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Alien biochemistry on Titan

Ben Moore, Director Center for Theoretical Astrophysics and Cosmology and Leader Project 6 of NCCR PlanetS.

Ben Moore, Director Center for Theoretical Astrophysics and Cosmology, University of Zürich.

Titan is a large moon of Saturn discovered in 1655 by Christiaan Huygens with a two inch telescope. It is a cold world. At its distance from the Sun it receives just one percent of the sunlight that Earth receives and its surface is a chilly minus 180 centigrade! In December 2004 the Cassini-Huygens twin probe split into two parts. The Cassini half continued as an orbiter, whereas the Huygens probe was destined for the surface of Titan. The radar images from Cassini orbiter and the photographs from Huygens landing probe were spectacular. The landscape was covered with hydrocarbon seas, lakes and tributary networks filled with liquid ethane, methane and nitrogen.

On Titan, methane could play the role of liquid water and molecular hydrogen could take the role of gaseous carbon dioxide. The air on Titan has a similar pressure as on Earth, but a very different composition. Life could exist in the lakes of liquid methane on Titan. Although all living things on Earth use liquid water as a solvent, life on Titan might use a liquid hydrocarbon, such as methane or ethane. Hydrocarbons are less chemically active than water, which can break down complex molecules through hydrolysis. Creatures on Titan might use silicon instead of carbon, inhale hydrogen in place of oxygen, metabolise it with acetylene instead of glucose, and exhale methane instead of carbon dioxide. Titan is wonderful example of a nearby world where life may have evolved independently from Earth and with a completely different biochemistry – let’s go back and explore further!

Ben Moore
Leader Project 6

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