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NASA announced 'An Astrobiological finding that will impact the search for evidence of extraterrestrial life'
http://www.sciencemag.org/content/ear...
An astrobiological finding? Really? not just an interesting study of some extremophile bacteria in Mono Lake?
While the results and the research are both interesting, the oversell in unjustified based on it.
Specifically speculating about arsenate based DNA based on....... well not a lot really. Some EXAFS that shows little more beyond the model sensitive stuff kicks in that its tetracoordinate. Now they claim they can tell the difference between that and the AsO4 anion and its variants, but EXAFS is really pretty model dependent stuff for anything beyond the first shell.
They also do some phenol-chloroform analysis and some other fairly standard biochemistry, all based on the assumption, which is a very shakey one, that IF they have arsenic DNA, then it will behave in a similar fashion to regular DNA.
The irony is this woman, Felisa Wolfe-Simon, claims in the press conference to have read all the seminal paper etc etc including Watsons n Cricks paper on the structure of DNA, leading to the bloody obvious Q. why not just do the fiber diffraction patter, then QED. I mean IF they have what they say, its a crystallographers wet dream with all those heavy atom substitutions!
A lot of the oversimplistic view of biochemistry really rubbed me up the wrong way. Getting overly worked up about which chemicals are present and which ones are not seems kinda trivial. The work in itself is interesting enough without this sort of claim, the more so as this facile overview of biochemistry is only much use for noobs.
I mean if this trivial stamp collecting is what NASAs into, you can substitute Se for S in many proteins, and indeed the crystallographers love this sort of heavy atom substitution.... should we call a press conference of astrobiology for this too? Similarly for various ion substitutions.
Loads of the technical detail of the paper bugged me too, the way they always refer to phosphate and arsenate explicitly as the 3- ions, even when they are incorporated into molecular structures. They classification of the phosphate and arsenate species present also represented significant biochemistry thinking. Looks like most the basisity of the solution comes from the carbonate, but some sort of estimate of the various concentrations of the various protonation states of the oxyanion in these solutions would have been nice (relatively trivial to calculate). Basically saying what you gurgled into these solutions is not as useful as what exists in the solutions you used.
Finally I have grave doubts about the premature nature of this data, and couldnt help but feel the shadow of Pons and Fleischman. Big PR announcements that turn out to be bogus just undermine the publics confidence in science, when civilization needs it as never before.
I sincerely hope Felisa is right here, for all our sakes. If I was asked what my estimate of an organism being able to absorb this sort of structural shock in a few generation going from an entirely phosphate based backbone to arsenate (given that this will mostly likely have BIG effects in both histone binding, and transcription, the factors that determine the production of proteins) I would be giving it a chance (generously) in the few percent range. Biochemistry is REALLY picky over structure.\---------------------
Kind of sad that NASA would make such a claim without any supporting evidence. Perhaps they were just looking for some attention from the media? For NASA also to use the term 'extraterrestrial life' a lie. The life form they found both originated and lives on the same planet we do.
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