The much-anticipated NASA news conference is now over, so what was revealed, exactly? Not alien life (yet), but still an astrobiology-related finding on Earth that will greatly affect the search, just as the initial NASA press release stated. There was, again, a lot of overblown speculation, mostly on the part of various media and bloggers, that such life itself had been confirmed finally, although this was not based on the known facts at the time.
As most serious researchers, bloggers, etc. had surmised, it was a more down-to-earth discovery, but still indeed significant. The consensus that it had to do with a possible shadow biosphere, as mentioned in my previous post, was not too far off. The discovery involves bacteria that can substitute arsenic (usually extremely toxic) for phosphorus, one of the six elements normally found in all known life (on Earth anyway); the others being carbon, hydrogen, nitrogen, oxygen and sulfur. The six building blocks of life as we know it. Or perhaps knew it, now.
The bacteria, GFAJ-1, found in arsenic-rich Mono Lake, California, are the first to be observed doing this. The key is that the bacteria apparently don’t just tolerate the arsenic as other organisms can do, but they seem to actually incorporate it into their DNA and cellular structure in place of the phosphorus. The studies are still on-going, and there is the usual, but necessary, skepticism from others in the scientific community, but if the results are confirmed by others, it will redefine what forms life can take, and increase the variety of environments where such life could exist outside of Earth, such as Titan (whose cold but wet methane environment would be more suited for arsenic-based life according to some recent studies), Mars, Enceladus, etc.
Some scientists are arguing that this has more to do with adaptation than a unique form of evolution, hence not a true shadow biosphere or “second genesis” (truly unique life which arose completely independently of all other known life on Earth). Even if so, it is still yet another example of the increasingly wide types of environments life can be found in, notably those long thought to be too toxic. And from that we can only learn more.