2. 木星衛星系と土星衛星系の違いを説明したい
タイタン
イオ エウロパ ガニメデ カリスト
岩石 岩石 氷 氷 未分化
イオ∼ガニメデは互いに軌道共鳴にある
大きな衛星は
タイタンのみ
(全衛星質量の95%)
氷 未分化
dial ice-rock mixtures may display distinct
degrees of internal differentiation. Impact-
induced melting and/or intense tidal heating
of Ganymede, locked in orbital resonances
with the inner neighboring satellites Io and
Europa, may have triggered runaway differ-
entiation, but Callisto farther out from Jupiter
ries and gradual unmixing of ice and rock may
also play a role for incomplete differentiation
of icy satellites.
References and Notes
1. L. Iess et al., Science 327, 1367 (2010).
2. R. Jaumann et al., in Titan from Cassini-Huygens, R.H.
Brown, J.-P. Lebreton, J. Hunter Waite, Eds. (Springer,
New York, 2009), pp. 75–140.
Inside Titan. Global gravity field and sha
pletely separated within Titan’s deep inte
may contain a cold water-ammonia ocean
water ice below (gray) and a floating ice/c
images show that the extent of separation
density that is predominantly affected by
28. • カリストの形成時間(未分化問題)
必要条件:形成時間 >5 105yr [Barr & Canup, 2008]
△ 計算結果:形成時間 ∼105yr
議論 1. 衛星の形成時間について
gap 形成後も弱い物質流入(1/100)を仮定 [D Angelo et al., 2003]
○ 形成時間 >106yr の衛星がカリスト軌道付近に形成
○ 全体的な特徴(個数・位置)はガリレオ衛星と調和的
△ 物質流入のさせ方に結果が依存(より詳細な研究を!)
•タイタンの形成時間
計算結果:形成時間 >106yr
→ タイタンも未分化である可能性を示唆
○ 最新のタイタンの観測と調和的![Iess et al., 2010]
dial ice-rock mixtures may display distinct
degrees of internal differentiation. Impact-
induced melting and/or intense tidal heating
ries and gradual unmixing
also play a role for incom
of icy satellites.
Inside Titan. Glo
pletely separated
may contain a col
water ice below (g
images show that
density that is pre