The Sirens of Titan

Saturn's moon Titan has long been a strong contender as a place to look for life beyond Earth. It is extremely cold (daytime highs in the 90s -- that's degrees Kelvin, of course; about -180 Centigrade) but it has a dense atmosphere and the Cassini probe confirmed the existence of methane lakes on the surface. It's very rich in complicated organic molecules, the sort which on Earth are intimately involved with living things as precursors or products.

Just recently Cassini found something much more interesting about Titan. Its atmosphere is missing some things. Specifically, the amount of hydrogen at the surface is lower than elsewhere, and there isn't any acetylene. This is bad news for welding contractors in the outer Solar System, but it's intriguing to biologists interested in life beyond Earth, because this suggests something is using the hydrogen and acetylene.

This certainly bears more looking into. Life on Titan would be very different from life on Earth, and would be unlikely to share any common source. Instead of DNA it might encode its genetic information in complex hydrocarbon molecules. Getting a look at an entirely different kind of life would tell us a great deal about how our own kind works. And since there are probably a lot more cold worlds like Titan in the universe than warm water-covered garden spots like Earth, hydrocarbon life might be a lot more common than DNA/water life like us.