Scientists discover microbial remains in ancient rocks

UNSW scientists have discovered that the famous stromatolites dating back 3.5 billion years of Western Australia contain some of the oldest microbial remains of life on Earth.

Scientists have discovered exceptionally preserved microbial remains in some of the oldest rocks on Earth in Western Australia – a major breakthrough in the field, which offers clues to the origin of life on Earth.

UNSW researchers have discovered the organic matter contained in stromatolites – fossilized microbial structures – from the former Dresser Formation in the Pilbara region of Western Australia.

Stromatolites are of biogenic origin since their discovery in the 1980s. However, despite strong textural evidence, this theory has not been proven for nearly 40 years because scientists have not been able to demonstrate the presence of remains of preserved organic matter – until the publication of today Geology.

"This is an exciting discovery – for the first time we can show the world that these stromatolites are irrefutable evidence of the first life on Earth," says lead researcher Raphael Baumgartner, Associate Researcher at the Australian Center. for Astrobiology in the team of Professor Martin Van Kranendonk at UNSW.

According to Professor Van Kranendonk, this discovery is the closest the team has made to a "smoking gun" to prove the existence of such an ancient life.

"This represents a major advance in our knowledge of these rocks, in the science of life investigations in general and, more specifically, in the search for life on Mars.We now have a new target and a new methodology to search for traces of old life, "says Professor Van Kranendonk.

Deep drilling, looking closely

Since the formation of Dresser was discovered in the 1980s, scientists wondered if these structures were truly microbial and therefore the first signs of life.

"Unfortunately, there is a climate of mistrust of textural biosignatures in the world of research, so the origin of stromatolites in Dresser's training has been hotly debated," said Dr. Baumgartner.

"In this study, I spent a lot of time in the lab, using micro-analysis techniques to look very closely at the rock samples, to prove our theory once and for all."

The stromatolites of the Dresser formation usually come from the surface of the rock and are therefore very altered. For this study, scientists worked with samples taken deeper into the rock, under the weathering profile, where stromatolites are exceptionally well preserved.

"Examining drill core samples allowed us to visualize a perfect snapshot of ancient microbial life," says Dr. Baumgartner.

Using various advanced micro-analysis tools and techniques, including high power electron microscopy, spectroscopy and isotopic analysis, Dr. Baumgartner analyzed the rocks.

He discovered that stromatolites are essentially composed of pyrite – a mineral also called "mad gold" – which contains organic matter.

"The organic matter we found preserved in stromatolite pyrite is exciting, we are looking at cohesive filaments and exceptionally preserved filaments that are typically remnants of microbial biofilms," says Dr. Baumgartner.

The researchers say that such remains had never been seen before in Dresser's training and that having seen the evidence under the microscope was incredibly exciting.

"I was quite surprised, we never expected to find this level of evidence before starting this project.I remember the night under the electron microscope where I finally discovered that I was looking at the remains of biofilm.I think it was around 11 pm, had this moment "eureka", and I stayed until three or four in the morning, just for imaging and imaging because I I was so excited, I completely lost track of time, "says Dr. Baumgartner.

Indices of the search for life on Mars

A little over two years ago, Ms. Baumgartner's colleague, Tara Djokic, Ph.D. candidate of the UNSW, found stromatolites in hot-spring deposits in the same region of the country. Western Australia, repelling 580 million years the oldest known existence of microbial life on Earth.

"Tara's main discoveries have been these exceptional deposits of geyserite that indicate that there have been geysers in this area, and consequently expulsions of fluid on an exposed surface," said Dr. Baumgartner.

"His study focused on the broader geological setting of the paleo-environment – providing support for the theory that life began on earth rather than in the ocean – while my study has really deepened the finer details of the stromatolite structures of the region. "

Scientists say the two studies help us answer a central question: where does humanity come from?

"Understanding where life might have emerged is really important to understanding our ancestry, and from there it could help us understand where life could have happened, for example, where it was started on others. planets, "said Dr. Baumgartner. said.

Last month, scientists from NASA and the European Space Agency (ESA) spent a week in the Pilbara with Martin Van Kranendonk for specialized training in identifying signs of life in these same rocks old. This was the first time that Van Kranendonk shared knowledge of the region with a dedicated team of Mars specialists, a group comprising NASA's mission chiefs and ESA's Mars 2020.

"It is deeply gratifying that the ancient Australian rocks and our scientific know-how are making such a significant contribution to our search for extra-terrestrial life and the discovery of the secrets of Mars," said Professor Van Kranendonk.