I recently speculated that spacecraft both orbiting and sitting upon Mars may have already detected signs of life. In particular, some spacecraft have detected signs of methane:
In 2004 the European Space Agency probe Mars Express detected the presence of methane in the atmosphere of Mars. Methane can be produced geologically (and Mars is not short on volcanoes), or biologically. (Though media reports of that observation got a bit out of hand.) Either way, this is an important observation and research on the source of this methane is still ongoing.
The existence of methane is ambiguous: Though methane is produced biologically, as I wrote above, it’s also produced geologically (and, in fact, the methane detected on Mars tends to be both localized and emanating from some of the more volcanic regions). It can also be delivered by comets. Given its ubiquity, methane may raise hopes, but in the end turn out to be a poor biomarker. Detecting life elsewhere will require multiple lines of evidence.
Planets and moons do not give up their secrets willingly or easily — they make us work for every clue we get. That seems particularly true when it comes to the search for extraterrestrial life. Even then, some bodies in the Solar System make us work harder than others.
Take Titan, for example. Two weeks ago, I wrote that observations of Titan from Cassini have been interpreted by some as possible signs of life, in particular:
Now it turns out that computer simulations based upon Cassini observations, simulations which hint at depletions of various chemical species at Titan’s surface may again hint at the possibility of life on Titan. The results are very preliminary, but fascinating nevertheless.
It’s highly unlikely that we’ll ever be able to make a positive determination if there’s life on Titan based upon Cassini data alone. Cassini is, after all, an orbiter, and its observations of Titan’s surface come from hundreds, even thousands, of kilometers away–limited to those that can be attained during flybys. To ascertain the presence of life, we’ll need what scientists in the field of remote sensing call “ground truth”–we’ll have to wait until we are able to send a followup probe to the surface of Titan. Perhaps we’ll send a probe to Titan similar to Tiny–the Titan rover who has guest-starred in episodes of this season’s Eureka.
Even then it could turn out that, unless NASA’s version of Tiny returns samples to Earth for human examination, the results could remain ambiguous and leave scientists scratching their heads. That is what’s happening with Mars.
Titan hides its secrets beneath a thick photochemical haze, but when it comes to planets that jealously guard their secrets, Mars is the champion. The Great Galactic Ghoul of Mars destroys our spacecraft. Mars throws us curve balls; Mars lies to us. Mars even laughs at the spacecraft it does allow to explore it.