火星沸石作为大气甲烷的来源
Martian zeolites as a source of atmospheric methane
摘要：
火星甲烷的起源仍然知之甚少。一个合理的解释是，甲烷可能是由玄武质地壳的热液蚀变或超镁铁岩的蛇纹石化产生的，产生氢并将地壳碳还原为甲烷。一旦形成，火星上的甲烷储存通常与隐藏的笼形水库的存在有关。在这里，我们认为属于沸石家族的菱沸石和斜发沸石可能在火星地下形成一个可信的甲烷储存库。由于存在许多火山地形，沸石预计将广泛分布在火星上，根据最乐观的估计，其全球等效层可能高达$\sim$ 1公里以上。如果菱沸石和斜发沸石中存在的火星甲烷直接来自地下的非生物来源，那么每年几毫米的局部层的不稳定可能足以解释目前的观测结果。从这些沸石中零星释放的甲烷要求它们在其演化过程中也保持与大气隔离。多年来的甲烷释放可能是由于几种机制，如影响，地震活动或侵蚀。如果火星上普遍存在从挖掘出的菱沸石和/或斜发沸石中释放出的甲烷，那么盖尔陨石坑周围这些沸石的存在可以解释火星科学实验室观察到的甲烷水平的变化。
英文摘要：
The origin of the martian methane is still poorly understood. A plausible explanation is that methane could have been produced either by hydrothermal alteration of basaltic crust or by serpentinization of ultramafic rocks producing hydrogen and reducing crustal carbon into methane. Once formed, methane storage on Mars is commonly associated with the presence of hidden clathrate reservoirs. Here, we alternatively suggest that chabazite and clinoptilolite, which belong to the family of zeolites, may form a plausible storage reservoir of methane in the martian subsurface. Because of the existence of many volcanic terrains, zeolites are expected to be widespread on Mars and their Global Equivalent Layer may range up to more than $\sim$1 km, according to the most optimistic estimates. If the martian methane present in chabazite and clinoptilolite is directly sourced from an abiotic source in the subsurface, the destabilization of a localized layer of a few millimeters per year may be sufficient to explain the current observations. The sporadic release of methane from these zeolites requires that they also remained isolated from the atmosphere during its evolution. The methane release over the ages could be due to several mechanisms such as impacts, seismic activity or erosion. If the methane outgassing from excavated chabazite and/or clinoptilolite prevails on Mars, then the presence of these zeolites around Gale Crater could explain the variation of methane level observed by Mars Science Laboratory.
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