Researchers have found oldest fossils in Australia giving a convincing evidence that cells and microscopic organisms like bacteria were able to live in an oxygen free environment 3.4 billion years ago.
The cells and organisms of that time are thought to live on sulfur i.e. they probably used sulfur in place of oxygen for production of energy and the same idea is placed behind the life on other planets in Universe i.e. use of energy sources other than oxygen.
The microfossils, for generating this idea, were found in Strelley Pool, an area in western Australia. These tiny fossils were found preserved among the quartz sand grains of one of the oldest shorelines in world and are found to be about 200 million years old.
The sky was probably grey and cloudy at that time resulting in more heat than today, the oceans were at about 40-50 C and there was very little oxygen.
This study suggested that life on Mars is most probable.
Professor Martin D. Brasier, Department of Earth Sciences, University of Oxford, South Parks Road, Oxford said:
Could these sorts of things exist on Mars? It’s just about conceivable. But it would need these approaches mapping the chemistry of any microfossils in fine detail and convincing three-dimensional images to support any evidence for life on Mars.
References and Further Reading:
Wacey, D. et. al. (2011). Microfossils of sulphur-metabolizing cells in 3.4-billion-year-old rocks of Western Australia. Nature Geoscience.