1 Planetary Science Institute , Tucson, Arizona, USA.
2 Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma 2, Roma, Italy, and Faculty of Environmental Science and Engineering, Babes-Bolyai University , Cluj-Napoca, Romania .
Astrobiology. 2017 Dec;17(12):1233-1264. doi: 10.1089/ast.2017.1657. Epub 2017 Aug 3.
Methane on Mars is a topic of special interest because of its potential association with microbial life. The variable detections of methane by the Curiosity rover, orbiters, and terrestrial telescopes, coupled with methane's short lifetime in the martian atmosphere, may imply an active gas source in the planet's subsurface, with migration and surface emission processes similar to those known on Earth as "gas seepage." Here, we review the variety of subsurface processes that could result in methane seepage on Mars. Such methane could originate from abiotic chemical reactions, thermogenic alteration of abiotic or biotic organic matter, and ancient or extant microbial metabolism. These processes can occur over a wide range of temperatures, in both sedimentary and igneous rocks, and together they enhance the possibility that significant amounts of methane could have formed on early Mars. Methane seepage to the surface would occur preferentially along faults and fractures, through focused macro-seeps and/or diffuse microseepage exhalations. Our work highlights the types of features on Mars that could be associated with methane release, including mud-volcano-like mounds in Acidalia or Utopia; proposed ancient springs in Gusev Crater, Arabia Terra, and Valles Marineris; and rims of large impact craters. These could have been locations of past macro-seeps and may still emit methane today. Microseepage could occur through faults along the dichotomy or fractures such as those at Nili Fossae, Cerberus Fossae, the Argyre impact, and those produced in serpentinized rocks. Martian microseepage would be extremely difficult to detect remotely yet could constitute a significant gas source. We emphasize that the most definitive detection of methane seepage from different release candidates would be best provided by measurements performed in the ground or at the ground-atmosphere interface by landers or rovers and that the technology for such detection is currently available. Key Words: Mars-Methane-Seepage-Clathrate-Fischer-Tropsch-Serpentinization. Astrobiology 17, 1233-1264.
火星上的甲烷是一个特别引人关注的话题，因为它可能与微生物生命有关。好奇号火星车、轨道飞行器和地面望远镜对甲烷的可变探测，加上甲烷在火星大气中的短寿命，可能意味着火星地下存在一个活跃的气源，其迁移和表面排放过程类似于地球上已知的“气体渗漏”。在这里，我们回顾了可能导致火星甲烷渗漏的各种地下过程。这种甲烷可能源自非生物化学反应、非生物或生物有机质的热成因改变，以及古代或现存微生物代谢。这些过程可以在很宽的温度范围内发生，既存在于沉积岩中，也存在于火成岩中，它们共同增加了大量甲烷在早期火星上形成的可能性。甲烷沿断层和裂缝向地表渗漏，通过集中的宏观渗漏和/或弥散的微渗漏排放。我们的工作强调了火星上可能与甲烷释放有关的特征类型，包括 Acidalia 或 Utopia 中的泥火山状土丘；Gusev 陨石坑、Arabia Terra 和 Valles Marineris 中提出的古代泉水；以及大型撞击坑的边缘。这些地方可能曾经是宏观渗漏的地点，现在可能仍在排放甲烷。微渗漏可能通过二分体沿线的断层或裂缝发生，例如 Nili Fossae、Cerberus Fossae、Argyre 撞击和蛇纹石化岩石中产生的裂缝。火星微渗漏将极难远程探测到，但可能构成重要的气源。我们强调，从不同释放候选物中探测甲烷渗漏的最明确方法是由着陆器或火星车在地面或地面-大气界面进行的测量提供，并且目前已经有了用于这种探测的技术。关键词：火星-甲烷-渗漏-包合物-费歇尔-托普施-蛇纹石化。天体生物学 17，1233-1264。
