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Preconditions for life already 3.5 billion years ago

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 which could serve as nutrients for microbial life already existed at this time. 

Preconditions for life already 3.5 billion years ago
Gas-rich fluid inclusions containing CO2 (carbon dioxide) and CH4 (methane) were trapped
in host minerals (here quartz) during crystal growth [Credit: Volker Lueders, GFZ]

The study by first author Helge Mißbach (University of Gottingen, Germany) was published in the journal Nature Communications. Co-author Volker Luders from the GFZ German Research Center for Geosciences carried out carbon isotope analyses on gases in fluid inclusions.

Fluid inclusions show potential for prehistoric life

Luders 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 Luders.

Australian barites as geo-archives

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. This includes the pressure, temperature and the solution composition. 

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. The fluid inclusions investigated in this study originate from the Dresser Mine in Australia. They were trapped during crystallisation of the host minerals of barium sulphate (barite). The research team analysed them extensively for their formation conditions, biosignatures and carbon isotopes.

In the course of the analyses, it turned out that they contained primordial metabolism - and thus energy sources for life. The results of Luders' 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," Luders 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. Luders 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."

Source: Helmholtz Association of German Research Centres [March 31, 2021]

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1 comment :

  1. Recent research on the origins and types of life forms on the early earth might logically be extrapolated in considering extraterrestrial life elsewhere in the galaxy. For instance, we might consider that life forms at a basic microscopic or primitive level can be almost assumed to be ubiquitous for earthlike planets, or even planets that have only a few earthlike characteristics (such as Europa).These types of organisms are perhaps more simply and basically evolved than creatures like us, whose entire existence, for instance, may have depended on the chance appearance of a giant rock in space which ended the Mesozoic at just the right time, such that earth didn't end up with velociraptors rather than Homo Sapiens pushing shopping carts around Walmart. The appearance of simple bacteria on a rocky planet in Alpha Centauri, for instance, may be more reliably predictable on a basic level of biological evolution, rather than more complex and more particularized evolved life forms like us. Another theme of modern evolutionary research on earth, the ubiquity of evolutionary convergence as seen, for instance, in animals like marsupial lions or Tasmanian tigers independently evolved on separated continents compared with their ordinary placental mammalian counterparts, might predict the evolution of life forms on other planets given suitable earthlike conditions on planets trillions of miles from earth. That is, evolved alien forms might be recognizable physically and ecologically from their counterparts on earth, made of the same DNA and evolved in similar conditions to what is encountered here despite the spatial separation. The question of life evolving from Martian origins addresses this last possibility even more directly. If earth was seeded by primitive forms from another planet like Mars, then why shouldn't evolutionary convergence between earthlike planets in separate star systems be similarly possible?


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