LONDON: 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 sulfur-based – living off and metabolizing sulfur – and supports the idea that similar life-forms could exist on other planets where oxygen levels are low or non-existent.
“Could these sorts of things exist on Mars? It’s just about conceivable. This evidence is certainly encouraging” 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 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.
By analyzing the fossils, the rocks they were found in and the surrounding environment, the scientists have built a picture of Earth at that time as a hot, murky, violent place where there was a constant threat of volcanic eruptions.
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.”