Life on Titan? -- AMIGA Astronomy

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Subject: Life on Titan?

Author:
Blobrana

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Date Posted: 11:16:01 01/25/05 Tue

On 14 January, the Huygens probe plunged through the Titan�s atmosphere, sending back scientific data. It landed on Titan at around 1138 and transmitted a signal until at least 1555 GMT.
Scientists will comb the data sent back for the chemical signature of life in a bid to identify the moon's source of methane.
Methane is constantly destroyed by UV light so there must be a source within Titan to replenish the atmosphere.
Life could be a possible source of this hydrocarbon along with geological processes.
Titan is too cold for surface biology, but microbes could survive deep within Titan.
Methane can also be released from a trapped form called clathrate and can be produced by a geological process called "serpentisation".
Neither of these involves biology.
Dominated by nitrogen, methane and other organic molecules, Titan resembles a deep-frozen version of Earth 4.6 billion years ago.
Liquid methane rains down on Titan into river channels carved between hills of water ice. Reservoirs of this hydrocarbon probably lie on or just below the surface.
But UV light would destroy all the methane on Titan within 10 million years if it were not being constantly renewed.

"We cannot say there is absolutely no chance for life. Models of Titan's interior show there should be an ocean about 100km deep at around 300km below the surface."

If the models are correct, this ocean would be composed mostly of liquid water with about 15% ammonia at a temperature of about -80C.

"We have liquid water, organics not so far away; we have everything on Titan to make life.�

If methane-producing microbes had colonised this habitable zone, scientists might detect its chemical signature by looking at the relationship of two forms (or isotopes) of the element carbon - C12 and C13.
Living cells preferentially incorporate C12. So compounds produced by living things should be depleted of "heavier" isotopes such as C13, and have a high C12/C13 ratio.
Scientists should be able to measure this ratio in data sent back by the Gas Chromatograph Mass Spectrometer (GCMS) instrument on Huygens.

"The GCMS can directly detect the C12/C13 carbon ratio. We haven't done that yet, but we're working on it".

"It's one factor we can take into account to figure out how methane is getting replenished."

However, scientists favour the geological process of serpentisation as a more likely source of the moon's methane.
In serpentisation, geothermal activity generates methane through the oxidation of metals such as iron, chromium and magnesium which could be contained in crustal rocks below Titan's surface.
Another possibility is that methane molecules are trapped in a water-ice matrix called clathrate (or methane hydrate).

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