稲妻による窒素固定が減少したため,アーカイアンの生命に窒素危機が起きた可能性がある

R Navarro-González¹, C P McKay, D N Mvondo

¹Laboratorio de Química de Plasmas y Estudios Planetarios, Instituto de Ciencias Nucleares, Universidad Nacional Autónoma de México, Circuito Exterior, Ciudad Universitaria, México Distrito Federal 04510, Mexico. Navarro@nuclecu.unam.mx

Nature

|July 14, 2001

まとめ

稲妻による窒素固定は,二酸化炭素のレベルが低下するにつれて,初期の地球では著しく減少しました. この減少は,生物学的窒素固定の進化を刺激し,生命に必要な栄養素の需要を満たしたのかもしれない.

科学分野:

地質化学地質化学
バイオジオケミストリーバイオジオケミストリー
天体生物学アストロバイオロジー

背景:

窒素は生命にとって不可欠ですが,大気中のN2はほとんど利用できません.
主に雷によるアビオティック窒素固定が,初期の地球の窒素を供給した.
生物学的窒素固定への移行は十分に理解されていません.

研究の目的:

初期の地球の雷の条件をシミュレートし,窒素固定率を評価するために.
大気組成の変化が非生物的窒素固定に与える影響を調査する.
生物学的窒素固定の進化の潜在的なトリガーを探求する.

主な方法:

様々なハデア紀とアーケア紀の大気組成における雷の実験シミュレーション.
異なるCO2およびN2濃度下での酸化窒素生成の分析.
地質的な時間スケールにおける窒素固定速度のモデリング.

主要な成果:

稲妻による酸化窒素の生成は,大気中のCO2がアーカイアン時代に減少したため,二次減量しました.
アビオティック窒素供給の減少は,約22億年前まで続いた.
Gyr-2.2後,酸素やメタンが上昇し,代替アビオティック窒素源が導入された可能性が高い.

結論:

稲妻で固定された窒素の一時的な,しかし顕著な減少は,アーカイアンで起こった可能性があります.
この窒素"危機"は,生物学的窒素固定の発展を促したのかもしれない.
初期の地球の窒素循環を理解することは,生命の鍵となる栄養素の起源を解読する鍵です.

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