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 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 ofOxford 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.