誘導磁場は,EuropaとCallistoの地下海洋の証拠として使用されています
K K Khurana1, M G Kivelson, D J Stevenson
1Institute of Geophysics and Planetary Physics, University of California, Los Angeles 90095, USA. kkhurana@igpp.ucla.edu
Nature
|October 31, 1998
まとめ
ガリレオ宇宙船のデータによると,ヨーロッパとカリストは,地表の下にある塩の海を持っている可能性がある. 誘導磁場は,その表面の下にある電気伝導性層を示し,海洋仮説を支持する.
科学分野:
- 惑星科学は惑星科学である.
- マグネトヒドロダイナミクス
- 天体生物学 アストロバイオロジー
背景:
- ガリレオ宇宙船は木星を周回し,ガリレオの衛星を研究しています.
- 前回の磁気計のデータによると,ヨーロッパとカリストには大きな内部磁場がないと示唆されていた.
- 木星の内部磁気圏は,その衛星と相互作用するダイナミックなプラズマ環境を特徴としています.
研究 の 目的:
- ヨーロッパとカリストの近くの磁場乱れを調査する.
- これらの乱れを誘導磁場の証拠として解釈する.
- 地下電気伝導性と潜在的海洋への影響を評価する.
主な方法:
- ガリレオ宇宙船がヨーロッパとカリスタと接近した際の磁気計データを分析した.
- 月の中の電磁誘導のモデリング.
- 木星の磁気圏の文脈で観測された磁場乱れの解釈.
主要な成果:
- 木星の外部磁場がヨーロッパとカリストの近くで大きな波乱を観測した.
- これらの波動は,月内の渦流によって生成された誘導磁場と一致しています.
- 計算によると,両月の表面のすぐ下には,非常に電気伝導性の高い層があることが示されています.
結論:
- 導電性層は,塩分のある液体の水の海洋の存在によって最もよく説明されます.
- この発見は,EuropaとCallistoの地下海洋の存在を強く支持しています.
- この結果は,欧州の海洋に関する既存の間接的な地質学的証拠と一致しています.
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