水の活動と初期の火星での生命への挑戦
Nicholas J Tosca1, Andrew H Knoll, Scott M McLennan
1Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA 02138, USA. ntosca@fas.harvard.edu
Science (New York, N.Y.)
|May 31, 2008
まとめ
古代の火星には酸性で塩分のある液体の水が存在していたが,その高い塩分度が,地球上の生命の限界を超えた可能性が高い. この研究では,火星の環境における水活動 (aH2O) を調査し,微生物の居住可能性にとって潜在的に過酷な条件を発見しました.
科学分野:
- 天体生物学 アストロバイオロジー
- 惑星科学は惑星科学である.
- 地質化学 地質化学
背景:
- インシット・ミッションと軌道探査では,古代の火星は酸性,塩性液体の水を持っていたことが明らかになった.
- この水の居住性は,塩分度量である水活動 (aH2O) に極めて依存しています.
- 陸上の生命は,水の活動に鋭く定義された限界を持っています.
研究 の 目的:
- 古代火星の表面水における最大水活性 (aH2O) を計算する.
- 塩分制約に基づいて,陸上の生物のためのこれらの水の居住性を評価する.
- 塩漬けから塩が降水したメリディアニ・プランウムのような環境を評価するために.
主な方法:
- 火星のデータから流体化学と塩分鉱物学の制約を活用した.
- 特定の火星環境における計算された最大水活動量 (aH2O).
- 計算されたaH2Oレベルを,陸上の生物の既知の許容限界と比較した.
主要な成果:
- 計算によると,文書化されている火星の水面の塩分量は,しばしば陸上の生命の許容レベルを超えていることが示されています.
- 塩水鉱物学と流体化学は,非常に低い水の活動を持つ条件を示唆しています.
- メリディアニ・プランウムのような環境は,おそらく高塩分状態を経験した.
結論:
- 古代の火星の表面水,特にメリディアン平原のような環境では,既知の地上の生命を支えるには塩分が多すぎた可能性が高い.
- これらの塩塩の熱力学的条件 (低aH2O) は,地球に似た地球外生命の可能性に挑戦しています.
- 火星での居住可能性の全範囲を理解するためにさらなる研究が必要です.
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