In most environments on Earth, habitable environments contain life. Experiments were conducted to investigate the decoupling of the presence of habitable conditions and life. A set of microcosms habitable for known groups of organisms, but uninhabited (i.e., uninhabited habitats), was exposed to external environmental conditions to test the hypothesis that extreme habitable environments can remain uninhabited for sustained time periods. These microcosms were made of tubes containing liquid water and inorganic N, P, and S. Organics (used as electron donors and as a C source) were provided as L and D amino acids. One set of uninhabited habitats contained no additional salts, one set contained saturated NaCl, and one set contained saturated MgSO₄. A ddH₂O control and a complex medium for Halobacterium were used as controls. The presence of organisms was tested by enumeration of colonists and sequencing of extracted DNA. At each time point, inoculation into fresh medium was used to test for growth of organisms. After 1 week, the “no salt” and saturated MgSO₄ solutions were colonized. After 6 months, both the NaCl-saturated and Halobacterium solutions remained uninhabited, but all other samples were colonized. These experiments demonstrate that certain types of habitable liquid water environments exposed to microbial atmospheric inoculation, even on Earth, can remain devoid of reproducing life for many months. On other planetary bodies, such as Mars, these data imply the possibility of preserved transient water bodies that would record habitable conditions, but no evidence of life, even if life existed elsewhere on the planet.

中文翻译：

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可居住但无人居住的水溶液的持久性及其在外星环境中的应用。

在地球上的大多数环境中，宜居环境包含生命。进行实验以研究居住条件与生活之间的脱钩。一组可居住在已知生物群中但无人居住（即无人居住的栖息地）的微观世界暴露于外部环境条件，以检验以下假设：极端可居住环境可以在持续的时间段内保持无人居住。这些缩影由装有液态水和无机N，P和S的试管制成。有机物（用作电子给体和C源）用作L和D氨基酸。一组无人居住的栖息地不包含其他盐分，一组包含饱和的NaCl，一组包含饱和的MgSO ₄。ddH ₂将O对照和用于盐杆菌的复合培养基用作对照。通过计数殖民者和对提取的DNA进行测序来测试生物的存在。在每个时间点，接种到新鲜培养基中以测试生物的生长。1周后，将“无盐”和饱和MgSO ₄溶液定殖。6个月后，NaCl饱和和盐杆菌溶液仍然无人居住，但所有其他样品均已定殖。这些实验证明，即使暴露在微生物大气中，某些类型的可居住的液态水环境（即使在地球上）也可以维持数月的繁殖寿命。在其他行星体（例如火星）上，这些数据暗示保留了暂态水体的可能性，该暂态水体会记录可居住的状况，但没有生命迹象，即使生命存在于地球上其他地方也是如此。