Swansong biospheres: refuges for life and novel microbial biospheres on terrestrial planets near the end of their habitable lifetimes
Swansong biospheres: refuges for life and novel microbial biospheres on terrestrial planets near the end of their habitable lifetimes
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DOI：
10.1017/s147355041200047x
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发表时间：
2013-04-01
影响因子：
1.7
通讯作者：
Cockell, Charles S.
中科院分区：
文献类型：
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作者：
O'Malley-James, Jack T.;Greaves, Jane S.;Cockell, Charles S.
未来地球上的生物圈（和过去一样）将主要由单细胞微生物组成。在多细胞生命出现之前，单细胞生命可能存在了至少2.5 Gyr，并且可能是唯一能够在遥远的未来在地球上生存的生命形式，当老化的太阳导致环境条件变得更加不利于更复杂的生命形式时。因此，从统计学上看，我们发现的可居住的类地系外行星更有可能处于其可居住寿命中更有利于支持单细胞生命而不是多细胞生命的阶段。地球上可居住性的最后阶段是这项工作的重点。一个简单的，纬度为基础的气候模式，包括偏心率和偏心率的变化被用来作为一个指南，在未来3 Gyr的地球温度演变。这使得人们可以推断出潜在的生命避难所，特别是在山区和冷阱（冰）洞穴中，以及什么样的生命形式可以生活在这些环境中。结果表明，在高纬度地区，单细胞生命可以持续到2.8 Gyr。这开始回答地球的可居住性将如何随着太阳的主序星演化而在局部尺度上演化的问题，以及通过扩展，类地行星的可居住性将如何随着时间的推移与它们自己的宿主恒星一起演化。
The future biosphere on Earth (as with its past) will be made up predominantly of unicellular micro-organisms. Unicellular life was probably present for at least 2.5 Gyr before multicellular life appeared and will likely be the only form of life capable of surviving on the planet in the far future, when the ageing Sun causes environmental conditions to become more hostile to more complex forms of life. Therefore, it is statistically more likely that habitable Earth-like exoplanets we discover will be at a stage in their habitable lifetime more conducive to supporting unicellular, rather than multicellular life. The end stage of habitability on Earth is the focus of this work. A simple, latitude-based climate model incorporating eccentricity and obliquity variations is used as a guide to the temperature evolution of the Earth over the next 3 Gyr. This allows inferences to be made about potential refuges for life, particularly in mountains and cold-trap (ice) caves and what forms of life could live in these environments. Results suggest that in high latitude regions, unicellular life could persist for up to 2.8 Gyr from present. This begins to answer the question of how the habitability of Earth will evolve at local scales alongside the Sun's main sequence evolution and, by extension, how the habitability of Earth-like planets would evolve over time with their own host stars.