Ceresの重力場と形状から推論した部分的に微分された内部
R S Park1, A S Konopliv1, B G Bills1
1Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California 91109, USA.
Nature
|August 4, 2016
まとめ
ドーン宇宙船は,小惑星セレスが水位平衡状態にあることを明らかにし,岩質な核と揮発性物質に富んだ殻を持つ部分的に微分化した内部を示しています. これはセレスが熱的に進化したことを示唆しているが,その大きさに比べると複雑な歴史がある.
科学分野:
- * 惑星科学
- * 小惑星科学
- * 地理学
背景:
- * 遠隔観測により,小惑星 (1) Ceresの密度と形状が推定されました.
- * 過去のモデルは,均質から完全に差別化されたインテリアまでありました.
- * 重要なパラメータが欠けていて,慣性の瞬間,内部のモデルが制限されています.
研究 の 目的:
- *セレスの重力の変化と慣性の瞬間を測定する.
- *セレスの内部構造のモデルを制限する.
- * セレスの熱と組成の進化を理解するために.
主な方法:
- * ドーン宇宙船を使って重力と形状を測定した.
- * 水位平衡と慣性の瞬間を決定するために分析したデータ.
- * 内部構造を2層モデルでモデル化した.
主要な成果:
- * セレスは,0.37の正規化された平均慣性モーメントで,水静的均衡状態にある.
- * セレスは部分的に微分化されています: 揮発性物質に富んだ外殻を持つ岩石の核心です.
- *重力シグナル抑制は静止補償を示し,深さでは低粘度層を示唆しています.
- *外殻の厚さは70〜190kmで,密度は揮発性物質と岩の混合を示しています.
結論:
- *セレスの内部は熱的に進化したが,その差異化はその大きさに期待されるよりも複雑である.
- * 低粘度層の存在は,組成的ではなく熱グラデントを示しています.
- * 発見は,氷が豊富な中型岩体に対する単純なモデルに挑戦します.
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