2012).
40. HZETRN is the high charge and energy (HZE) transport code developed at
NASA Langley Research Center. It computes numerical solutions of the
Boltzmann transport equation, accounting for ionization energy loss and
nuclear interactions.
41. J. W. Wilson et al., 'HZETRN: Description of a Free-Space Ion and Nuclear
Transport and Shielding Computer Program', NASA Technical Paper 3495,
NASA STI Program, Hampton, VA, 1995.
42. J. P. Grotzinger, J. Crisp, A. R. Vasavada, R. C. Anderson, C. J. Baker, R.
Barry, D. F. Blake, P. Conrad, K. S. Edgett, B. Ferdowski, R. Gellert, J. B.
/ http://www.sciencemag.org/content/early/recent / 13 December 2013 / Page 4 / 10.1126/science.1244797
5. Gilbert, M. Golombek, J. Gómez-Elvira, D. M. Hassler, L. Jandura, M.
Litvak, P. Mahaffy, J. Maki, M. Meyer, M. C. Malin, I. Mitrofanov, J. J.
Simmonds, D. Vaniman, R. V. Welch, R. C. Wiens; Mars Science Laboratory
Mission and Science Investigation, Mars Science Laboratory Mission and
Science Investigation. Space Sci. Rev. 170, 5–56 (2012). doi:10.1007/s11214012-9892-2
43. C. Mileikowsky, F. A. Cucinotta, J. W. Wilson, B. Gladman, G. Horneck, L.
Lindegren, J. Melosh, H. Rickman, M. Valtonen, J. Q. Zheng, Natural transfer
of viable microbes in space. Icarus 145, 391–427 (2000).
doi:10.1006/icar.1999.6317 Medline
44. Baumstark-Khan, and R. Facius, 2001. Life under Conditions of Ionizing
Radiation, in: Astrobiology: The Quest for the Conditions of Life, edited by:
Horneck, G. and Baumstark-Khan, C., 260–283, Springer Verlag (2001).
45. J. Laskar, B. Levrard, J. F. Mustard, Orbital forcing of the martian polar
layered deposits. Nature 419, 375–377 (2002). doi:10.1038/nature01066
Medline
46. C. R. Webster, P. R. Mahaffy, G. J. Flesch, P. B. Niles, J. H. Jones, L. A.
Leshin, S. K. Atreya, J. C. Stern, L. E. Christensen, T. Owen, H. Franz, R. O.
Pepin, A. Steele, C. Achilles, C. Agard, J. A. Alves Verdasca, R. Anderson,
R. Anderson, D. Archer, C. Armiens-Aparicio, R. Arvidson, E. Atlaskin, A.
Aubrey, B. Baker, M. Baker, T. Balic-Zunic, D. Baratoux, J. Baroukh, B.
Barraclough, K. Bean, L. Beegle, A. Behar, J. Bell, S. Bender, M. Benna, J.
Bentz, G. Berger, J. Berger, D. Berman, D. Bish, D. F. Blake, J. J. Blanco
Avalos, D. Blaney, J. Blank, H. Blau, L. Bleacher, E. Boehm, O. Botta, S.
Böttcher, T. Boucher, H. Bower, N. Boyd, B. Boynton, E. Breves, J. Bridges,
N. Bridges, W. Brinckerhoff, D. Brinza, T. Bristow, C. Brunet, A. Brunner,
W. Brunner, A. Buch, M. Bullock, S. Burmeister, M. Cabane, F. Calef, J.
Cameron, J. Campbell, B. Cantor, M. Caplinger, J. Caride Rodríguez, M.
Carmosino, I. Carrasco Blázquez, A. Charpentier, S. Chipera, D. Choi, B.
Clark, S. Clegg, T. Cleghorn, E. Cloutis, G. Cody, P. Coll, P. Conrad, D.
Coscia, A. Cousin, D. Cremers, J. Crisp, A. Cros, F. Cucinotta, C. d’Uston, S.
Davis, M. Day, M. de la Torre Juarez, L. DeFlores, D. DeLapp, J. DeMarines,
D. DesMarais, W. Dietrich, R. Dingler, C. Donny, B. Downs, D. Drake, G.
Dromart, A. Dupont, B. Duston, J. Dworkin, M. D. Dyar, L. Edgar, K. Edgett,
C. Edwards, L. Edwards, B. Ehlmann, B. Ehresmann, J. Eigenbrode, B.
Elliott, H. Elliott, R. Ewing, C. Fabre, A. Fairén, K. Farley, J. Farmer, C.
