Sleep N H, Meibom A, Fridriksson Th, Coleman R G, Bird D K
Department of Geophysics, Stanford University, Stanford, CA 94305, USA.
Proc Natl Acad Sci U S A. 2004 Aug 31;101(35):12818-23. doi: 10.1073/pnas.0405289101. Epub 2004 Aug 23.
Metamorphic hydration and oxidation of ultramafic rocks produces serpentinites, composed of serpentine group minerals and varying amounts of brucite, magnetite, and/or FeNi alloys. These minerals buffer metamorphic fluids to extremely reducing conditions that are capable of producing hydrogen gas. Awaruite, FeNi3, forms early in this process when the serpentinite minerals are Fe-rich. Olivine with the current mantle Fe/Mg ratio was oxidized during serpentinization after the Moon-forming impact. This process formed some of the ferric iron in the Earth's mantle. For the rest of Earth's history, serpentinites covered only a small fraction of the Earth's surface but were an important prebiotic and biotic environment. Extant methanogens react H2 with CO2 to form methane. This is a likely habitable environment on large silicate planets. The catalytic properties of FeNi3 allow complex organic compounds to form within serpentinite and, when mixed with atmospherically produced complex organic matter and waters that circulated through basalts, constitutes an attractive prebiotic substrate. Conversely, inorganic catalysis of methane by FeNi3 competes with nascent and extant life.
超镁铁质岩石的变质水合作用和氧化作用产生蛇纹岩，蛇纹岩由蛇纹石族矿物以及不同含量的水镁石、磁铁矿和/或铁镍合金组成。这些矿物将变质流体缓冲至能够产生氢气的极端还原条件。镍纹石（FeNi3）在这个过程早期形成，此时蛇纹岩矿物富含铁。在月球形成撞击后，具有当前地幔铁/镁比值的橄榄石在蛇纹石化过程中被氧化。这个过程形成了地球地幔中的一些三价铁。在地球历史的其余时间里，蛇纹岩仅覆盖了地球表面的一小部分，但却是一个重要的前生物和生物环境。现存的产甲烷菌将氢气与二氧化碳反应生成甲烷。这在大型硅酸盐行星上可能是一个宜居环境。FeNi3的催化特性使复杂有机化合物能够在蛇纹岩中形成，并且当与大气中产生的复杂有机物质以及通过玄武岩循环的水混合时，构成了一种有吸引力的前生物底物。相反，FeNi3对甲烷的无机催化与新生生命和现存生命相互竞争。
