The earliest evidence for lifeforms on Earth date back as far as 4.3 billion years, in what was once the seabed in Quebec, Canada. It was thought that life took another billion years or more to adapt to land, but new fossils discovered in Western Australia may shake up the timeline a bit. Evidence of microbial life has been found in a layer of rock from a 3.48 billion-year-old hot spring, meaning life took to land some 580 million years earlier than previously thought.
Warm and bubbling with vital minerals, deep sea hydrothermal vents are often thought to be the earliest places on Earth that could harbor life. Fossilized stromatolites, formed by blue-green algae colonies, suggest life sprung up in these areas between 4.3 billion and 3.7 billion years ago. But another theory suggests that hot springs could provide similar conditions away from the sea, and life may have taken off in that environment instead.
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In the Pilbara region in Western Australia, researchers from the University of New South Wales have discovered fossilized evidence of microbes dating back almost 3.5 billion years. Stromatolites, bubbles and certain textures that indicate life were found in a layer of geyserite, a mineral formed under conditions only met in terrestrial hot springs. Before now, the oldest known geyserite was a mere 400 million years old, making the find far older than any other hot spring- or land-based life.
"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," says Tara Djokic, first author of the study. "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."
The implications of the find aren't limited to the history of life on our own planet. Similar ancient hot springs have been detected on Mars, and they are about the same age as those in the Pilbara, which gives future missions to the Red Planet a potentially promising new target in the hunt for extraterrestrial life.
"Of the top three potential landing sites for the Mars 2020 rover, Columbia Hills is indicated as a hot spring environment," says Djokic. "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."
The research was published in the journal Nature Communications.
Source: University of New South WalesView gallery - 3 images