Fassett, L. Favot, D. Fay, F. Fedosov, J. Feldman, S. Feldman, M. Fisk, M.
Fitzgibbon, M. Floyd, L. Flückiger, O. Forni, A. Fraeman, R. Francis, P.
François, C. Freissinet, K. L. French, J. Frydenvang, A. Gaboriaud, M.
Gailhanou, J. Garvin, O. Gasnault, C. Geffroy, R. Gellert, M. Genzer, D.
Glavin, A. Godber, F. Goesmann, W. Goetz, D. Golovin, F. Gómez Gómez, J.
Gómez-Elvira, B. Gondet, S. Gordon, S. Gorevan, J. Grant, J. Griffes, D.
Grinspoon, J. Grotzinger, P. Guillemot, J. Guo, S. Gupta, S. Guzewich, R.
Haberle, D. Halleaux, B. Hallet, V. Hamilton, C. Hardgrove, D. Harker, D.
Harpold, A. M. Harri, K. Harshman, D. Hassler, H. Haukka, A. Hayes, K.
Herkenhoff, P. Herrera, S. Hettrich, E. Heydari, V. Hipkin, T. Hoehler, J.
Hollingsworth, J. Hudgins, W. Huntress, J. Hurowitz, S. Hviid, K. Iagnemma,
S. Indyk, G. Israël, R. Jackson, S. Jacob, B. Jakosky, E. Jensen, J. K. Jensen,
J. Johnson, M. Johnson, S. Johnstone, A. Jones, J. Joseph, I. Jun, L. Kah, H.
Kahanpää, M. Kahre, N. Karpushkina, W. Kasprzak, J. Kauhanen, L. Keely,
O. Kemppinen, D. Keymeulen, M. H. Kim, K. Kinch, P. King, L. Kirkland,
G. Kocurek, A. Koefoed, J. Köhler, O. Kortmann, A. Kozyrev, J. Krezoski, D.
Krysak, R. Kuzmin, J. L. Lacour, V. Lafaille, Y. Langevin, N. Lanza, J.
Lasue, S. Le Mouélic, E. M. Lee, Q. M. Lee, D. Lees, M. Lefavor, M.
Lemmon, A. Lepinette Malvitte, R. Léveillé, É. Lewin-Carpintier, K. Lewis,
S. Li, L. Lipkaman, C. Little, M. Litvak, E. Lorigny, G. Lugmair, A.
Lundberg, E. Lyness, M. Madsen, J. Maki, A. Malakhov, C. Malespin, M.
Malin, N. Mangold, G. Manhes, H. Manning, G. Marchand, M. Marín
Jiménez, C. Martín García, D. Martin, M. Martin, J. Martínez-Frías, J. MartínSoler, F. J. Martín-Torres, P. Mauchien, S. Maurice, A. McAdam, E.
McCartney, T. McConnochie, E. McCullough, I. McEwan, C. McKay, S.
McLennan, S. McNair, N. Melikechi, P. Y. Meslin, M. Meyer, A.
Mezzacappa, H. Miller, K. Miller, R. Milliken, D. Ming, M. Minitti, M.
Mischna, I. Mitrofanov, J. Moersch, M. Mokrousov, A. Molina Jurado, J.
Moores, L. Mora-Sotomayor, J. M. Morookian, R. Morris, S. Morrison, R.
Mueller-Mellin, J. P. Muller, G. Muñoz Caro, M. Nachon, S. Navarro López,
R. Navarro-González, K. Nealson, A. Nefian, T. Nelson, M. Newcombe, C.
Newman, H. Newsom, S. Nikiforov, B. Nixon, E. Noe Dobrea, T. Nolan, D.
Oehler, A. Ollila, T. Olson, M. Á. de Pablo Hernández, A. Paillet, E. Pallier,
M. Palucis, T. Parker, Y. Parot, K. Patel, M. Paton, G. Paulsen, A. Pavlov, B.
Pavri, V. Peinado-González, L. Peret, R. Perez, G. Perrett, J. Peterson, C.
Pilorget, P. Pinet, J. Pla-García, I. Plante, F. Poitrasson, J. Polkko, R. Popa, L.
Posiolova, A. Posner, I. Pradler, B. Prats, V. Prokhorov, S. W. Purdy, E.
