Getting hints from the remainder of 3.4-billion-year-old rocks, a team of geologists have unearthed possibly the oldest known fossils ever, which may unfold the mysteries around the early development of life on Earth.

Not exciting enough? What if the findings could benefit the search for life on Mars?

 

A team led by David Wacey of the University of Western Australia and Martin D. Brasier of the University of Oxford found the cell-like microfossils, 3.4 billion years old, in black sandstone of the Strelley Pool Formation in Western Australia, a beach-turned inland.

According to Sunday's Nature Geoscience where the findings were published, chemical analysis of rocks hints that life was around as long ago as 3.5 billion years, but it is difficult to reach physical evidence due to obstacles in proving that fossils that resemble cells are actually signs of life.

Uncertainties around the fossil structures have deepened the mystery of when life actually emerged.

However, the latest findings should shed light to the researches, says Brasier.

This goes some way to resolving the controversy over the existence of life forms very early in Earth's history. The exciting thing is that it makes one optimistic about looking at early life once again.

The new fossil evidence points to early life using sulfur for energy and  growth, in the absence of oxygen before the photosynthesizing action of green plants and algae began.

The world back then was a harsh environment, often shaken by volcanic activity and the atmosphere was full of methane, causing greenhouse warming to heat the surface to molten rock and boil the oceans into an red-hot mist.

This ability to essentially 'breathe' sulfur compounds has long been thought to be one of the earliest stages in the transition from a non-biological to biological world, said Wacey.

It was pretty incredible, Wacey said of his first encounter with the microfossils preserved in the form of tiny circles and tubes. Martin [Brasier] had seen huge amounts of material and he was tearing his hair out. He thought he would never find anything.

The discovered microfossils are 200 million years older than the next oldest example of fossil microbes found last year.

Researchers are convinced the tiny fossils showing cell-like structures are biological rather than mineral, pointing to their clusters formed in appropriate habitats as well as the chemical make-up of the structures.

 At last we have good solid evidence for life over 3.4 billion years ago, said Brasier. It confirms there were bacteria at this time, living without oxygen.

The authors have demonstrated as robustly as possible, given current techniques and the type of preservation, the biological origin of these microstructures, says Emmanuelle Javaux, a palaeobiologist at the University of Liège in Belgium.

However, she remains cautious, adding, Maybe one day we will come up with a non-biological explanation for this type of microstructure - only time will tell.

The findings may advance forward the search for signs of life on other planets such as Mars or the moons of Jupiter and Saturn. 

Could these sorts of things exist on Mars? It's just about conceivable, said Brasier.

I mean, wow, we now know that sulfur-based metabolism happened very early on Earth. And early Mars had water and sulfur. It shared in many ways the environment of the early Earth, said , David Des Marais, an astrobiologist at the NASA Ames Research Center

This gives us confidence that looking for these types of organisms on Mars is a good strategy.