Exomoon climate models with the carbonate-silicate cycle and viscoelastic tidal heating
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The habitable zone for exomoons with Earth-like properties is a non-trivialmanifold, compared to that of Earth-like exoplanets. The presence of tidal heating, eclipses and planetary illumination in the exomoon energy budget combine to produce both circumstellar and circumplanetary habitable regions. Analytical calculations suggest that the circumplanetary habitable region is defined only by an inner edge (with its outer limits determined by orbital stability). Subsequent calculations using 1D latitudinal climate models indicated that the combined effect of eclipses and ice-albedo feedback can produce an outer edge to the circumplanetary habitable zone. But is this outer edge real, or an artefact of the climate model's relative simplicity? We present an upgraded 1D climate model of Earth-like exomoon climates, containing the carbonate-silicate cycle and viscoelastic tidal heating. We conduct parameter surveys of both the circumstellar and circumplanetary habitable zones, and we find that the outer circumplanetary habitable edge remains provided the moon's orbit is not inclined relative to that of the planet. Adding the carbonate-silicate cycle pushes the circumplanetary habitable zone outwards, by allowing increases in atmospheric partial pressure of carbon dioxide to boost the greenhouse effect. Viscoelastic tidal heating widens the habitable zone compared to standard, fixed-Q models. Weakening the tidal heating effect due to melting allows moons to be habitable at higher eccentricity, and pushes the inner circumstellar and circumplanetary habitable zone boundary inwards.
Forgan , D & Dobos , V 2016 , ' Exomoon climate models with the carbonate-silicate cycle and viscoelastic tidal heating ' Monthly Notices of the Royal Astronomical Society , vol 457 , no. 2 , pp. 1233-1241 . DOI: 10.1093/mnras/stw024
Monthly Notices of the Royal Astronomical Society
© 2016 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. This work is made available online in accordance with the publisher’s policies. This is the final published version of the work, which was originally published at: https://dx.doi.org/10.1093/mnras/stw024
DF gratefully acknowledges support from the ‘ECOGAL’ ERC advanced grant. VD has been supported by the Hungarian OTKA grant K104607, the Lend¨ulet-2009 Young Researchers Program of the Hungarian Academy of Sciences, the ESA PECS contract No. 4000110889/14/NL/NDe, the T´ET-14FR-1-2015-0012 project, and the NKFIH K-115709 grant of the Hungarian National Research, Development and Innovation Office.