Raaen, L. Radziemski, S. Rafkin, M. Ramos, E. Rampe, F. Raulin, M. Ravine,
G. Reitz, N. Rennó, M. Rice, M. Richardson, F. Robert, K. Robertson, J. A.
Rodriguez Manfredi, J. J. Romeral-Planelló, S. Rowland, D. Rubin, M.
Saccoccio, A. Salamon, J. Sandoval, A. Sanin, S. A. Sans Fuentes, L. Saper,
P. Sarrazin, V. Sautter, H. Savijärvi, J. Schieber, M. Schmidt, W. Schmidt, D.
Scholes, M. Schoppers, S. Schröder, S. Schwenzer, E. Sebastian Martinez, A.
Sengstacken, R. Shterts, K. Siebach, T. Siili, J. Simmonds, J. B. Sirven, S.
Slavney, R. Sletten, M. Smith, P. Sobrón Sánchez, N. Spanovich, J. Spray, S.
Squyres, K. Stack, F. Stalport, T. Stein, N. Stewart, S. L. Stipp, K. Stoiber, E.
Stolper, B. Sucharski, R. Sullivan, R. Summons, D. Sumner, V. Sun, K.
Supulver, B. Sutter, C. Szopa, F. Tan, C. Tate, S. Teinturier, I. ten Kate, P.
Thomas, L. Thompson, R. Tokar, M. Toplis, J. Torres Redondo, M. Trainer,
A. Treiman, V. Tretyakov, R. Urqui-O’Callaghan, J. Van Beek, T. Van Beek,
S. VanBommel, D. Vaniman, A. Varenikov, A. Vasavada, P. Vasconcelos, E.
Vicenzi, A. Vostrukhin, M. Voytek, M. Wadhwa, J. Ward, E. Weigle, D.
Wellington, F. Westall, R. C. Wiens, M. B. Wilhelm, A. Williams, J.
Williams, R. Williams, R. B. Williams, M. Wilson, R. WimmerSchweingruber, M. Wolff, M. Wong, J. Wray, M. Wu, C. Yana, A. Yen, A.
Yingst, C. Zeitlin, R. Zimdar, M. P. Zorzano Mier; MSL Science Team,
Isotope ratios of H, C, and O in CO2 and H2O of the martian atmosphere.
Science 341, 260–263 (2013). doi:10.1126/science.1237961 Medline
47. B. Ehresmann, S. Burmeister, R.-F. Wimmer-Schweingruber, G. Reitz,
Influence of higher atmospheric pressure on the Martian radiation
environment: Implications for possible habitability in the Noachian epoch. J.
Geophys. Res. 116, 106 (2011). doi:10.1029/2011JA016616
48. R. Kahn, The evolution of CO2 on Mars. Icarus 62, 175–190 (1985).
doi:10.1016/0019-1035(85)90116-2
49. H. Lammer, W. Stumptner, G. J. Molina‐Cuberos, Martian atmospheric
evolution: Implications of an ancient intrinsic magnetic field, Astrobiology:
The Quest for the Conditions of Life, pp. 203–217, Springer, Berlin (2002).
50. B. M. Jakosky, R. J. Phillips, Mars’ volatile and climate history. Nature 412,
237–244 (2001). doi:10.1038/35084184 Medline
51. B. C. Clark, Geochemical components in Martian soil. Geochim. Cosmochim.
Acta 57, 4575–4581 (1993). doi:10.1016/0016-7037(93)90183-W
52. R. C. Quinn, H. F. Martucci, S. R. Miller, C. E. Bryson, F. J. Grunthaner, P. J.
Grunthaner, Perchlorate radiolysis on Mars and the origin of martian soil
reactivity. Astrobiology 13, 515–520 (2013). doi:10.1089/ast.2013.0999
Medline
53. R. W. Court, M. A. Sephton, J. Parnell, I. Gilmour, Raman spectroscopy of
irradiated organic matter. Geochim. Cosmochim. Acta 71, 2547–2568 (2007).
doi:10.1016/j.gca.2007.03.001
54. L. R. Dartnell, M. C. Storrie-Lombardi, C. W. Mullineaux, A. V. Ruban, G.
Wright, A. D. Griffiths, J. P. Muller, J. M. Ward, Degradation of
cyanobacterial biosignatures by ionizing radiation. Astrobiology 11, 997–1016
(2011). doi:10.1089/ast.2011.0663 Medline
55. L. R. Dartnell, K. Page, S. E. Jorge-Villar, G. Wright, T. Munshi, I. J.
Scowen, J. M. Ward, H. G. Edwards, Destruction of Raman biosignatures by
ionising radiation and the implications for life detection on Mars. Anal.
