Harris Rachel L, Schuerger Andrew C
Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA, 02138, USA.
NASA Postdoctoral Management Program Fellow, Astrobiology Program, NASA Headquarters, Washington, DC, 20546, USA.
Sci Rep. 2025 Jan 22;15(1):2880. doi: 10.1038/s41598-025-86145-1.
Mars, with its ancient history of long-lived habitable environments, continues to captivate researchers exploring the potential for extant life. This study investigates the biosignature potential of Martian methane by assessing the viability of hydrogenotrophic methanogenesis in Methanosarcina barkeri MS under simulated Martian surface conditions. We expose M. barkeri to sustained hypobaria (7-12 mbar), low temperature (0˚C), and a CO-dominated gas mixture mimicking the Martian atmosphere. The results demonstrate statistically quantifiable CH production under all tested conditions, including at 7-12 mbar. Transcriptomics reveal that low total pressure and temperature did not significantly impact gene expression, highlighting the resilience of M. barkeri. However, atmospheric gas composition, specifically Mars gas with 2.9% pH, led to significant down-regulation of methanogenesis genes, hindering growth over 14 days. Notably, CH production scaled with the partial pressure of H, revealing that hydrogen uptake affinity is a stronger predictor of habitability and methanogenic potential than favorable Gibbs free energy of reaction. Our findings suggest that Mars' subsurface could harbor habitable refugia capable of supporting methanogenesis, sustaining microbial life at low metabolic steady states. These insights challenge assumptions about Martian habitability and have implications for astrobiological exploration, planetary protection, and in situ resource utilization for future human missions.
火星拥有长期适宜居住环境的古老历史，一直吸引着研究人员探索现存生命的可能性。本研究通过评估巴氏甲烷八叠球菌MS在模拟火星表面条件下氢营养型产甲烷作用的可行性，来研究火星甲烷的生物标志物潜力。我们将巴氏甲烷八叠球菌暴露于持续的低压（7 - 12毫巴）、低温（0˚C）以及模拟火星大气的以一氧化碳为主的气体混合物中。结果表明，在所有测试条件下，包括7 - 12毫巴时，都有可统计量化的甲烷产生。转录组学显示，低总压和低温对基因表达没有显著影响，突出了巴氏甲烷八叠球菌的适应能力。然而，大气气体成分，特别是含2.9%氢气的火星气体，导致产甲烷基因显著下调，阻碍了14天内的生长。值得注意的是，甲烷产生量与氢气分压成比例，这表明氢气摄取亲和力比有利的反应吉布斯自由能更能预测宜居性和产甲烷潜力。我们的研究结果表明，火星地下可能存在能够支持产甲烷作用的宜居避难所，在低代谢稳态下维持微生物生命。这些见解挑战了关于火星宜居性的假设，并对天体生物学探索、行星保护以及未来人类任务的原位资源利用具有启示意义。
