Oldest evidence of life on land discovered in Western Australia
Fossils discovered in the Pilbara, Western Australia, have thrown life on land back half a billion years – and offer scientists new clues on where to look for life on Mars.
THE OLDEST FOSSIL evidence of life on land has been discovered in ancient hot spring deposits in the Pilbara, Western Australia. The new evidence could help pave the way for the search for life on Mars.
Published today in Nature Communications, the new findings indicate that life was present on land 580 million years earlier than previously thought. The discovery also extends the record of microbes living in hot springs by 3 billion years.
“It provides a geological perspective to the origins of life,” said Tara Djokic, lead author and PhD candidate at the University of New South Wales’ Australian Centre for Astrobiology.
“Our research lends weight to life originating in hot springs, and not the ocean as widely discussed.”
Ridges in the Dresser Formation in the Pilbara Craton that preserve ancient stromatolites and hot spring deposits. (Credit: Kathleen Campbell)
Before this new discovery in the Pilbara Craton’s Dresser Formation, the world’s oldest fossil evidence of microbial life on land came from 2.7 billion-year-old soil deposits in South Africa.
While the Dresser Formation has been a global hot spot for finding ancient life for the last few decades, it was only recently classified as volcanic in origin.
However, until this work, no one had managed to directly link life with hot springs, which represent the surface features of a volcanic system exposed on land.
After investigating samples from the 3.48 billion-year-old hot spring deposits in the Pilbara, researchers from UNSW found traces of geyserite, a rock type found only in terrestrial hot springs.
“The presence of geyserite in these deposits was the smoking gun that indicated that the volcano originated on land and not in the ocean,” said Tara.
The researchers also found a variety of microbial fossils in the deposits, including stromatolites and gas bubbles preserved in what is suggested as fossilised microbial substance, a feature not found previously in the Dresser Formation.
UNSW PhD student Tara Djokic pointing at 3.48 billion-year-old rocks containing the mineral deposit geyserite and biosignatures in the ancient Dresser Formation in the Pilbara Craton. (Credit: Bruce Damer)
In addition to extending the known record of life on land and in hot springs, Tara said the findings will also be valuable in the search for fossil life on Mars.
“Much of the crust on Mars is around the same age as the hot spring deposits found in the Pilbara, so if life ever developed on the Red Planet we would have a good chance of finding it in the hot springs there too,” said Tara.
Simon George, an organic geochemist from Macquarie University in Sydney, said the new discovery represents an important leap forward that will help scientists figure out where to look for signs of life on Mars.
“This is a highly significant study which demonstrates several lines of evidence that there was life in the 3.48 billion-year-old hot springs,” said Simon, who was not involved in the study.
“This evidence will be used by NASA when it evaluates the three remaining candidate locations for the 2020 Mars Exploration Mission.”