Microfossils, believed to be 3.4 billion years old, have been discovered in the Pilbara.
The ABC reports researchers from Western Australia and Britain uncovered the fossils in sandstone at Strelley Pool, west of Marble Bar.
Dr David Wacey says now that scientists know microfossils can be present in sandstone they can start targeting the rock type in future searches.
He says their research also indicates the microbes may have survived on sulfur rather than oxygen.
Dr Wacey says it is a very exciting discovery.
''Any time we find anything like this it gives us more hope for finding similar things on Mars or elsewhere one day, probably quite a while in the future, but it's still quite exciting stuff,'' he said.