Bioanal. Chem. 403, 131–144 (2012). doi:10.1007/s00216-012-5829-6
Medline
56. P. A. Gerakines, R. L. Hudson, Glycine’s radiolytic destruction in ices: first in
situ laboratory measurements for Mars. Astrobiology 13, 647–655 (2013).
doi:10.1089/ast.2012.0943 Medline
57. R. E. Summons, J. P. Amend, D. Bish, R. Buick, G. D. Cody, D. J. Des
Marais, G. Dromart, J. L. Eigenbrode, A. H. Knoll, D. Y. Sumner,
Preservation of martian organic and environmental records: final report of the
Mars biosignature working group. Astrobiology 11, 157–181 (2011).
doi:10.1089/ast.2010.0506 Medline
58. G. Kminek, J. Bada, The effect of ionizing radiation on the preservation of
amino acids on Mars. Earth Planet. Sci. Lett. 245, 1–5 (2006).
doi:10.1016/j.epsl.2006.03.008
59. A. Steele, F. M. McCubbin, M. Fries, L. Kater, N. Z. Boctor, M. L. Fogel, P.
G. Conrad, M. Glamoclija, M. Spencer, A. L. Morrow, M. R. Hammond, R.
N. Zare, E. P. Vicenzi, S. Siljeström, R. Bowden, C. D. Herd, B. O. Mysen, S.
B. Shirey, H. E. Amundsen, A. H. Treiman, E. S. Bullock, A. J. Jull, A
/ http://www.sciencemag.org/content/early/recent / 13 December 2013 / Page 5 / 10.1126/science.1244797
6. reduced organic carbon component in martian basalts. Science 337, 212–215
(2012). doi:10.1126/science.1220715 Medline
60. S. Pizzarello, G. W. Cooper, G. J. Flynn, in Meteorites and the Early Solar
System D. S. Lauretta, H. Y. McSween Jr., Eds. (Arizona Press, Tucson, AZ,
2006), pp. 625–651.
61. S. A. Benner, K. G. Devine, L. N. Matveeva, D. H. Powell, The missing
organic molecules on Mars. Proc. Natl. Acad. Sci. U.S.A. 97, 2425–2430
(2000). doi:10.1073/pnas.040539497 Medline
62. D. C. Catling, M. W. Claire, K. J. Zahnle, R. C. Quinn, B. C. Clark, M. H.
Hecht, S. Kounaves, Atmospheric origins of perchlorate on Mars and in the
Atacama. J. Geophys. Res. 115, E00E11 (2010). doi:10.1029/2009JE003425
63. M. H. Hecht, S. P. Kounaves, R. C. Quinn, S. J. West, S. M. Young, D. W.
Ming, D. C. Catling, B. C. Clark, W. V. Boynton, J. Hoffman, L. P. Deflores,
K. Gospodinova, J. Kapit, P. H. Smith, Detection of perchlorate and the
soluble chemistry of martian soil at the Phoenix lander site. Science 325, 64–
67 (2009). Medline
64. Y. S. Kim, K. P. Wo, S. Maity, S. K. Atreya, R. I. Kaiser, Radiation-Induced
Formation of Chlorine Oxides and Their Potential Role in the Origin of
Martian Perchlorates. J. Am. Chem. Soc. 135, 4910–4913 (2013).
doi:10.1021/ja3122922 Medline
65. D. P. Glavin, C. Freissinet, K. E. Miller, J. L. Eigenbrode, A. E. Brunner, A.
Buch, B. Sutter, P. D. Archer, Jr., S. K. Atreya, W. B. Brinckerhoff, M.
Cabane, P. Coll, P. G. Conrad, D. Coscia, J. P. Dworkin, H. B. Franz, J. P.
Grotzinger, L. A. Leshin, M. G. Martin, C. McKay, D. W. Ming, R. NavarroGonzález, A. Pavlov, A. Steele, R. E. Summons, C. Szopa, S. Teinturier, P. R.
