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地球の原始的な大気に対する大きな影響の化学的影響
B Fegley1, R G Prinn, H Hartman
1Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, Cambridge 02139, USA.
Nature
|January 23, 1986
まとめ
初期の地球での巨大衝突は,生命の鍵となる分子を作り出したのかもしれない. この研究は,小惑星の衝突で有機合成の重要な前駆体である水素シアン化物 (HCN) とホルムアルデヒド (H2CO) がどのように生成されたかをモデル化しています.
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.
- 大気化学 大気化学
背景:
- 初期の地球は,小惑星や彗星による激しい爆撃を経験しました.
- この爆撃は,原始的な大気を大きく変えたのかもしれない.
- このような衝撃は,有機化合物の無生物合成に不可欠な前駆体分子を生成した可能性があります.
研究 の 目的:
- 地球の原始的な大気中の衝突条件下で,水素シアン化物 (HCN) とホルムアルデヒド (H2CO) の生成をモデル化する.
- 衝突で発生したHCNとH2COがプレバイオティック化学に与える潜在的貢献を評価する.
主な方法:
- 熱化学的均衡と化学的運動計算を活用した.
- 温度,圧力,および初期大気組成の範囲にわたる衝撃を受けた空気パセルのモデル化.
- 炭素と酸素 (C/O) の比率が1以上または1に等しい大気に集中しています.
主要な成果:
- ボリドの衝突は,C/O>=1大気に対して,重要なHCN体積混合比率 (衝突地域では10^-3から10^-5,地球規模では10^-5から10^-12) を生み出します.
- 衝撃地域におけるH2COの混合比率は10^-7から10^-9の範囲にあり,大気からの迅速な除去により,地球規模での分布は限られている.
- 海へのHCNの流れは,年間 (3-14) x 10^11 mol HCNを供給することができる.
結論:
- 初期の地球への影響は,前生物学的HCNの妥当な源であり,他の推定された源を潜在的に超えた.
- 生成されたHCNは,複雑な有機分子の無生物合成において重要な役割を果たした可能性がある.
- H2COが生成される一方で,その短い大気中の寿命は,地球上のプレバイオティック化学への貢献を制限する.
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