In 3.5 Billion-Year-Old Rocks in Australia, scientists find ingredients for life

 

Image Credit: Helge Mißbach

Organic molecules preserved in remarkably ancient rock formations in Australia have been found by researchers, exposing what they claim is the first detailed evidence of early chemical ingredients that may have underpinned the primordial microbial life-forms of Earth.

The find, made in Western Australia's Pilbara Craton's 3.5 billion-year-old Dresser Formation, adds to a large body of research pointing to ancient life in this part of the world, marking one of only two pristine, uncovered land deposits on Earth dating back to the Archean Eon.

In recent years, with scientists finding "definitive evidence" of microbial bio signatures dating back to 3.5 billion years ago, the hydrothermal rock of the Dresser Formation has thrown up repeated signs of what looks to be the earliest known life on earth.

In a new study, researchers in Germany have now found traces of unique chemistry that may have made it possible for such primordial species to exist, and have identified biologically important organic molecules contained within barite deposits, a mineral produced by different processes, including hydrothermal phenomena.

Barites are directly associated with fossilized microbial mats in the area, and when freshly disturbed, they smell like rotten eggs, explains geobiologist Helge Mißbach of the University of Cologne, Germany.

We therefore hypothesized that they contained organic material that for early microbial life may have served as nutrients.

Barite rock from the Formation of Dresser. (Mißbach's Helge)

While researchers have long speculated how organic molecules can serve as substrates for primitive microbes and their metabolic processes, direct evidence has proven to be largely elusive to date.

To investigate, Mißbach and fellow researchers investigated inclusions from the Dresser Formation inside barites, with the chemically stable mineral able for billions of years to retain fluids and gases within the rock.

The researchers found what they classify as an intriguing diversity of organic molecules with established or inferred metabolic significance using a variety of techniques to examine the barite samples, including gas chromatography-mass spectrometry, micro thermometry, and stable isotope analysis.

In addition to various gases, including hydrogen sulfide that may have had biotic or abiotic origins, the organic compounds acetic acid and methane thiol were among these.

Image Credit: Helge Mißbach

ABOVE:The Barite rock, which suggests a close link with stromatolites.

The near proximity of these inclusions inside the barite rock and adjacent organic accretions called stromatolites, although it may be difficult to be sure of the exact links, indicates that the ancient chemicals, once held within hydrothermal fluids, may have affected primitive microbial communities.

Indeed, in the barite-hosted fluid inclusions, several compounds found... would have provided ideal substrates for the previously proposed sulfur-based and methanogenic microbes as players in the Dresser environment, the researchers write in their report.

Other compounds contained inside the inclusions could have served as 'building blocks' for different carbon-based chemical reactions, in addition to chemicals that may have acted as nutrients or substrates, processes that may have kicked off microbial metabolism by generating energy sources, such as lipids, that could be broken down by life forms.

In other words, in the Dresser setting, essential ingredients of methyl triacetate, a proposed critical agent in the emergence of life, were available, the team explains.

The building blocks for chemoautotrophic carbon fixation and thus anabolic carbon absorption into biomass may have been transmitted by them.