Mahaffy, Evidence for perchlorates and the origin of chlorinated
hydrocarbons detected by SAM at the Rocknest aeolian deposit in Gale
Crater. J. Geophys. Res. Planets 118, 1955 (2013). doi:10.1002/jgre.20144
66. L. A. Leshin, P. R. Mahaffy, C. R. Webster, M. Cabane, P. Coll, P. G.
Conrad, P. D. Archer, Jr., S. K. Atreya, A. E. Brunner, A. Buch, J. L.
Eigenbrode, G. J. Flesch, H. B. Franz, C. Freissinet, D. P. Glavin, A. C.
McAdam, K. E. Miller, D. W. Ming, R. V. Morris, R. Navarro-González, P.
B. Niles, T. Owen, R. O. Pepin, S. Squyres, A. Steele, J. C. Stern, R. E.
Summons, D. Y. Sumner, B. Sutter, C. Szopa, S. Teinturier, M. G. Trainer, J.
J. Wray, J. P. Grotzinger, O. Kemppinen, N. Bridges, J. R. Johnson, M.
Minitti, D. Cremers, J. F. Bell, L. Edgar, J. Farmer, A. Godber, M. Wadhwa,
D. Wellington, I. McEwan, C. Newman, M. Richardson, A. Charpentier, L.
Peret, P. King, J. Blank, G. Weigle, M. Schmidt, S. Li, R. Milliken, K.
Robertson, V. Sun, M. Baker, C. Edwards, B. Ehlmann, K. Farley, J. Griffes,
H. Miller, M. Newcombe, C. Pilorget, M. Rice, K. Siebach, K. Stack, E.
Stolper, C. Brunet, V. Hipkin, R. Leveille, G. Marchand, P. S. Sanchez, L.
Favot, G. Cody, L. Fluckiger, D. Lees, A. Nefian, M. Martin, M. Gailhanou,
F. Westall, G. Israel, C. Agard, J. Baroukh, C. Donny, A. Gaboriaud, P.
Guillemot, V. Lafaille, E. Lorigny, A. Paillet, R. Perez, M. Saccoccio, C.
Yana, C. Armiens-Aparicio, J. C. Rodriguez, I. C. Blazquez, F. G. Gomez, J.
Gomez-Elvira, S. Hettrich, A. L. Malvitte, M. M. Jimenez, J. Martinez-Frias,
J. Martin-Soler, F. J. Martin-Torres, A. M. Jurado, L. Mora-Sotomayor, G. M.
Caro, S. N. Lopez, V. Peinado-Gonzalez, J. Pla-Garcia, J. A. R. Manfredi, J.
J. Romeral-Planello, S. A. S. Fuentes, E. S. Martinez, J. T. Redondo, R.
Urqui-O’Callaghan, M.-P. Z. Mier, S. Chipera, J.-L. Lacour, P. Mauchien, J.B. Sirven, H. Manning, A. Fairen, A. Hayes, J. Joseph, R. Sullivan, P.
Thomas, A. Dupont, A. Lundberg, N. Melikechi, A. Mezzacappa, J.
DeMarines, D. Grinspoon, G. Reitz, B. Prats, E. Atlaskin, M. Genzer, A.-M.
Harri, H. Haukka, H. Kahanpaa, J. Kauhanen, O. Kemppinen, M. Paton, J.
Polkko, W. Schmidt, T. Siili, C. Fabre, M. B. Wilhelm, F. Poitrasson, K.
Patel, S. Gorevan, S. Indyk, G. Paulsen, S. Gupta, D. Bish, J. Schieber, B.
Gondet, Y. Langevin, C. Geffroy, D. Baratoux, G. Berger, A. Cros, C.
d’Uston, O. Forni, O. Gasnault, J. Lasue, Q.-M. Lee, S. Maurice, P.-Y.
Meslin, E. Pallier, Y. Parot, P. Pinet, S. Schroder, M. Toplis, E. Lewin, W.
Brunner, E. Heydari, C. Achilles, D. Oehler, D. Coscia, G. Israel, G. Dromart,
F. Robert, V. Sautter, S. Le Mouelic, N. Mangold, M. Nachon, F. Stalport, P.
Francois, F. Raulin, J. Cameron, S. Clegg, A. Cousin, D. DeLapp, R. Dingler,
R. S. Jackson, S. Johnstone, N. Lanza, C. Little, T. Nelson, R. C. Wiens, R. B.
Williams, A. Jones, L. Kirkland, A. Treiman, B. Baker, B. Cantor, M.
