Discovered: a new form of life DEC 02 2010
NASA's astrobiology announcement is that they've found a new kind of life that incorporates the normally toxic arsenic into its DNA.
Life like us uses a handful of basic elements in the majority of its biochemistry: carbon, hydrogen, oxygen, and nitrogen for the most part. But phosphorus is also a critical element in two major ways: it's used as the backbone of the long, spiral-shaped DNA and RNA molecules (think of it as the winding support structure for a spiral staircase and you'll get the picture), and it's part of the energy transport mechanism for cells in the form of ATP (adenosine triphosphate). Without it, our cells would literally not be able to reproduce, and we'd be dead anyway if it were gone. There are many other ways phosphorus is used as well, including in cell membranes, bones, and so on. It's a key element for all forms of life.
Amazingly, using radioisotope-tagged molecules containing arsenic, they were able to find that the microbes incorporated the arsenic into their very DNA! It's hard to stress how shocking this is; as I understand it, saying something like that to a microbiologist without evidence would've had them slowly backing away from you and looking for weapons or an escape route.
I guessed wrong about what NASA was set to announce today, but the actual announcement is much more interesting than the mere discovery of extraterrestrial life. Aliens are inevitable -- we're going to find them sooner or later -- but a new kind of DNA, that's not something that happens every day. Exciting! (thx, jon)