Scientists find 3.7 billion-year-old fossils, oldest known

The earliest fossil evidence oflife on Earth has been found in rocks 3.7 billion years old inGreenland, raising chances of life on Mars aeons ago when bothplanets were similarly desolate, scientists said on Wednesday.

The experts found tiny humps, between one and four centimetres(0.4 and1.6 inches) tall, in rocks at Isua in south-west Greenland thatthey said were fossilized groups of microbes similar to ones nowfound in seas from Bermuda to Australia.

If confirmed as fossilized communities of bacteria known asstromatolites rather than a freak natural formation thelumps would pre-date fossils found in Australia as the earliestevidence of life on Earth by 220 million years.

• 'Oldest' fossils reveal life 3.4 billion years ago

"This indicates the Earth was no longer some sort of hell3.7 billion years ago," lead author Allen Nutman, of theUniversity of Wollongong, told Reuters of the findings that werepublished in the journal Nature.

"It was a place where life could flourish."

Earth formed about 4.6 billion years ago and the relativesophistication of stromatolites indicated that life had evolved
quickly after a bombardment by asteroids ended about 4 billionyears ago.

"Stromatolites contain billions of bacteria ... they'remaking the equivalent of apartment complexes," said Martin Van
Kranendonk, a co-author at the University of New South Wales whoidentified the previously oldest fossils, dating from 3.48billion years ago.

At the time stromatolites started growing in gooey masses ona forgotten seabed, the Earth was probably similar to Mars withliquid water at the surface, orbiting a sun that was 30 per centdimmer than today, the scientists said.

Those parallels could be a new spur to study whether Marsonce had life, the authors said.

Mars looks more promising for life

"Suddenly, Mars may look even more promising than before asa potential abode for past life," Abigail Allwood, of the
California Institute of Technology, wrote in a commentary inNature.

The Greenland find was made after a retreat of snow and iceexposed long-hidden rocks. Greenland's government hopes that athaw linked to global warming will have positive spin-offs, suchas exposing more minerals.

Nutman said the main controversy was likely to be that thefossils were in metamorphic rocks, reckoned to have formed underhuge stress with temperatures up to 550 C(1,022F) usually too high to preserve any trace of life.

Still, Van Kranendonk told Reuters that dried-out biologicalmaterial could sometimes survive such a baking, adding he was"absolutely convinced" by the Greenland fossils.

• Oldest fossil land organism identified
• Antarctic permafrost may not be habitable for microbes so is Mars?