Argh. Once again, the biggest science story of the week is a bit of a mess. NASA didn't help by teasing everyone with its advance press release/PR stunt about an "astrobiology discovery." The news was nothing of the sort. Rather, scientists have found some very weird life—on Earth.
The real story is fascinating, if you're into biology. Bacteria that appear to be able to substitute arsenic in place of phosphorus in the very structure of their DNA (and other bioactive molecules)—that's extremely cool. It shows how innovative natural selection can be, because as PZ Myers points out, the reason arsenic is usually lethal to living things is precisely because it's chemically so similar to phosphorus (and nitrogen). Usually, however, it screws up biochemical processes that it gets mixed into. These newly-discovered bacteria from salty, alkaline Mono Lake in California have managed to co-opt arsenic instead of being killed by it.
But the publicity and news coverage remind me of the hoopla over Ida and Ardi, the fossil primate discoveries touted last year. Again, cool science, but woefully misrepresented to the public in its importance and meaning. The connection between the GFAJ-1 bacteria from Mono Lake and potential extraterrestrial life (which, I remind you, no one has yet found any evidence of) is so tenuous it's almost nonexistent: these critters tell us that it's possible for life to use a slightly different chemistry.
But we're not talking about life based on silicon instead of carbon. This is a less fundamental difference. The bacteria in question still use DNA. In the wild, in Mono Lake, they still use phosphorus, and indeed they're healthiest when they do. But in the lab, they can be coaxed into using arsenic instead, rather than simply dying in messy heaps like the rest of us earth beings would. Those are the basics.
I guess it makes sense, in a way, for NASA to hype up the story. A press release titled "Biologists discover life can use slightly different chemistry" wouldn't bring out CNN, but hype also has its risks:
The problem is that hype can lull us into a cry-wolf syndrome. If people hear about an amazing set of "missing links!!!" (but oh, they aren't) and "signs of extraterrestrial life!!!" (but oh, they're terrestrial), are we going to take it seriously when scientists say, for instance, "Hey, global climate change looks like it's going to be a big problem"?
Many policy makers in the U.S. and elsewhere are already too ignorant about important scientific issues today, even about such essential ideas as how petroleum forms, the reality of evolution, or the usefulness of paying for basic research. Bait-and-switch tactics with scientific announcements surely don't help.