Researchers have reported finding structures that appear to show life on Earth dates back 3.7 billion years. The discovery, from some of the Earth's most ancient rocks, might help in the search for life on Mars.
Australian scientists on Thursday reported evidence that life was older than had previously been thought - by hundreds of million of years.
Cauliflower-like fossilized structures dating back 3.7 billion years were found preserved in ancient rocks along the edge of the ice cap of Greenland, the scientists said.
The remnants appear to show life emerged a relatively short time after the Earth was formed 4.5 billion years ago, researchers said in the study, which was published in the science journal Nature on Thursday.
"This discovery represents a new benchmark for the oldest preserved evidence of life on Earth," said Professor Martin Julian Van Kranendonk, a geology expert at the University of New South Wales. "It points to a rapid emergence of life on Earth."
The structures, known as stromatolites, were one-to-four centimeters high and were exposed after snow melted away. Stromatolites were described as being "like the house left behind made by microbes," are formed when microorganisms, including certain bacteria, settle with pieces of sediment in layers.
'Green ocean, orange skies'
Scientists used the layers of ash to date the finds back using a standard dating method, Van Kranendonk said.
"It would have been a very different world," he said. "It would have had black continents, a green ocean with orange skies."
The age of the structures is not uncontested, given that they come from some of the most ancient rocks on Earth. Pressure and heat have changed the crystals within, erasing much of the fine-scale detail.
However, the discovery could offer hope that, given the speed at which life appears to have evolved on Earth, there might - at least at one time - have been life on Mars. Future missions to the Red Planet might even seek out Martian stromatolites.
The earliest previous evidence of life on Earth was made in 2006 when Australian and Canadian researchers dated microfossils in rocks in Western Australia at more than 3.4 billion years old.
rc/sms (AFP, AP)