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Life on Mars? Fossil find shows it's possible

Scientists have found Earth's oldest fossils in Australia and say their microscopic discovery is convincing evidence that cells and bacteria were able to thrive in an oxygen-free world more than 3.4 billion years ago.
Image: Tubular microfossils
Hand out picture released by journal Nature Geoscience of a collection of tubular microfossils (resembling the protective sheaths of modern bacteria) found in between sand grains in a 3.4 billion-year-old sandstone from Western Australia.David Wacey / AFP / Getty Images
/ Source: Reuters

Scientists have found Earth's oldest fossils in Australia and say their microscopic discovery is convincing evidence that cells and bacteria were able to thrive in an oxygen-free world more than 3.4 billion years ago.

The finding suggests early life was sulphur-based — living off and metabolizing sulphur rather than oxygen for energy — and supports the idea that similar life forms could exist on other planets where oxygen levels are low or non-existent.

===ATTENTION - EMBARGO, RELEASABLE AUGUST 21 at 17.00 GMT - THIS RESTRICTION APPLIES TO ALL MEDIA, INCLUDING WEBSITES=== RESTRICTED TO EDITORIAL USE - MANDATORY CREDIT \"AFP PHOTO / NATURE/ DAVID WACEY \" - NO MARKETING NO ADVERTISING CAMPAIGNS - DISTRIBUTED AS A SERVICE TO CLIENTS – NO ARCHIVE Hand out picture released by journal Nature Geoscience of Strelley Pool in the remote Pilbara region of Western Australia. According to a study published in \"Nature Geoscience\" on August 21, 2011, microfossils were discovered in a 3.4 billion-year-old sandstone at the base of these prominent ridges, confirming that bacteries were living then without oxygen, and making the fossils the oldest ones found on earth. AFP PHOTO NATURE / DAVID WACEY (Photo credit should read David Wacey/AFP/Getty Images)David Wacey / AFP

"Could these sorts of things exist on Mars? It's just about conceivable. This evidence is certainly encouraging and lack of oxygen on Mars is not a problem," said Martin Brasier of Oxford University, who worked on the team that made the discovery.

The microfossils, which the researchers say are very clearly preserved and show precise cell-like structures, were found in a remote part of western Australia called Strelley Pool.

In a study published in the journal Nature Geoscience on Sunday, Brasier's team explained that the tiny fossils were preserved between the quartz sand grains of the oldest shoreline known on Earth in some of the oldest sedimentary rocks ever discovered.

"We can be very sure about the age as the rocks were formed between two volcanic successions that narrow the possible age down to a few tens of millions of years," he said. "That's very accurate indeed when the rocks are 3.4 billion years old."

By analyzing the fossils, the rocks they were found in and the surrounding environment, the scientists have built a picture of Earth at this time as a hot, murky, violent place where there was a high and constant threat of volcanic eruptions and meteor strikes.

===ATTENTION - EMBARGO, RELEASABLE AUGUST 21 at 17.00 GMT - THIS RESTRICTION APPLIES TO ALL MEDIA, INCLUDING WEBSITES=== RESTRICTED TO EDITORIAL USE - MANDATORY CREDIT \"AFP PHOTO / NATURE/ DAVID WACEY-DEREK GERTSMANN \" - NO MARKETING NO ADVERTISING CAMPAIGNS - DISTRIBUTED AS A SERVICE TO CLIENTS – NO ARCHIVE Hand out picture released by journal Nature Geoscience of a 3D reconstruction of a 3.4 billion-year-old microfossil about 10 micrometers in diameter from Western Australia (left). Cross sections through the reconstruction (right) emphasize the spheroidal nature of this ancient cell. According to a study published in \"Nature Geoscience\" on August 21, 2011, microfossils were discovered in a 3.4 billion-year-old sandstone at the base of of Strelley Pool in the remote Pilbara region of Western Australia, confirming that bacteries were living then without oxygen, and making the fossils the oldest ones found on earth. AFP PHOTO NATURE / DAVID WACEY-DEREK GERTSMDavid Wacey-Derek Gertsmann / AFP

The sky would have been cloudy and grey, keeping the heat in even though the sun would have been weaker than today, and the oceans would have been around 40-50 degrees Celsius — the temperature of a hot bath.

Most significantly, there was very little oxygen around since there were no plants or algae to photosynthesize and produce it, Brasier explained in a telephone interview.

"It's a rather hellish picture," he said. "Not a great place for the likes of us. But for bacteria, all of this was wonderful. In fact, if you were to invent a place where you wanted life to emerge, the early Earth is exactly right."

The researchers are now using the techniques and approaches they used in this study to re-examine other fossil finds that scientists have suggested may also contain evidence for very early life on Earth.