Top NASA scientists say there is no scientific evidence to support a colleague's claim that fossils of alien microbes born in outer space had been found in meteorites on Earth.
The US space agency formally distanced itself from the paper by NASA scientist Richard Hoover, whose findings were published on Friday in the peer-reviewed Journal of Cosmology, which is available free online.
"That is a claim that Mr. Hoover has been making for some years," said Carl Pilcher, director of NASA's Astrobiology Institute.
"The science community who analyses meteorites has been aware of these claims for many years," he said.
"I am not aware of any support from other meteorite researchers for this rather extraordinary claim that this evidence of microbes was present in the meteorite before the meteorite arrived on Earth and and was not the result of contamination after the meteorite arrived on Earth."
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Pilcher said the meteorites that Hoover studied fell to Earth 100 to 200 years ago and were heavily handled by humans, "so you would expect to find microbes in these meteorites".
Scientists inside and outside NASA have criticised and even ridiculed Hoover's study, his credentials and the journal itself.
They say that Hoover works in solar physics and doesn't have expertise in astrobiology.
Paul Hertz, chief scientist of NASA's Science Mission Directorate in Washington, also issued a statement saying NASA did not support Hoover's findings.
"While we value the free exchange of ideas, data, and information as part of scientific and technical inquiry, NASA cannot stand behind or support a scientific claim unless it has been peer-reviewed or thoroughly examined by other qualified experts," Hertz said.
"This paper was submitted in 2007 to the International Journal of Astrobiology.
However, the peer review process was not completed for that submission," he added. "NASA also was unaware of the recent submission of the paper to the Journal of Cosmology or of the paper's subsequent publication."
According to the study, Hoover sliced open fragments of several types of carbonaceous chondrite meteorites, which can contain relatively high levels of water and organic materials, and looked inside with a powerful microscope. He found bacteria-like creatures that he calls "indigenous fossils," which he believes originated beyond Earth and were not introduced here after the meteorites landed.
"He concludes these fossilised bacteria are not Earthly contaminants but are the fossilised remains of living organisms which lived in the parent bodies of these meteors, eg. comets, moons, and other astral bodies," said the study.
"The implications are that life is everywhere, and that life on Earth may have come from other planets."
The journal's editor in chief, Rudy Schild of the Center for Astrophysics, Harvard-Smithsonian, said Hoover is a "highly respected scientist and astrobiologist with a prestigious record of accomplishment at NASA".
The publication invited experts to weigh in on Hoover's claim, and sceptics and supporters began publishing their commentaries on the journal's website on Monday. Similar claims about life in a meteorite found in Antarctica were made by other NASA scientists in 1996 and announced by President Bill Clinton on the White House front lawn. But they were not backed up by follow-up research and remain in dispute. Back then, NASA trumpeted the finding, but not so this time.
NASA astrobiologist David Morrison said Hoover's work falls far short of good science. "If Hoover wants to be taken seriously by the community of astrobiologists, he needs to publish this in a real journal and to respond to the criticisms from other scientists," Morrison said in an email and on a NASA web site.
"That is the way science advances."
