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Volume 147, 2010
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Titan and habitable planets around M-dwarfs

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Abstract

The Cassini–Huygens mission discovered an active “hydrologic cycle” on Saturn's giant moon Titan, in which methane takes the place of water. Shrouded by a dense nitrogenmethane atmosphere, Titan's surface is blanketed in the equatorial regions by dunes composed of solid organics, sculpted by wind and fluvial erosion, and dotted at the poles with lakes and seas of liquid methane and ethane. The underlying crust is almost certainly water ice, possibly in the form of gas hydrates (clathrate hydrates) dominated by methane as the included species. The processes that work the surface of Titan resemble in their overall balance no other moon in the solar system; instead, they are most like that of the Earth. The presence of methane in place of water, however, means that in any particular planetary system, a body like Titan will always be outside the orbit of an Earth-type planet. Around M-dwarfs, planets with a Titan-like climate will sit at 1 AU – a far more stable environment than the ∼0.1 AU where Earth-like planets sit. However, an observable Titan-like exoplanet might have to be much larger than Titan itself to be observable, increasing the ratio of heat contributed to the surface atmosphere system from internal (geologic) processes versus photons from the parent star.

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Article information


Submitted
30 Mar 2010
Accepted
12 Apr 2010
First published
02 Jul 2010

Faraday Discuss., 2010,147, 405-418
Article type
Paper

Titan and habitable planets around M-dwarfs

J. I. Lunine, Faraday Discuss., 2010, 147, 405
DOI: 10.1039/C004788K

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