The Geology of Mars and of Titan: A Tale of Two Worlds
Devon M. Burr, SETI Institute

Planetary geology provides critical information of other worlds, including their astrobiological potential. By that term, I mean not only their specific potential to harbor life but their more general potential to tell us something about life. As we expand our understanding of life – where it is, what it is, how it is – beyond Earth, geology complements other information (e.g., compositional data from spectroscopy) in giving us clues as to planet habitability. Mars is a case in point: the earliest to most recent data show unmistakable evidence of water, the sine qua non for all life that we know. These remote and (recently) in situ data indicate large volumes of water in the surface, subsurface and atmosphere throughout Mars’ history. Yet evidence in these data for organic materials is stubbornly lacking. In contrast, data of Titan, Saturn’s largest moon, show a persistent lack of liquid water, as is expected from its size and position relative to the Sun. Yet this world is drenched in organic compounds. As part of its hydrocarbon cycle (analogous to Earth’s hydrologic cycle), Titan forms organic molecules in the upper atmosphere, which apparently result on the surface in extensive aeolian (wind-formed) dunes. Thus, Mars and Titan each provide disparate but important astrobiological information. In this part of the Planetary Habitability session, I will give an overview of some of the most recent geologic discoveries regarding water on Mars and organics on Titan, as relevant to understanding planetary habitability.

For background reading, see
“The Limits of Organic Life in Planetary Systems” NAS report 11919

“An Astrobiology Strategy for the Exploration of Mars” NAS report 11937

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