Science Mag reports that the rocks are more than 300 million years older than the most ancient signs of life on Earth—fossilized microbial mats called stromatolites that grew in shallow seas.
A team led by geochemist Dominic Papineau of University College London and his Ph.D. student Matthew Dodd says it has found clear evidence of such ancient vent life. The clues come from ancient rocks in northern Quebec in Canada that are at least 3.77 billion years old and may be even older than 4 billion years.
Last year, scientists reported identifying odd reddish peaks in 3.7-billion-year-old rocks in Greenland that may be the product of stromatolites, though many doubted that interpretation. The best evidence for these fossilized algal mats comes from 3.4-billion-year-old rocks in Australia, generally thought of as the strongest evidence for early life on Earth.
Dodd examined hair-thin slices of rock from this formation and found intriguing features: tiny tubes composed of an iron oxide called hematite, as well as filaments of hematite that branch out and sometimes terminate into large knobs.
“The authors offer a convincing set of observations that could signify life,” says Kurt Konhauser, a geomicrobiologist at the University of Alberta in Edmonton, Canada, who was not involved in the study. But “at present, I do not see a way in which we will definitively prove ancient life at 3.8 billion years ago.”
“It’s a challenge in rocks that have been this messed up,” says Abigail Allwood, a geologist with NASA’s Jet Propulsion Laboratory in Pasadena, California, who was also not involved in the study. “There’s only so much you can do with them.”