论文标题
继发火山气氛的生长和演变：ii。动力学的重要性
Growth and Evolution of Secondary Volcanic Atmospheres: II. The Importance of Kinetics
论文作者
论文摘要
火山主义是挥发性元素（例如C和H到地球大气层）的主要且长期的来源，可能是维纳斯大气层的大气层，可能是用于外部行星的。模拟大气的火山生长通常是两个假设之一：该大气形成是由火山主义的高温平衡设定的；或者，这种火山气体在热力学上重新校准了地表环境的新温度。在后一种情况下，已经提出火山气氛可能会产生生物签名的假阳性。在这里，我们通过执行化学动力学计算来测试这种推论的假设，以估计在简单的0D气氛中，忽略了光化学和反应催化的简单0D气氛中，火山来源的气氛的松弛时间尺度是热化学平衡的。我们证明，对于具有火山气氛的行星，只有在大气温度高于〜700K的情况下，才能假设在地质时间尺度上进行热化学平衡。在较低温度下缓慢的化学动力学抑制了对氧化还原敏感物种的放松对低温热化学平衡的放松，从而排除了仅通过热化学来产生两个独立的生物签名：1。氨和2。co $ _2 $和CH $ _4 $的共同发生的共同含量的共同使用，这是该co $ _2 $ $ _4 $ cos in the Inders in the Inders co. co n ofders in the Indersign the Indersign the Indersign the Indersign the Insuption in the Indersign the Insuption in the Indersign the Insuption in。 生活。如果被解释为在热化学平衡处，则在其脱气的高温下淬火，也具有从更氧化的地幔中产生的标准特征。因此，即使它们的气氛纯粹是起源于火山，这也使将气氛与岩石系外行星的内部联系起来变得复杂。
Volcanism is a major and long-term source of volatile elements such as C and H to Earth's atmosphere, likely has been to Venus's atmosphere, and may be for exoplanets. Models simulating volcanic growth of atmospheres often make one of two assumptions: either that atmospheric speciation is set by the high-temperature equilibrium of volcanism; or, that volcanic gases thermochemically re-equilibrate to the new, lower, temperature of the surface environment. In the latter case it has been suggested that volcanic atmospheres may create biosignature false positives. Here, we test the assumptions underlying such inferences by performing chemical kinetic calculations to estimate the relaxation timescale of volcanically-derived atmospheres to thermochemical equilibrium, in a simple 0D atmosphere neglecting photochemistry and reaction catalysis. We demonstrate that for planets with volcanic atmospheres, thermochemical equilibrium over geological timescales can only be assumed if the atmospheric temperature is above ~700K. Slow chemical kinetics at lower temperatures inhibit the relaxation of redox-sensitive species to low-temperature thermochemical equilibrium, precluding the production of two independent biosignatures through thermochemistry alone: 1. ammonia, and 2. the co-occurrence of CO$_2$ and CH$_4$ in an atmosphere in the absence of CO. This supports the use of both biosignatures for detecting life. Quenched at the high temperature of their degassing, volcanic gases also have speciations characteristic of those produced from a more oxidized mantle, if interpreted as being at thermochemical equilibrium. This therefore complicates linking atmospheres to the interiors of rocky exoplanets, even when their atmospheres are purely volcanic in origin.