Caplinger, S. Davis, B. Duston, K. Edgett, D. Fay, C. Hardgrove, D. Harker,
P. Herrera, E. Jensen, M. R. Kennedy, G. Krezoski, D. Krysak, L. Lipkaman,
M. Malin, E. McCartney, S. McNair, B. Nixon, L. Posiolova, M. Ravine, A.
Salamon, L. Saper, K. Stoiber, K. Supulver, J. Van Beek, T. Van Beek, R.
Zimdar, K. L. French, K. Iagnemma, F. Goesmann, W. Goetz, S. Hviid, M.
Johnson, M. Lefavor, E. Lyness, E. Breves, M. D. Dyar, C. Fassett, D. F.
Blake, T. Bristow, D. DesMarais, L. Edwards, R. Haberle, T. Hoehler, J.
Hollingsworth, M. Kahre, L. Keely, C. McKay, M. B. Wilhelm, L. Bleacher,
W. Brinckerhoff, D. Choi, J. P. Dworkin, M. Floyd, J. Garvin, D. Harpold, A.
Jones, D. K. Martin, A. Pavlov, E. Raaen, M. D. Smith, F. Tan, M. Meyer, A.
Posner, M. Voytek, R. C. Anderson, A. Aubrey, L. W. Beegle, A. Behar, D.
Blaney, D. Brinza, F. Calef, L. Christensen, J. A. Crisp, L. DeFlores, B.
Ehlmann, J. Feldman, S. Feldman, J. Hurowitz, I. Jun, D. Keymeulen, J.
Maki, M. Mischna, J. M. Morookian, T. Parker, B. Pavri, M. Schoppers, A.
Sengstacken, J. J. Simmonds, N. Spanovich, M. T. Juarez, A. R. Vasavada, A.
Yen, F. Cucinotta, J. H. Jones, E. Rampe, T. Nolan, M. Fisk, L. Radziemski,
B. Barraclough, S. Bender, D. Berman, E. N. Dobrea, R. Tokar, D. Vaniman,
R. M. E. Williams, A. Yingst, K. Lewis, T. Cleghorn, W. Huntress, G.
Manhes, J. Hudgins, T. Olson, N. Stewart, P. Sarrazin, J. Grant, E. Vicenzi, S.
A. Wilson, M. Bullock, B. Ehresmann, V. Hamilton, D. Hassler, J. Peterson,
S. Rafkin, C. Zeitlin, F. Fedosov, D. Golovin, N. Karpushkina, A. Kozyrev,
M. Litvak, A. Malakhov, I. Mitrofanov, M. Mokrousov, S. Nikiforov, V.
Prokhorov, A. Sanin, V. Tretyakov, A. Varenikov, A. Vostrukhin, R. Kuzmin,
B. Clark, M. Wolff, S. McLennan, O. Botta, D. Drake, K. Bean, M. Lemmon,
S. P. Schwenzer, R. B. Anderson, K. Herkenhoff, E. M. Lee, R. Sucharski, M.
A. P. Hernandez, J. J. B. Avalos, M. Ramos, M.-H. Kim, C. Malespin, I.
Plante, J.-P. Muller, R. Ewing, W. Boynton, R. Downs, M. Fitzgibbon, K.
Harshman, S. Morrison, W. Dietrich, O. Kortmann, M. Palucis, A. Williams,
G. Lugmair, M. A. Wilson, D. Rubin, B. Jakosky, T. Balic-Zunic, J.
Frydenvang, J. K. Jensen, K. Kinch, A. Koefoed, M. B. Madsen, S. L. S.
Stipp, N. Boyd, J. L. Campbell, R. Gellert, G. Perrett, I. Pradler, S.
VanBommel, S. Jacob, S. Rowland, E. Atlaskin, H. Savijarvi, E. Boehm, S.
Bottcher, S. Burmeister, J. Guo, J. Kohler, C. M. Garcia, R. Mueller-Mellin,
R. Wimmer-Schweingruber, J. C. Bridges, T. McConnochie, M. Benna, H.
Bower, H. Blau, T. Boucher, M. Carmosino, H. Elliott, D. Halleaux, N.
Renno, M. Wong, B. Elliott, J. Spray, L. Thompson, S. Gordon, H. Newsom,
A. Ollila, J. Williams, P. Vasconcelos, J. Bentz, K. Nealson, R. Popa, L. C.
Kah, J. Moersch, C. Tate, M. Day, G. Kocurek, B. Hallet, R. Sletten, R.
