A NASA scientist reports detecting tiny fossilised bacteria on three meteorites, and maintains these microscopic life forms are not native to Earth.
If confirmed, this research would suggest life in the universe is widespread and life on Earth may have come from elsewhere in the solar system, riding to our planet on space rocks like comets, moons and other astral bodies.
The study, published online in The Journal of Cosmology, is considered so controversial it is accompanied by a statement from the journal's editor seeking other scientific comment.
The central claim of the study by astrobiologist Richard Hoover is that there is evidence of microfossils similar to cyanobacteria - blue-green algae, also known as pond scum - on the freshly fractured inner surfaces of three meteorites.
These microscopic structures had lots of carbon, a marker for Earth-type life, and almost no nitrogen, says Hoover.
He says nitrogen can also be a sign of Earthly life, but the lack of it only means that whatever nitrogen was in these structures has decomposed out into a gaseous form long ago.
"We have known for a long time that there were very interesting biomarkers in carbonaceous meteorites and the detection of structures that are very similar ... to known terrestrial cyanobacteria is interesting in that it indicates that life is not restricted to the planet Earth," says Hoover.
Hoover, based at NASA's Marshall Space Flight Center in Alabama, has specialised in the study of microscopic lifeforms that survive extreme environments such as glaciers, permafrost and geysers.
Not the first time
He is not the first to claim discovery of microscopic life from other worlds.
In 1996, NASA scientists presented research indicating a 4-billion-year-old meteorite found in Antarctica carried evidence of fossilized microbial life from Mars.
The initial discovery of the so-called Mars meteorite was greeted with acclaim and the rock unveiled at a standing room-only briefing at NASA headquarters in Washington.
Since then, however, criticism has surrounded that discovery and conclusive proof has been elusive.
Hoover's research may well meet the same fate. In a statement published with the online paper, the Journal of Cosmology's editor in chief, Rudy Schild, said in a statement:
"Dr Richard Hoover is a highly respected scientist and astrobiologist with a prestigious record of accomplishment at NASA. Given the controversial nature of his discovery, we have invited 100 experts and have issued a general invitation to over 5000 scientists from the scientific community to review the paper and to offer their critical analysis."
But another NASA researcher has greeted the paper's claims with scepticism.
"Many scientists have examined thousands of meteorites in detail over the past 50 years without finding any evidence of fossil life," David Morrison, senior scientist at the NASA Astrobiology Institute at Ames Research Centre, said in an email to MSNBC.
"Further, we know a great deal about the conditions on the parent objects of the meteorites, which (not counting the few meteorites from the moon and Mars) were rather small, not at all like planets.
"I would therefore invoke Carl Sagan's famous advice that extraordinary claims require extraordinary evidence.
"At a bare minimum this would require publication in a prestigious peer-refereed scientific journal - which this is not. Cyanobacteria on a small airless world sounds like a joke. Perhaps the publication came out too soon; more appropriate would have been on April 1."