‘Extraordinary claim’ met with skepticism

By Ron Cowen

Web edition: March 9, 2011

A NASA scientist created quite a buzz earlier this week with a claim that he may have found evidence of extraterrestrial life — fossils of bacteria — in three meteorites. But several scientists question the work, which has not been peer reviewed and appeared March 5 in an unorthodox online journal, the Journal of Cosmology. The journal, which began publishing in 2009, has issued a press release that it will go out of business in May.

The study’s sole author, Richard Hoover of NASA’s Marshall Space Flight Center in Huntsville, Ala., describes filament-shaped structures he found in freshly fractured slices of the Ivuna, Orgueil and Alais meteorites. He concludes that these structures resemble the remains of single-celled cyanobacteria, which live in water and convert sunlight into food. According to the study, his chemical analysis suggests that the putative fossils are most likely from bacteria that grew while in space rather than terrestrial contaminants that infiltrated the rocks after they fell to Earth.

Hoover did not return phone calls and e-mails, but other scientists had plenty to say. Astrobiologist David Des Marais of NASA’s Ames Research Center in Mountain View, Calif., notes that the microscopic filaments that Hoover imaged aren’t necessarily from bacteria and in fact resemble non-biological structures found in meteorites by other researchers.

The Alais meteorite fell to Earth in 1806 and Orgueil landed in 1864, so both of these rocks had plenty of time to be exposed to terrestrial microbes, notes Chris Chyba of Princeton University. Hoover “obviously thinks he's been able to exclude this, but the threshold to be convincing on this score must be very high, simply on the grounds of the usual ‘extraordinary claims requires extraordinary evidence’ criterion,” Chyba says.

Des Marais’ NASA Ames colleague, astrobiologist Chris McKay, is more positive about the study. Hoover “is a careful and accomplished microscopist so there is every reason to believe that the structures he sees are present and are not due to contamination,” McKay notes. “If these structures had been reported from sediments from a lake bottom there would be no question that they were classified correctly as biological remains.”

McKay says there are two possible explanations for Hoover’s observations. The shapes may have been formed by chance physical or chemical events and are not biological in origin. Or, the material is truly biological in origin and the microenvironments within space rocks are, or were, radically different from what scientists expect. Asteroids, the parent bodies of meteorites, may carry liquid water in their interior, but they wouldn’t be exposed to sunlight or be likely to have the high oxygen concentrations that cyanobacteria would require, McKay says.

He notes that the case Hoover makes is similar to the one made in 1996 by NASA scientists who claimed to have found microfossils in the Martian meteorite ALH84001 (SN: 3/10/01, p. 150). That study, reported in Science, has since been widely disputed.

Then there’s the nature of the journal in which Hoover decided to publish.

During its brief existence, the journal has published such articles as the consequences of human sexual relations on Mars. Its astrobiology editor is N. Chandra Wickramasinghe of Cardiff University in Wales, a vocal advocate for the controversial theory that life on Earth was seeded from space.

NASA, in the meantime, has officially remained mum on the research. “We won’t comment on research that hasn’t gone through peer review,” said Ed Weiler, NASA’s associate administrator for science in Washington, D.C.