2018/03/14 by Arwen Nicholson, Arwen E. Nicholson, David M. Wilkinson +2
Earth and Planetary Sciences · Physics and Astronomy · #Astrobiology #Astronomy #Earth Systems and Cosmic Evolution #Exoplanet #Habitability #Physics #Planet #Planetary Science and Exploration #Planetary habitability #Space Science and Extraterrestrial Life #Terrestrial planet #astro-ph.EP
paper · pdf · doi:10.1093/mnras/sty658
Accepted for publication in MNRAS
openalex publication_date 2018/03/14 · arxiv created 2018/03/23 · arxiv updated 2018/03/28 · openalex created_date 2018/03/29 · openalex updated_date 2026/08/05
The search for habitable exoplanets inspires the question – how do habitable planets form? Planet habitability models traditionally focus on abiotic processes and neglect a biotic response to changing conditions on an inhabited planet. The Gaia hypothesis postulates that life influences the Earth's feedback mechanisms to form a self-regulating system, and hence that life can maintain habitable conditions on its host planet. If life has a strong influence, it will have a role in determining a planet's habitability over time. We present the ExoGaia model – a model of simple ‘planets’ host to evolving microbial biospheres. Microbes interact with their host planet via consumption and excretion of atmospheric chemicals. Model planets orbit a ‘star’ that provides incoming radiation, and atmospheric chemicals have either an albedo or a heat-trapping property. Planetary temperatures can therefore be altered by microbes via their metabolisms. We seed multiple model planets with life while their atmospheres are still forming and find that the microbial biospheres are, under suitable conditions, generally able to prevent the host planets from reaching inhospitable temperatures, as would happen on a lifeless planet. We find that the underlying geochemistry plays a strong role in determining long-term habitability prospects of a planet. We find five distinct classes of model planets, including clear examples of ‘Gaian bottlenecks’ – a phenomenon whereby life either rapidly goes extinct leaving an inhospitable planet or survives indefinitely maintaining planetary habitability. These results suggest that life might play a crucial role in determining the long-term habitability of planets.