Possible evidence of life on Titan
There is some speculation that there is life on Titan, Saturn’s largest moon. The source of this speculation is Chris McKay of NASA’s Ames Research Center and Heather Smith of the International Space University in France.
Titan’s atmosphere is about 5% methane, and Dr. McKay thinks that it could be due to methanogens — strict anaerobes that produce methane as a byproduct of their cellular metabolism. These methanogens would breathe hydrogen from Titan’s atmosphere, and consume organic molecules descending from Titan’s atmosphere as food. The three substances considered as a food source were ethane, tholins, and the most promising, acetylene which yields six time the energy per mole as either ethane or tholins.
Whether or not methanogens exist on Titan remains to be seen. The proof will be when the raw Huygens data is re-analyzed to determine the levels of hydrogen on the surface of the moon. If they are 1/1000th the levels that they are in the atmosphere, there’s a very good chance that there are methanogens present because no known non-biological process would be able to explain the low hydrogen levels. The data has already been collected, all that remains is separating the hydrogen levels out of the rest of the data from when the probe descended to Titan’s surface. If analyzing the hydrogen levels proves too difficult, the team might try to measure the acetylene levels instead, because they too would show a fall off towards the surface:
One hope for testing their idea rests with the data from an instrument on Huygens called the GCMS, which recorded Titan’s chemical make-up as the probe descended. It will take time to analyse the raw data, partly because hydrogen’s signal will have to be separated from those of other molecules. “Eventually, I hope, we will have numbers for at least upper limits for hydrogen,” says Hasso Niemann of Goddard Space Flight Center in Maryland, principal investigator of the GCMS.
Acetylene could be easier to analyse, McKay says, and it too might betray life. “I would guess that there would be a similar fall-off of acetylene if the microbes are eating it.”
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