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Arsenic based life 7 April, 2011

Posted by Simon Nickerson in Uncategorized.

Back in late November, NASA put out a press release about an upcoming news conference. The exact details of the research to be discussed weren’t revealed, because the research paper wasn’t published yet, but the release stated that the news conference would discuss

…an astrobiology finding that will impact the search for evidence of extraterrestrial life.

This vague wording sparked some wild speculation in the popular press.

Eventually it was revealed that a NASA-funded research team, led by Felisa Wolfe-Simon, had discovered microbes in California’s Mono Lake that appeared to have a slightly different kind of DNA from all other known living things. Mono Lake is an unusual (and hostile) environment – it’s about twice as salty as the oceans, extremely alkaline, and has very high levels of arsenic. Some microbes in Mono Lake are capable of using arsenic instead of water to help them photosynthesise, but this new research identified microbes that are actually incorporating arsenic into their DNA, in the place of phosphorus.

There’s many different angles to this story, but for now I’ll focus on the science and the media.

Almost immediately the experimental process came under attack – Rosie Redfield wrote a detailed review of the paper here. The main point of criticism was that the researchers simply weren’t careful enough with their experiment, so the conclusion can’t be trusted.  From her conclusion:

Lots of flim-flam, but very little reliable information.  The mass spec measurements may be very well done (I lack expertise here), but their value is severely compromised by the poor quality of the inputs.  If this data was presented by a PhD student at their committee meeting, I’d send them back to the bench to do more cleanup and controls.

I don’t know whether the authors are just bad scientists or whether they’re unscrupulously pushing NASA’s ‘There’s life in outer space!’ agenda.  I hesitate to blame the reviewers, as their objections are likely to have been overruled by Science’s editors in their eagerness to score such a high-impact publication.

NASA’s approach to publicising this research – putting out a teasing press release and letting the wild ideas build up before announcing the results – has angered a lot of scientists and no doubt fuelled some of the criticism. During the days leading up to the press conference, those who had actually read the paper couldn’t jump in and tamp down some of the speculation, because the paper was still under an embargo.

For some excellent summaries of the whole saga, see Carl Zimmer in Slate here, and the prolific Ed Yong at Discover here, here, here and here. In a recent update, Michael Eisen attended a seminar with Wolfe-Simon and was disappointed with her response to the criticisms.

So what do I make of all this? I think it’s probably an unfortunate mix of too much hype and sloppy science. Sounds similar to ALH84001, but in that case the debate was mostly about how to interpret observations, and that can take a long time to resolve. Here the main issue is the experimental process, and that can be resolved relatively quickly if others attempt to replicate the results – it will be interesting to see if there are any takers.



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