Francis, E. McCullough, E. Cloutis, I. L. ten Kate, R. Kuzmin, R. Arvidson,
A. Fraeman, D. Scholes, S. Slavney, T. Stein, J. Ward, J. Berger, J. E.
Moores, J. P. Grotzinger, MSL Science Team, Volatile, Isotope and Organic
Analysis of Martian Fines with the Mars Curiosity Rover. Science 341,
1238937 (2013). doi:10.1126/science.1238937
67. D. M. Hassler, C. Z. Zeitlin, R. F. Wimmer-Schweingruber, S. Bottcher, C.
Martin, J. Andrews, E. B¨ohm, D. Brinza, M. Bullock, S. Burmeister, B.
Ehresmann, M. Epperly, D. Grinspoon, J. K¨ohler, O. Kortmann, K. Neal, J.
Peterson, A. Posner, S. Rafkin, L. Seimetz, K. Smith, Y. Tyler, G. Weigle, G.
Reitz, F. Cucinotta, The Radiation Assessment Detector (RAD) Investigation.
Space Sci. Rev. 170, 503–558 (2012). doi:10.1007/s11214-012-9913-1
68. International Commission on Radiological Protection, ICRP Publication 60:
1990 Recommendations of the International Commission on Radiological
Protection. Ann. ICRP 21, 1 (1991). doi:10.1016/0146-6453(91)90009-6
69. T. Onsager, R. Grubb, J. Kunches, L. Matheson, D. Speich, R. W. Zwickl, H.
Sauer, Operational uses of the GOES energetic particle detectors. GOES-8
and Beyond. Proc. SPIE 2812, 281–290 (1996). doi:10.1117/12.254075
70. T. T. von Rosenvinge et al., Space Sci. Rev. 136, 391–435 (2008).
doi:10.1007/s11214-007-9300-5
Acknowledgments: This paper is dedicated to Dr. Michael J. Wargo at NASA
HQ, who passed away unexpectedly on August 4, 2013. Mike was Chief
Exploration Scientist in the Human Exploration and Operations Mission
Directorate (HEOMD), and an enthusiastic supporter of collaborative projects
between Science and Exploration. He was a strong supporter of RAD, and a
valuable member of both the science and exploration communities. He was a
good friend and a wonderful human being, and he will be greatly missed.
RAD is supported by NASA under JPL subcontract #1273039 to Southwest
Research Institute and in Germany by Deutsches Zentrum fur Luft- und
Raumfahrt (DLR) and DLR's Space Administration grant numbers
50QM0501 and 50 QM1201 to the Christian Albrechts University, Kiel. Part
of this research was carried out at the Jet Propulsion Laboratory, California
Institute of Technology, under a contact with the National Aeronautics and
Space Administration. We would like to extend sincere gratitude to Jeff
Simmonds and Joy Crisp at JPL, Gale Allen, Michael Meyer, Chris Moore,
Victoria Friedensen and Rich Williams at NASA HQ, and Heiner Witte at
DLR in Germany for their unwavering support of RAD over the years. The
/ http://www.sciencemag.org/content/early/recent / 13 December 2013 / Page 6 / 10.1126/science.1244797
7. authors would also like to thank the reviewers for their careful and thoughtful
comments and suggestions. The data used in this paper are archived in the
NASA Planetary Data System’s Planetary Plasma Interactions Node at the
University of California, Los Angeles. The archival volume includes the full
binary raw data files, detailed descriptions of the structures therein, and
higher-level data products in human-readable form. The PPI node is hosted at
the following URL: http://ppi.pds.nasa.gov/.
Supplementary Materials
www.sciencemag.org/content/science.1244797/DC1
Full Author List
16 August 2013; accepted 13 November 2013
Published online 9 December 2013
10.1126/science.1244797
/ http://www.sciencemag.org/content/early/recent / 13 December 2013 / Page 7 / 10.1126/science.1244797
8. Fig. 1. Time series of radiation dose rate measured by RAD
on the surface of Mars. During this time, RAD observed a
dose rate enhancement from one hard SEP event on Sol 242
(12-13 April 2013), and several Forbush decreases (32),
resulting from soft SEP event-related Interplanetary Coronal
Mass Ejections (ICMEs) on Sols 50, 97, 208, and 259.
