Preconditions for Life Already 3.5 Billion Years Ago (Earth Science)

Microbial life already had the necessary conditions to exist on our planet 3.5 billion years ago. This was the conclusion reached by a research team after studying microscopic fluid inclusions in barium sulfate (barite) from the Dresser Mine in Marble Bar, Australia. In their publication “Ingredients for microbial life preserved in 3.5-billion-year-old fluid inclusions,” the researchers suggest that organic carbon compounds that could serve as nutrients for microbial life already existed at this time. Volker Lüders  from the GFZ German Research Center for Geosciences was also involved in the study by first author Helge Mißbach (University of Göttingen, Germany), which was published in the journal Nature Communications. Lüders carried out carbon isotope analyses on gases in fluid inclusions in the Organic Geochemistry Section.

Fluid inclusions show potential for prehistoric life

Lüders assesses the results as surprising, although he cautions against misinterpreting them. “One should not take the study results as direct evidence for early life,” says the GFZ researcher. Rather, the findings on the 3.5-billion-year-old fluids showed the existence of the potential for just such prehistoric life. Whether life actually arose from it at that time cannot be determined. Based on the results, “we now know a point in time from which we can say it would have been possible,” explains Lüders.

Using a method for simultaneous measurements of isotopes ratios of carbon and nitrogen in small amount of gas, the gases of fluid inclusions can be analyzed © photo: Volker Luders

Australian barites as geo-archives

The research team has analyzed fluid inclusions in Australian barites for formation conditions (pressure, temperature and solution composition), bio signatures, and carbon isotopes. Fluid inclusions in minerals are microscopic geo-archives for the migration of hot solutions and gases in the Earth’s crust. Primary fluid inclusions were formed directly during mineral growth and provide important information about the conditions under which they were formed. In addition to an aqueous phase, fluid inclusions can also contain gases whose chemistry can persist for billions of years. The fluid inclusions examined in this study were trapped during crystallization of the host minerals. In the course of the analyses, it turned out that they contained primordial metabolism – and thus energy sources for life. The results of Lüders’ carbon isotope analysis provided additional evidence for different carbon sources. While the gas-rich inclusions of gray barites contained traces of magmatic carbon, clear evidence of an organic origin of the carbon could be found in the fluid inclusions of black barites.

Follow-up research is possible

“The study may create a big stir,” Lüders says. Organic molecules of this type have not yet been found so far in fluid inclusions in Archean minerals. At the same time, however, he says the study is just a first step. Lüders says, “The ever-increasing sensitivity of measuring instruments will provide new tools for the study of solid and fluid micro inclusions in minerals. Measurements of bio signatures and isotope ratios are likely to become increasingly accurate in the near future.”

Featured image: Gas rich fluid inclusions containing carbon dioxide and methane were trapped in host minerals (here quartz) during crystal growth © Luders, Volker

Original study:
Mißbach, H., Duda, JP., van den Kerkhof, A.M. et al. Ingredients for microbial life preserved in 3.5 billion-year-old fluid inclusions. Nat Commun 12, 1101 (2021).

Provided by GFZ Potsdam

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