1 UK Centre for Astrobiology, School of Physics and Astronomy, University of Edinburgh, Edinburgh, UK.
2 Aquatic Biogeochemistry Research Unit, Ecosystems and Environment Research Programme, Faculty of Biological and Environmental Sciences, University of Helsinki, Helsinki, Finland.
Astrobiology. 2019 Mar;19(3):284-299. doi: 10.1089/ast.2018.1870.
A major objective in the exploration of Mars is to test the hypothesis that the planet hosted life. Even in the absence of life, the mapping of habitable and uninhabitable environments is an essential task in developing a complete understanding of the geological and aqueous history of Mars and, as a consequence, understanding what factors caused Earth to take a different trajectory of biological potential. We carried out the aseptic collection of samples and comparison of the bacterial and archaeal communities associated with basaltic fumaroles and rocks of varying weathering states in Hawai'i to test four hypotheses concerning the diversity of life in these environments. Using high-throughput sequencing, we found that all these materials are inhabited by a low-diversity biota. Multivariate analyses of bacterial community data showed a clear separation between sites that have active fumaroles and other sites that comprised relict fumaroles, unaltered, and syn-emplacement basalts. Contrary to our hypothesis that high water flow environments, such as fumaroles with active mineral leaching, would be sites of high biological diversity, alpha diversity was lower in active fumaroles compared to relict or nonfumarolic sites, potentially due to high-temperature constraints on microbial diversity in fumarolic sites. A comparison of these data with communities inhabiting unaltered and weathered basaltic rocks in Idaho suggests that bacterial taxon composition of basaltic materials varies between sites, although the archaeal communities were similar in Hawai'i and Idaho. The taxa present in both sites suggest that most of them obtain organic carbon compounds from the atmosphere and from phototrophs and that some of them, including archaeal taxa, cycle fixed nitrogen. The low diversity shows that, on Earth, extreme basaltic terrains are environments on the edge of sustaining life with implications for the biological potential of similar environments on Mars and their exploration by robots and humans.
火星探索的主要目标之一是检验火星存在生命的假说。即使没有生命存在，对可居住和不可居住环境进行测绘也是全面了解火星地质和水历史的一项必要任务，因此也是了解是什么因素导致地球走上不同的生物潜力轨道的关键。我们进行了无菌样本采集，并对夏威夷玄武岩喷气孔和不同风化状态的岩石中与细菌和古菌群落进行了比较，以检验四个与这些环境中生命多样性相关的假说。通过高通量测序，我们发现所有这些物质都被低多样性生物群所占据。细菌群落数据的多元分析显示，活跃喷气孔与包含残余喷气孔、未风化和同沉淀玄武岩的其他地点之间存在明显的分离。与我们的假设相反，即高水流环境（如具有活跃矿物浸出的喷气孔）将是生物多样性高的地点，与残余或非喷气孔地点相比，活跃喷气孔中的 alpha 多样性较低，这可能是由于喷气孔地点的微生物多样性受到高温的限制。将这些数据与居住在爱达荷州未风化和风化玄武岩中的群落进行比较表明，尽管在爱达荷州和夏威夷的古菌群落相似，但玄武岩材料的细菌分类组成在不同地点存在差异。在两个地点都存在的分类群表明，它们中的大多数从大气和光自养生物中获得有机碳化合物，其中一些，包括古菌分类群，循环固定氮。低多样性表明，在地球上，极端玄武岩地形是维持生命的边缘环境，这对火星上类似环境的生物潜力及其机器人和人类的探索具有影响。
