Thermodynamic Constrains for Life Based on Non-Aqueous Polar Solvents on Free-Floating Planets |
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Authors: | Viorel Badescu |
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Institution: | (1) Candida Oancea Institute, Polytechnic University of Bucharest, Spl. Independentei 313, Bucharest, 060042, Romania |
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Abstract: | Free-floating planets (FFPs) might originate either around a star or in solitary fashion. These bodies can retain molecular
gases atmospheres which, upon cooling, have basal pressures of tens of bars or more. Pressure-induced opacity of these gases
prevents such a body from eliminating its internal radioactive heat and its surface temperature can exceed for a long term
the melting temperature of a life-supporting solvent. In this paper two non-aqueous but still polar solvents are considered:
hydrogen sulfide and ammonia. Thermodynamic requirements to be fulfilled by a hypothetic gas constituent of a life-supporting
FFP’s atmosphere are studied. The three gases analyzed here (nitrogen, methane and ethane) are candidates. We show that bodies
with ammonia oceans are possible in interstellar space. This may happen on FFPs of (significantly) smaller or larger mass
than the Earth. Generally, in case of FFP smaller in size than the Earth, the atmosphere exhibits a convective layer near
the surface and a radiative layer at higher altitudes while the atmosphere of FFPs larger in size than Earth does not exhibit
a convective layer. The atmosphere mass of a life-hosting FFP of Earth size is two or three orders of magnitude larger than
the mass of Earth atmosphere. For FFPs larger than the Earth and specific values of surface pressure and temperature, there
are conditions for condensation (in the ethane atmosphere). Some arguments induce the conclusion than the associated surface
pressures and temperatures should be treated with caution as appropriate life conditions. |
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