Researchers have discovered organic molecules trapped in incredibly ancient rock formations in Australia, revealing what they say is the first detailed evidence of the first chemical ingredients that could have underpinned the Earth’s primitive microbial life forms.
The discovery, made in the 3.5 billion-year-old Australian dresser of Pilbara Craton Dresser, adds to an important body of research that points to the ancient life of this part of the world, which represents one of the two deposits on display. immaculate earth on Earth dating back to the archaic Aeon.
In recent years, the hydrothermal rock of the Dresser Formation has given repeated signs of what appears to be the oldest known life on earth, with scientists discovering “definitive evidence” of microbial biosignatures dating back 3.5 billion years. of years.
Now, in a new study, researchers in Germany have identified traces of specific chemistry that could have allowed the existence of these primordial organisms, finding biologically relevant organic molecules contained within the deposits of barite, a mineral formed by various processes, including hydrothermal phenomena.
“In the field, barites are directly associated with fossilized microbial mats and smell like rotten eggs when they have just been scratched,” explains geobiologist Helge Mißbach of the University of Cologne in Germany.
“Therefore, we suspected they contained organic material that could have served as nutrients for early microbial life.”
Barite rock of the Dresser formation. (Helge Mißbach)
Although scientists have long formulated the hypothesis about how organic molecules could act as substrates for primitive microbes and their metabolic processes, so far direct testing has been largely elusive.
To investigate, Mißbach and other researchers examined the barite inclusions in the Dresser formation, with the chemically stable mineral capable of preserving fluids and gases inside the rock for billions of years.
Using a number of techniques to analyze barite samples, including gas chromatography, mass spectrometry, microthermometry, and stable isotope analysis, the researchers found what they describe as an “intriguing diversity of organic molecules. with known or inferred metabolic relevance “.
Among these were the organic compounds acetic acid and methanethiol, as well as numerous gases, including hydrogen sulfide, that could have biotic or abiotic origins.
(Mißbach et al., Nature Communications, 2021)
Above: barite rock, which indicates a close association with stromatolites.
While it may be impossible to be sure of precise bonds, the proximity of these inclusions within barite rock and adjacent organic accretions called stromatolites suggests that ancient chemicals, once carried within hydrothermal fluids, may have influenced primitive microbial communities.
“In fact, many compounds discovered in barite-hosted fluid inclusions … would have provided ideal substrates for sulfur-based microbes and methanogens previously proposed as actors in the Dresser environment,” the researchers write in their study.
In addition to chemicals that may have acted as nutrients or substrates, other compounds within the inclusions may have served as “building blocks” for various carbon-based chemical reactions, processes that may have initiated microbial metabolism by producing energy sources, such as lipids, that could be broken down by life forms.
“In other words, the essential ingredients of methyl thioacetate, a proposed critical agent in the emergence of life, were available in Dresser environments,” the team explains.
“They could have transmitted the basics for chemoautotrophic carbon fixation and therefore anabolic carbon sequestration in biomass.”
The findings are reported in Communications on Nature.