Researchers have discovered that organic molecules are trapped in rock formations that are very ancient in Australia, revealing what they say is the first detailed evidence of early chemical ingredients. could form the basis of the Earth’s main microbial life forms.
The discovery, made in Pilbara Craton’s 3.5-billion-year-old Dresser Creation in Western Australia, contributes to much research that marks ancient life in this part of the world – which is ‘represents one of only two pristine open deposits of land on Earth dating back to the Archean Eon.
In the last few years, the Dresser Formation’s hydrothermal rock has turned out several signs of what appears to be the earliest known life on land, with scientists finding out “conclusive evidence” of microbial biosignatures dating back to 3.5 billion years ago.
Now, in a new study, researchers in Germany have identified traces of specific chemistry that may have enabled such organisms, finding biologically relevant organic molecules that inside are barite deposits, a mineral formed through various processes, including hydrothermal onions.
“In the field, the barites are directly attached to fossil microbial mats, and they smell like rotten eggs when freshly hatched,” explains geologist Helge Mißbach of the University of Cologne, Germany.
“So we suspected they contained organic matter that could have been nourished for the early life of microbes.”
Barite rock from the shape of the dresser. (Helge Mißbach)
Although scientists have long been thinking about how organic molecules could act as substrates for primval microbes and their metabolic processes, direct evidence to date has largely proved conclusive. accessible.
To investigate, Mißbach and co-researchers studied the internal inclusion of barites from the Dresser Creation, with the chemically stable mineral capable of retaining liquids and gases within the rock for billions of years.
Using a range of methods to analyze the barite samples – including gas-mass chromatography spectrometry, microthermometry, and stable isotope analysis, the researchers found what they describe as “Interesting diversity of organic molecules with known or related metabolic relevance”.
These included the organic acids acetic acid and methanethiol, as well as several gases, including hydrogen sulfide, which may be of biological or mature origin.
(Mißbach et al., Nature Communication, 2021)
Above: Barite Rock, showing a close association with stromatolites.
While it may be impossible to be sure of the exact connections, the proximity of these inclusions within the barite rock and nearby organic assemblages known as stromatolites is a. notes that the old chemicals, once transported within hydrothermal liquids, may have affected primary microphone communities.
“Indeed, many of the compounds found in the barite ite flute infusions would have provided distinct substrates for the sulfur-based and methanogenic-based microbes previously proposed as players in Dresser environment, ”the researchers write in their study.
In addition to chemicals that could be used as nutrients or substrates, other fertilizers found within the inoculum may act as ‘building blocks’ for various re-fertilizers. carbon-based chemical reactions – processes that may have initiated microbial metabolism, by depleting energy sources, such as lipids, that can be broken down by life forms.
“In other words, essential ingredients of methyl thioacetate, a critical agent recommended in life exposure, were available in Dresser environments,” the team explains.
“They may have provided the building blocks for chemoautotrophic carbon sequestration and, therefore, anabolic intake of carbon into biofuels.”
The results are reported in Nature Communication.