erm, is it definately native? could this be literally alien?
Mitch,
Yes, it could be literally alien having come to us on a meteorite or something, but we would have know by now with a high degree of certainty. We could tell that by sequencing its DNA and I am sure we have already done that, since the interesting thing about the critter is that it uses arsenic in making amino acids rather than phosphorous.
The reason why we could tell with such certainty is that one of the pillars that support the notion that all life on the planet has descended from a common life form (or forms) is that they all use the same universal genetic code.
Besides the fact that all life on earth seems to use either RNA or DNA as its genetic database, the amino acid combinations that all life uses is also universal. Given that the number of informationally equivalent alternative codes number in the 10^70 (ten to the power of 70), any life form that is not descended from the first life forms on earth would be immediately obvious.
This is because the chances of it using the same unversal genetic code without having descended from the first life forms that earth life did, would be one in 10^70.
So that rules out the possiblity that it fell to earth in a meteorite having evolved independently in some other way that puts it outside the family tree of life on earth.
However, as solid as the notion of common descent is, the question of abiogenesis (the origin of the first life form or forms) is highly speculative. That leaves open the possibility that the first life forms that all life evolved from on earth came from somewhere else having seeded the earth so many billions of years ago. (this is called the "panspermia hypothesis").
And this leaves open the possibility that this critter evolved from the same first life forms that earth life did, but the first life forms themselves lived somewhere else outside of our planet. In other words, the tree of life on earth is intact, but the roots of it are not from earth and this critter shares a very early exobiological common ancestor.
But finally, there is no suggestion that this guy is different enough for that to be a bigger question for this critter than some other life forms on earth. It simply has figured out how to metabolize arsenic instead of phosphorous and it may have done that recently rather than billions of years ago.
After all, we have bacteria that has evolved on its own to eat nylon and other recent created synthetic compounds, so the arsenic trick is not so special to suspect it is an alien.
As I said before, the big story is not that it metabolizes arsenic so much as that we just never anticipated something that. It says more about our limited vision that it does about the uniqueness of this critter.
And it is not that we are suprised by our limited vision, either. There is a field called "exobiology" which is the study of life forms from outside of the earth. You might be say that a field like that is as ridiculous as "unicornology" given that we have no examples of exobiology. But the field is also involved in speculating what other kinds of biochemistry might be possible. Carl Sagan was an exobiologist who did this sort of thing, for example.
As the article in the OP implied, such speculation is important if you want to search for life outside of our planet. We expect that life to have different biochemistry, but lacking knowledge of what that might be, we don't know what to look for in terms of a viable environment or viable signs of that life itself.
What this arsenic critter told us that that this is also true to some extend here on earth. We have life around us on earth that we are not tuned in to be looking for.
But it is not really possible for us to judge if our speculations on other kinds of alien biology are very visionary or very naive. I think the reason why the arsenic critter is getting so much press, is that it demonstrates that we are way over on the naive side of the spectrum rather than the visionary one.
Once we analyzed the mechanism it uses for metabolizing arsenic we said, "Oh, yeah. Why didn't we think of that before?". You see what I mean? We were surprised more by our lack of vision than we were the uniqueness of the arsenic critter.
Finally, I don't want to sound dismissive of this finding as if I know it all. I find it amazing and fascinating but not because it might be alien. I think it deserves all the press it is getting and I think it reminds people how miraculous life is to begin with.