Scientists from the University of New South Wales (UNSW) have claimed that the earliest existence of microbial life on land might be 580 million years earlier than it was believed to be. Their finding comes from the discovery of fossils in hot spring deposits in the Pilbara region of Western Australia which are believed to be 3.48 billion year old.
In their study, the scientists said that the the world’s oldest evidence for microbial life on land previously 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 3 billion years, they indicate that life was inhabiting the land much earlier than previously thought, by up to about 580 million years,” said Tara Djokic, a UNSW PhD candidate, who is the study first author.
The study which was undertaken by Tara Djokic and Professors Martin Van Kranendonk, Malcolm Walter and Colin Ward of UNSW, and Professor Kathleen Campbell of the University of Auckland, is published in the journal Nature Communications.
“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.
Regarding the origin of life, the researchers are considering two hypotheses – either that it began in deep sea hydrothermal vents, or 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,” said Djokic.
Djokic said that the research would also have major implications for the search for life on Mars. She said that the the ancient hot spring deposits of the red planet are of a similar age to the Dresser Formation in the Pilbara.
“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,” she said.
The researchers studied “well-preserved deposits” which are believed to be 3.5 billion years old in the ancient Dresser Formation in the Pilbara Craton of Western Australia.
Their interpretation with regards to the formation of the deposits on land was based on the identification of the presence of geyserite. According to the researchers, geyserite is a mineral deposit formed from silica-rich, fluids at near boiling-temperature 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, their study said.
The researchers also discovered stromatolites within the hotspring deposits, which showed signs of early life as well. Stromatolites are layered rock structures created by communities of ancient microbes.
“This shows a diverse variety of life existed in fresh water, on land, very early in Earth’s history,” said Professor Van Kranendonk, Director of the Australian Centre for Astrobiology and head of the UNSW school of Biological, Earth and Environmental Sciences.
“The Pilbara deposits are the same age as much of the crust of Mars, which makes hot spring deposits on the red planet an exciting target for our quest to find fossilised life there,” he added.
Professor Malcolm Walter of UNSW and the founding director of the Australian Centre for Astrobiology said: “The Pilbara provides us with a rich record of early life on Earth and is a key region for developing exploration strategies for Mars to try and answer one of the greatest enigmas in science and philosophy – did life arise more than once in the universe?”
Professor Walter said that there are attempts to gain World Heritage listing for its main fossil sites.