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Titan under a red giant sun: A new kind of “habitable” moon
Author(s) -
Lorenz Ralph D.,
Lunine Jonathan I.,
McKay Christopher P.
Publication year - 1997
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/97gl52843
Subject(s) - astrobiology , titan (rocket family) , haze , planet , atmosphere (unit) , environmental science , circumstellar habitable zone , atmospheric sciences , solar system , methane , physics , astronomy , meteorology , exoplanet , chemistry , organic chemistry
We explore the response of Titan's surface and massive atmosphere to the change in solar spectrum and intensity as the sun evolves into a red giant. Titan's surface temperature is insensitive to insolation increases as the haze‐laden atmosphere “puffs up” and blocks more sunlight. However, we find a window of several hundred Myr exists, roughly 6 Gyr from now, when liquid water‐ammonia can form oceans on the surface and react with the abundant organic compounds there. The window opens due to a drop in haze production as the ultraviolet flux from the reddening sun plummets. The duration of such a window exceeds the time necessary for life to have begun on Earth. Similar environments, with ∼200K water‐ammonia oceans warmed by methane greenhouses under red stars, are an alternative to the ∼300K water‐CO 2 environments considered the classic “habitable” planet.