Abiotic Production of Methane in Terrestrial Planets
Abiotic Production of Methane in Terrestrial Planets
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DOI：
10.1089/ast.2012.0817
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发表时间：
2013-06-01
期刊：
影响因子：
4.2
通讯作者：
Escobar-Briones, Elva
中科院分区：
文献类型：
--
作者：
Guzman-Marmolejo, Andres;Segura, Antigona;Escobar-Briones, Elva
在地球上，甲烷主要由生命产生，有人提出，在某些条件下，在系外行星光谱中检测到的甲烷可以被认为是一种生物特征。在这里，我们估计有多少甲烷可能会产生在热液喷口系统的蛇纹化，其主要的地质来源，使用的主要反应的动力学特性的甲烷生产蛇纹化。蛇纹岩化的产氢量被计算为地壳中有效FeO的函数，给定电流扩展速率。二氧化碳是甲烷形成的限制性反应物，因为它在热液喷口系统中以水的形式高度贫化。我们估计，对于1和5 M圆以上的岩石行星，最大CH 4表面通量分别为6.8 x 10（8）和1.3 x 10（9）分子cm（-2）s（-1）。使用1-D的光化学模型，我们模拟大气体积混合比为0.03和0.1 CO2计算大气甲烷浓度的最大生产这种化合物的蛇纹石化。结果发现，1颗M圈以上行星的丰度分别为2.5和2.1 ppmv，5颗M圈以上行星的丰度分别为4.1和3.7 ppmv。因此，低浓度的甲烷可能是由蛇纹石化作用产生的。对于类太阳恒星周围的可居住行星，如果甲烷浓度大于10 ppmv，则可能意味着生命的存在。
On Earth, methane is produced mainly by life, and it has been proposed that, under certain conditions, methane detected in an exoplanetary spectrum may be considered a biosignature. Here, we estimate how much methane may be produced in hydrothermal vent systems by serpentinization, its main geological source, using the kinetic properties of the main reactions involved in methane production by serpentinization. Hydrogen production by serpentinization was calculated as a function of the available FeO in the crust, given the current spreading rates. Carbon dioxide is the limiting reactant for methane formation because it is highly depleted in aqueous form in hydrothermal vent systems. We estimated maximum CH4 surface fluxes of 6.8 x 10(8) and 1.3 x 10(9) molecules cm(-2) s(-1) for rocky planets with 1 and 5 M-circle plus, respectively. Using a 1-D photochemical model, we simulated atmospheres with volume mixing ratios of 0.03 and 0.1 CO2 to calculate atmospheric methane concentrations for the maximum production of this compound by serpentinization. The resulting abundances were 2.5 and 2.1 ppmv for 1 M-circle plus planets and 4.1 and 3.7ppmv for 5 M-circle plus planets. Therefore, low atmospheric concentrations of methane may be produced by serpentinization. For habitable planets around Sun-like stars with N-2-CO2 atmospheres, methane concentrations larger than 10 ppmv may indicate the presence of life.