The comet under study by the European Space Agency's Rosetta spacecraft and Philae lander is the latest target for claims about the possibility of alien life -- but those claims have already been met with skepticism.
"This is one of those things that could be characterized as 'important if true,'" said Seth Shostak, senior astronomer and director of the Center for SETI Research at the SETI Institute. "This is one claim for extraterrestrial life that's literally out there."
The spark for the controversy came on Monday in the form of a presentation at the National Astronomy Meeting, held this week in Wales. And one of the instigators is a well-known figure in the debate over extraterrestrial life: Chandra Wickramasinghe, director of the Buckingham Center for Astrobiology.
He and a colleague, Max Wallis of the University of Cardiff in Wales, contend that characteristics of the dark, carbon-containing crust and underlying ice on Comet 67P/Churyumov-Gerasimenko are consistent with an environment that could harbor microbes. Rosetta has been flying near the comet since last August, and in November it sent out Philae to make an unprecedented landing on the surface.
"Rosetta has already shown that the comet is not to be seen as a deep-frozen inactive body, but supports geological processes and could be more hospitable to micro-life than our Arctic and Antarctic regions," Wallis said in a news release.
He and Wickramasinghe speculated that any microbial communities on the comet should become more active as the comet approaches the sun and warms up. "If the Rosetta orbiter has found evidence of life on the comet, it would be a fitting tribute to mark the centenary of the birth of Sir Fred Hoyle, one of the undisputable pioneers of astrobiology," Wickramasinghe said.
This week's presentation follows up on similar claims made in a research paper published months ago in the Journal of Astrobiology & Outreach. In that paper, Wallis and Wickramasinghe make the astrobiology connection based on the look of features observed on the comet's surface, rather than on any chemical analysis sent back by the Philae lander.
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This isn't the first time Wallis and Wickramasinghe have made bold claims about life from space. "As is well-known by people in the astrobiology community, Wickramasinghe has found what he claims is good evidence for life in all sorts of places," Shostak said.
Back in 2003, Wickramasinghe contended that microbes could survive being blasted into space by an asteroid or comet impact. Wickramasinghe also has suggested that the SARS virus could have come from outer space, and that a meteor explosion was behind the weird red color in rain that fell on a region of southern India in 2001. (An Indian government report determined that the red stuff came from algal spores.)
That background, plus an alternate reading of the evidence from Rosetta, led University of Twente physicist Chris Lee to brand the latest claims as "breathtakingly stupid."
On his Ars Technica blog, Lee said the buildup of carbon on Churyumov-Gerasimenko's surface is a well-known physical phenomenon that doesn't require biology. All you'd need to do is subject the frozen water and the organic molecules in the comet to the sun's radiation during the approach, he said. "With such a reactive mix, almost any carbon layer with any structure you care to think of can and will form," Lee wrote.
Speaking from an astrobiology perspective, Shostak was equally skeptical. "The problem is, I'm not quite sure what it means to say the topological features there are consistent with life," he told NBC News. "Just because it looks like a duck doesn't necessarily mean it has duck biology." (And as it happens, Comet Churyumov-Gerasimenko really does look like a duck.)
Chris McKay, an astrobiologist at NASA's Ames Research Center, noted that the claims from Wallis and Wickramasinghe were highly speculative.
"Certainly the presence of ice and organic solids on comets in general, and on Churyumov–Gerasimenko in particular, is well established. However, jumping from that to microorganisms and even to lakes of liquid water is going well beyond the data," McKay told NBC News in an email. "Of course many speculations that go beyond the data prove to be correct when adequate data is collected. But many more speculations that go beyond the data turn out to be incorrect."
Lee predicted that the claim about the comet would follow the latter course. "This claim will vanish, never to be heard from again," he wrote.