Deposits preserved in 3.48 billion-year-old rocks formed in ancient hot springs in Western Australia provide evidence that microbial life on land originated 580 million years earlier than thought, according to a study.
Besides shedding new light on the origin of life on Earth, the researchers believe that their findings have major implications for the search for life on Mars as well.
Previously, the world's oldest evidence for microbial life on land came from 2.7- 2.9 billion-year-old deposits in South Africa containing organic matter-rich ancient soils.
"Our exciting findings don't just extend back the record of life living in hot springs by three billion years, they indicate that life was inhabiting the land much earlier than previously thought, by up to about 580 million years," said study first author Tara Djokic from the University of New South Wales (UNSW) in Sydney.
"This may have implications for an origin of life in freshwater hot springs on land, rather than the more widely discussed idea that life developed in the ocean and adapted to land later," Djokic said.
Scientists are considering two hypotheses regarding the origin of life. Either that it began in deep sea hydrothermal vents, or alternatively that it began on land in a version of Charles Darwin's "warm little pond."
"The discovery of potential biological signatures in these ancient hot springs in Western Australia provides a geological perspective that may lend weight to a land-based origin of life," Djokic said.
For the study, published in the journal Nature Communications, the researchers studied exceptionally well-preserved deposits which are approximately 3.5 billion years old in the ancient Dresser Formation in the Pilbara Craton of Western Australia.
They interpreted the deposits were formed on land, not in the ocean, by identifying the presence of geyserite – a mineral deposit formed from near boiling temperature silica-rich fluids – that is only found in a terrestrial hot spring environment.
Previously, the oldest known geyserite had been identified from rocks about 400 million years old.
"Our research also has major implications for the search for life on Mars, because the red planet has ancient hot spring deposits of a similar age to the Dresser Formation in the Pilbara," Djokic said.
"Of the top three potential landing sites for the Mars 2020 rover, Columbia Hills is indicated as a hot spring environment. If life can be preserved in hot springs so far back in Earth's history, then there is a good chance it could be preserved in Martian hot springs too," Djokic added.