The 3.5 billion year old Australian fossils are indeed the oldest ever discovered

Two hikers observe the rock formations of the Dales Gorge in Karijini National Park in Pilbara, Western Australia.Paul Balfe / Flickr

• Scientists have discovered what they thought were 3.5 billion year old fossils in Western Australia nearly 40 years ago. A new study reveals that these rocks actually contained organic life, making it the oldest fossil ever found.
• The discovery confirms that the Earth was home to microbial organisms 3.5 billion years ago.
• This discovery could help NASA scientists search for similar fossilized life forms on Mars.

• Visit the Business Insider home page for more stories.

In search of the first life on Earth, it can be difficult to tell if you are looking at a real fossil or folds in the rock itself. These doubts have long obscured the discovery, in the 1980s, of fossils dating back to 3.5 billion years ago in the Australian desert, considered the oldest. Now scientists think they have finally solved the problem.

In ancient fossilized rock formations called stromatolites, found in the fossil site of the Dresser Formation of the Pilbara region of western Australia, researchers eventually detected traces of organic matter and described their findings in a new study published by the Geology review.

"This is an exciting discovery, and for the first time we are able to show the world that these stromatolites are irrefutable evidence of the very first life on Earth," said the University of New South Wales geologist. lead author of the new study. Raphael Baumgartner, said in a press release.

Confirm the fossil evidence

In 2016, scientists claimed to have discovered in Greenland fossils dating back 3.7 billion years, which destroyed the record of fossils of Pilbara. Subsequent research has shown that these Greenland fossils were only old rocks and that the crown was returned to Australian fossils.

However, even though the researchers were quite certain that the Pilbara fossils were the real deal, it had not been conclusively proven that they contained signs of life. They had the shape and structure of microbial stromatolites, but no evidence of organic matter proves it.

There is not only a tiara and a belt on which one can read "The oldest fossils". This deeply concerns one of the fundamental questions about our very existence: when and how did life develop on Earth?

So Baumgartner and his team went digging. Not literally, though; they analyzed samples of previously drilled cores in subterranean depths below the point where rocks could have been affected by weather conditions.

This means that these samples have been much better preserved than those of the surface; the researchers described the conservation of the samples as "outstanding".

Stromatolite image of the 3.5 – year – old Dresser Formation in Western Australia. The stromatolites are delimited by pyrite, also called mad gold.UNSW Sydney

The researchers analyzed the samples in thin slices using several techniques, including scanning electron microscopy and transmission electron microscopy; energy dispersive X – ray spectroscopy and Raman spectroscopy; mass spectrometry of secondary ions at the nanoscale; and stable analysis of carbon isotopes.

If this sounds exaggerated, well, it's not really. If any of these leads yielded a positive result and the rest did not, it would mean a much drier field for drawing a conclusion. But things looked good.

Final proof of organic life

The team's analyzes revealed that stromatolites consist mainly of a mineral called pyrite, riddled with nanoscopic pores. And pyrite includes nitrogenous organic materials, as well as strands and filaments of organic matter that closely resemble biofilm residues formed by microbial colonies.

"The organic matter we found preserved in stromatolite pyrite is exciting, we are looking at cohesive filaments and exceptionally preserved filaments that are typically microbial biofilm residues," said Baumgartner.

"I was quite surprised, we never expected to find this level of evidence before starting this project."

Previously, another team of researchers from the University of New South Wales had discovered 3.38 billion-year-old microbes in hot-spring deposits in the Pilbara. Because these deposits are about the same age as the Mars crust, it is thought that they could tell us how to find potential fossils on Mars – all the more so as it is proven that the Red planet also had hot springs.

Indeed, NASA has investigated the Pilbara region to try to detect any geological signatures indicating the presence of stromatolites.

"Understanding where life could have emerged is really important to understanding our ancestry," Baumgartner said. "And from there, it could help us understand where life could have happened – for example, where it was launched on other planets."

Den Originalartikel is a publication of ScienceAlert. Copyright 2019. ScienceAlert auf Twitter Folgen.