火星の核の上に液体シリケート層がある証拠
1Institute of Geochemistry and Petrology, ETH Zürich, Zurich, Switzerland. amir.khan@erdw.ethz.ch.
Nature
|October 25, 2023
まとめ
火星
科学分野:
- 惑星科学
- 地震学
- 地理学
背景:
- InSightミッションの地震データは 火星の核が純粋な鉄より ~27%軽いことを示しました
- 地震と地質学的モデルは,宇宙化学的に利用できるよりも多くの揮発性元素 (H,C,S) を示唆しています.
- 核の構成モデルと 惑星形成の制約の不一致
研究 の 目的:
- 地震データを用いて 火星の核の構成と構造を調査する
- 火星内部の地震学,地質学,宇宙化学モデルとの矛盾を調和させるため
- コアとマントルの境界と上層層の性質を決定する.
主な方法:
- InSightの地震記録から得られた複数のP波の分析.
- 液体鉄合金の熱弾性特性の第一原理計算
- コア-マントルの境界に敏感な微分体波の移動時間データ
主要な成果:
- 溶けたシリケート層の 層状のコア・マントルの境界の証拠
- カーネルの半径の減少 (1,675 ± 30 km) とカーネルの密度の増加 (6.65 ± 0.1 g/cm3).
- 溶融シリケート層の厚さ (150 ± 15 km) と密度 (4.05 ± 0.05 g/cm3)
- 核の組成:85~91%の鉄・ニッケル,9~15%の軽い元素 (S,C,O,H)
結論:
- 推論されたコアプロパティは,地球物理学的および宇宙化学的要件間の不一致を解決します.
- 溶融したシリケート層が 小さくて密度の高い核の上にあり それは地震データと一致しています
- 火星のマグマチズムの産物は,このシリケート層の化学的特性を明らかにします.
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