At their conference today, NASA scientist Felisa Wolfe Simon will announce that they have found a bacteria whose DNA is completely alien to what we know today. Instead of using phosphorus, the bacteria uses arsenic. All life on Earth is made of six components: carbon, hydrogen, nitrogen, oxygen, phosphorus and sulfur. Every being, from the smallest amoeba to the largest whale, share the same life stream. Our DNA blocks are all the same.
But not this one. This one is completely different. Discovered in the poisonous Mono Lake, California, this bacteria is made of arsenic, something that was thought to be completely impossible. While she and other scientists theorized that this could be possible, this is the first discovery. The implications of this discovery are enormous to our understanding of life itself and the possibility of finding beings in other planets that don't have to be like planet Earth.
[T]hey had discovered an earthly life form that used a radically different chemistry. I was dubious, even at that. And then I finally got the paper from Science, and I'm sorry to let you all down, but it's none of the above. It's an extremophile bacterium that can be coaxed into substituting arsenic for phosphorus in some of its basic biochemistry. It's perfectly reasonable and interesting work in its own right, but it's not radical, it's not particularly surprising, and it's especially not extraterrestrial. It's the kind of thing that will get a sentence or three in biochemistry textbooks in the future.