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Beyond Earthly Skies

Deep Alien Biospheres

23 Nov 2013, 09:40 UTC
Deep Alien Biospheres
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Life on Earth not only exists on the surface, but it also includes a subsurface biosphere extending several kilometres in depth. At such depths, the only reasonable source of energy to sustain life comes from the planet's own internal heat. Indeed, a planet that is located far from its host star, resulting in surface temperatures too cold to support life, can potentially harbour a thriving subsurface biosphere that is sustained solely by the planet's own internal heat.Figure 1: Artist’s impression of a terrestrial planet. Figure 2: Artist’s impression of a terrestrial planet. Credit: Kevin Sherman.A study by S. McMahon et al (2013) show that subsurface liquid water maintained by the internal heat of a planet can support an underground biosphere even if the planet is too far from its host star to support life on the planet's surface. The authors introduce a term known as the “subsurface-habitability zone” (SSHZ) to denote the range of distances from a star where a terrestrial planet (i.e. a rocky planet like the Earth) can sustain a subsurface biosphere at any depth below the surface down to a certain maximum habitable depth. This maximum depth depends on numerous factors, but in general, it is the ...

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