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arXiv 1610.09697astro-ph.EP
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火星早期温室效应的短暂减少

Transient reducing greenhouse warming on early Mars

Robin Wordsworth, Yulia Kalugina, Sergei Lokshtanov, Andrei Vigasin, Bethany Ehlmann, James Head, Cecilia Sanders, Huize Wang

摘要:

早期火星上存在大量液态水的证据是行星研究中一个长期存在的问题。在这里,我们提出了新的从头算光谱和逐线气候计算的变暖潜力减少早期火星大气。我们发现,CO2-H2和CO2-CH 4碰撞诱导吸收(CIA)的强度以前被大大低估。与之前的预期相反,甲烷在早期火星上可能是一种强大的温室气体,这是因为在250-500 cm^-1的光谱窗口区域内存在CO2-CH 4 CIA。在0.5 bar CO2或更高的大气中,H2或CH 4的百分比水平使年平均地面温度升高数十度,当压力为1.25-2 bar且H2和CH 4为2-10%时,温度达到273 K。火星地壳水蚀后产生的甲烷和氢可能与火山释放的二氧化碳结合,形成这种成分的短暂大气层4.5-3.5 Ga。我们的研究结果还表明,有人居住的系外行星可以在距离其宿主恒星相当远的地方保留表面液态水。

英文摘要:

The evidence for abundant liquid water on early Mars despite the faint young Sun is a long-standing problem in planetary research. Here we present new ab initio spectroscopic and line-by-line climate calculations of the warming potential of reduced atmospheres on early Mars. We show that the strength of both CO2-H2 and CO2-CH4 collision-induced absorption (CIA) has previously been significantly underestimated. Contrary to previous expectations, methane could have acted as a powerful greenhouse gas on early Mars due to CO2-CH4 CIA in the critical 250-500 cm^-1 spectral window region. In atmospheres of 0.5 bar CO2 or more, percent levels of H2 or CH4 raise annual mean surface temperatures by tens of degrees, with temperatures reaching 273 K for pressures of 1.25-2~bar and 2-10% of H2 and CH4. Methane and hydrogen produced following aqueous alteration of Mars' crust could have combined with volcanically outgassed CO2 to form transient atmospheres of this composition 4.5-3.5 Ga. Our results also suggest that inhabited exoplanets could retain surface liquid water at significant distances from their host stars.

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