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Alien life revisited

Science / AAAS

A photomicrograph shows a strain of bacteria called GFAJ-1 that was said to incorporate arsenic into its cellular machinery.

Last updated 2:15 p.m. April 2:

Is there life beyond Earth? Over the past few months, scientists have repeatedly suggested that there could be — but the science behind those suggestions remains frustratingly murky and controversial.

Astrobiology's X-Files were the subject of a talk I gave on Saturday in the Second Life virtual world, at the invitation of the Meta Institute for Computational Astrophysics. Here's the vidcast of the talk — which gives you a taste of how Second Life works as well as how the search for extraterrestrial life works.

Arsenic life
This talk came exactly four months after researchers shook up the scientific world with claims that they were able to get the cellular machinery of microbes from California's Mono Lake working with arsenic instead of phosphorus. That's an amazing result, because arsenic is supposed to be poisonous to living things. If organisms on Earth could be tweaked in such a dramatic way, perhaps life could arise in other environments that don't seem conducive to life as we know it ... the Saturnian moon Titan, for example.

The implication of the research, published in the journal Science, would be that we might be missing strains of "weird life" that just might exist under our noses. (Perhaps literally under our noses, as a "second Genesis" that has gone undetected.)

The study ran into a lot of skepticism from the start. Some microbiologists and chemists have faulted the research team's laboratory techniques, or the conclusions that the team drew from their data. In response, the research team insisted their science was sound — but also encouraged their detractors to run their own experiments and report the results. Science pledged to publish a follow-up.

That follow-up is still in the works, but commentaries on the "arsenic life" are showing up in peer-reviewed journals such as BioEssays and FEMS Microbiology Letters. These papers have sparked a secondary controversy: Does scientific criticism really count if it's just on the Internet?

The BioEssays paper sees no "fatal flaw" in the original paper, and the paper's authors contend that Internet-only discussions "are not components of the peer-reviewed literature and thus are not placed on record as part of the official scientific discourse." The Microbiology Letters commentary complains about "the magic and nonsense that floods cyberspace."

As you can imagine, that's sparked a lot of counter-criticism from the folks who have been using the blogosphere and Twittersphere as a sounding board for their own review of the research. To get that side of the story, check out the postings from Rosie Redfield at the University of British Columbia, Zen Faulkes from the University of Texas-Pan American and Michael Eisen from the University of California at Berkeley (who attended an informal seminar given by Felisa Wolfe-Simon, the lead author of the arsenic-life study).

R. Hoover / Journal of Cosmology

A field-emission scanning electron micrograph shows one of the filaments that was found in the Ivuna CI1 carbonaceous meteorite. The filament looks similar to those seen in earthly cyanobacteria.

Meteorite life
Less than a month ago, NASA astrobiologist Richard Hoover published a paper in the online-only Journal of Cosmology, suggesting that a number of meteorites contained microbes that could have come from outer space. Once again, the study created a splash, in large part because of the NASA connection. There was quite a furor over whether or not Hoover was misinterpreting what he was seeing, and some critics pointed out that the research had been submitted to (and rejected by) other, better-known journals before it wound up in the Journal of Cosmology.

The story went big on a Saturday, but by the following Monday, executives at NASA disavowed the research, and the debate quickly died down. The Journal of Cosmology's editors said they were selling off the publication. Hoover, who has had a long and distinguished career as a researcher at NASA's Marshall Space Flight Center, faced sharp questions about his academic credentials.

Today, Hoover came in for an added dose of indignity: The James Randi Educational Foundation named him one of the year's "five worst promoters of nonsense," alongside anti-vaxxer Andrew Wakefield, televangelist Peter Popoff, TV doctor Mehmet Oz and the CVS pharmacy chain (for offering homeopathic remedies). The last thing Hoover needs right now is a "Scientist Pigasus Award" from the Amazing Randi.


Some scientists have suggested that tiny wormlike structures seen within the Mars meteorite known as ALH84001 may be "nanofossils" of biological origin.

Life on Mars
You could argue that the sharp debate over the prospects of detecting microbial life from beyond Earth began 15 years ago, with Science's 1996 publication of research about "nanofossils" found in a meteorite from Mars. Some might go two decades further back, to the much-debated life-detection experiments that went to Mars aboard the Viking landers.

Even after 15 years, the microfossil debate is still percolating. The researchers behind the original study have been setting out other lines of evidence to argue that they're seeing the fossilized traces of ancient organisms rather than modern-day contamination from Earth, or geological shapes that just happen to look like critters.

Other studies, conducted as part of NASA's Phoenix Mars Lander mission, have shown the presence of perchlorate, a chemical that could be associated with particular kinds of exotic life on Earth. Those findings have revived discussions over what Viking found (or failed to find).

Although the debate over past life-on-Mars experiments is continuing, most astrobiologists say it's going to take additional  studies on the Red Planet to resolve the controversy. That's the goal of an experiment being proposed by MIT and Harvard researchers, known as the Search for Extra-Terrestrial Genome, or SETG. Right now the researchers are facing one big challenge: They don't yet have a spot on a future Mars probe.

Even if SETG's genome sequencer went to Mars and detected a snippet of DNA or RNA, would that serve as sufficient evidence that life arose on other planets? Or would such a claim end up in the same limbo that surrounds earlier claims for alien life. I suspect that the latter would be the case — but what do you think? Feel free to weigh in with your comments below, and check out Saturday's hourlong presentation.

More controversies in astrobiology:

Join the Cosmic Log community by clicking the "like" button on our Facebook page or by following msnbc.com science editor Alan Boyle as b0yle on Twitter. To learn more about my book on Pluto and the search for planets, check out the website for "The Case for Pluto."