As a number of newspapers have reported over the last few days, there might be life on Titan. The chemical composition of the atmosphere (not so much acetylene, no so much hydrogen near the ground) matches one theory about how life just a little different from terrestrial organisms could be eking out its existence in the cold methane lakes, breathing hydrogen, in the orbit of Saturn.

But Cassini’s corroborating measurements do have other possible interpretations.

It is possible that the hydrogen is combining with carbon in molecules on Titan’s surface to make methane. But at the low temperatures prevalent on Titan, these reactions would normally occur too slowly to account for the disappearing hydrogen.

Similarly, non-biological chemical reactions could transform acetylene into benzene – a hydrocarbon that the VIMS instrument did observe on Titan’s surface. But in that case, too, a catalyst would be needed to boost reaction rates enough to account for the dearth of acetylene.

“Scientific conservatism suggests that a biological explanation should be the last choice after all non-biological explanations are addressed,” says Mark Allen of NASA’s Jet Propulsion Laboratory in Pasadena, California. “We have a lot of work to do to rule out possible non-biological explanations.”

Jonathan Lunine of the University of Arizona in Tucson, a member of Clark’s team, agrees. But he says it may not be possible to distinguish between biological and non-biological explanations without additional missions to Titan. “The only way to know for sure would be to actually get hold of an organism and show that it is alive,” he told New Scientist.

http://www.newscientist.com/article/dn19005-hints-of-life-found-on-saturn-moon.html