Oldest signs of life probed in the Pilbara

By Alex Wallace 14 November 2013
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Evidence of what might be the oldest bacteria on Earth could help us find life on other planets, experts say.

SIGNS OF EARLY LIFE discovered in the Pilbara could hold clues to discovering life on other planets, new research suggests.

Rocks studied in the Pilbara region of Australia’s north-west have revealed evidence of complex bacterial communities that existed as far back as 3.48 billion years ago. Thes are in the form of shapes and marks which the researchers believe are prehistoric microbial mats.

Dr David Wacey, a researcher at the University of Western Australia in Perth, was part of a team who published the findings in the journal Astrobiology last week. 

David says that while there have been indications of life in these rocks dated at 3.5 billion years old, the new research verifies the existence of ancient bacteria in these sedimentary formations.

“This is possibly the oldest evidence for life on our planet,” David told Australian Geographic.

Pilbara rocks oldest on Earth

The Pilbara region is home to the oldest and most well-preserved sedimentary rocks on Earth.

“Most rocks of this age [on Earth] have long since disappeared underground, or have been built into mountains and eroded,” David says. “But this area has not been deformed at all for over 3 billion years. It’s quite amazing.”

“We knew the ages of the rocks, and where people had seen other sedimentary rocks here in the past,” he says. “After that, it was a case of getting down on our hands and knees and examining them.”

The fossilised evidence were the result of the interaction of bacteria with the sediment in which they lived. These particular examples of ancient bacterial ecosystems are unique in their complexity.

“It shows that life was abundant and that it had organised itself into communities that appear to have worked together to colonise preferred habitats and protect those habitats from changes such as erosion,” David says.

Life on other planets

David says it is possible that information like this could assist in the discovery of life on other planets, such as Mars.

“Essentially, any new discovery of signs of life of this great age gives us new information about the sorts of environments and rock types we should be targeting when looking for primitive life on other planets,” he says.

While the discovery seems significant, Professor Malcolm Walter, founder of the Australian Centre for Astrobiology, advises a degree of skepticism.

“Interpreting the earliest geological history of life is fraught with difficulties,” Malcolm says.

“The kind of evidence reported here is difficult to interpret. No cells are preserved, which is not surprising, but this, and the style of preservation of the structures, make it very difficult to arrive at convincing interpretations,” he says. 

Structures in the Pilbara rocks interpreted as fragments of fossilised microbial mats. (Credit: Nora Noffke)