Earth's oldest fossils discovered
Source: Agencies |
August 23, 2011, Tuesday
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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.
"Could these things exist on Mars? It's just about conceivable. This evidence is encouraging and the 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, 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."
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.
The sky would have been cloudy and grey, keeping the heat in and the oceans would have been around 40-50 degrees Celsius - the temperature of a hot bath.
There was very little oxygen around since there were no plants or algae to photosynthesize and produce it, Brasier 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 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.
"Could these things exist on Mars? It's just about conceivable. This evidence is encouraging and the 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, 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."
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.
The sky would have been cloudy and grey, keeping the heat in and the oceans would have been around 40-50 degrees Celsius - the temperature of a hot bath.
There was very little oxygen around since there were no plants or algae to photosynthesize and produce it, Brasier 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."
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