(These ICMEs serve as magnetic shields against the GCR,
thus reducing the observed flux.) Occasional brief gaps can
also be seen, usually caused by RAD having been powered
off so that other activities could take place on the spacecraft
without interference.
Fig. 2. Comparison of RAD dose rate
vs time and atmospheric pressure. (A)
RAD daily dose rate vs time. (B)
Comparison of RAD dose rate to
REMS atmospheric pressure.
/ http://www.sciencemag.org/content/early/recent / 13 December 2013 / Page 8 / 10.1126/science.1244797
9. Fig. 3. Comparison of charged particle LET spectrum measured on the
Mars surface (red) to that measured during cruise inside the MSL
spacecraft (black) with variable shielding (22). The energy deposited in
silicon has been converted to LET in water.
Fig. 4. Comparison of the radiation dose equivalent for a 500
day surface stay to that from a 180 day transit to Mars (22), a
six month stay on the International Space Station (ISS), and
several earth-based sources of radiation. Dose is a purely
physical quantity, with units of Gray or milligray (1 Gray = 1
J/kg).
/ http://www.sciencemag.org/content/early/recent / 13 December 2013 / Page 9 / 10.1126/science.1244797
10. Fig. 5. (A) Dose rate enhancement from a solar energetic particle (SEP) event observed on the Martian surface by
RAD on Sol 242 (11-12 April 2013), while Mars was in solar conjunction. (B) the same SEP event seen from the
STEREO-B spacecraft, almost magnetically aligned with Mars, and (C) The same SEP event seen by the GOES-13
satellite in earth orbit, almost 180 degrees away in heliospheric longitude.
/ http://www.sciencemag.org/content/early/recent / 13 December 2013 / Page 10 / 10.1126/science.1244797
11. Table 1. Radiation Environment Measured by MSL/RAD (2012-13) (GCR only). Charged particle fluxes for both cruise
2
and surface were calculated using the single-ended geometric factor for a two-detector coincidence (0.90 cm sr). Fluence
2
rates were calculated using all hits above threshold in a single detector (B, with area 1.92 cm ). Solar modulation was, on
average, slightly stronger during the first 300 sols on the surface than during cruise.
RAD Measurement
Mars Surface
MSL Cruise
Units
Charged Particle Flux
(A * B)
0.64 ± 0.06
1.43 ± 0.03
cm−2 s−1 sr−1
Fluence Rate (B)
1.84 ± 0.34
3.87 ± 0.34
cm−2 s−1
Dose Rate (Tissue-like)
(E detector)
0.21 ± 0.04
0.48 ± 0.08
mGy/day
Avg. Quality Factor <Q>
3.05 ± 0.26
3.82 ± 0.30
(dimensionless)
Dose Equivalent Rate
0.64 ± 0.12
1.84 ± 0.30
mSv/day
Total Mission Dose Equivalent (NASA
Design Reference Mission, DRM)
320 ± 50
(500 days)
662 ± 108
(2x180 days)
mSv
Table 2. Mars Radiation Environment Summary during 2012-13 Solar Maximum (GCR & SEP). The GCR dose
rates are per day and the SEP doses are per event, showing a range from the sampling of 5 (medium-size) SEP events
observed during cruise and the 1 (small) event observed on the surface. Although the one SEP event observed on the
Martian surface was small, it is our only statistical sampling to date (see Materials and Methods).
GCR Dose Rate
(mGy/day)
SEP Dose
(mGy/event)
SEP Dose
Equivalent
(mSv/event)
0.464
1.84
1.2-19.5a
1.2-19.5
0.210
MSL Cruise
(Zeitlin et al. 2013)
(22)
Mars Surface
GCR Dose
Equiv. Rate
(mSv/day)
0.64
0.025b
0.025
Table 3. Mars Subsurface Radiation Estimates (scaled to RAD Surface Measurements). Both subsurface dose estimates and
dose equivalent rated were determined by scaling HZETRN model (40, 41) calculations to RAD surface measurement values (Table
2).
Depth below
Surface
Effective Shielding mass (g/cm2)
GCR Dose
Rate
(mGy/yr)
GCR Dose
Equiv. Rate
(mSv/yr)
Mars Surface
(RAD)
-10 cm
-1 m
-2 m
-3 m
0
76
232
28
280
560
840
96
36.4
8.7
1.8
295
81
15
2.9
/ http://www.sciencemag.org/content/early/recent / 13 December 2013 / Page 11 / 10.1126/science.1244797