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The recently discovered microfossils, some 3.42 billion years old, are the oldest evidence to date of a particular type of methane-cycling microbial life – and they could help us understand how life begins in first, both on Earth and further afield in the Universe.
These life forms would have originally existed just below the seabed in pockets of a rich liquid soup, created from the mixture of colder seawater from above and hotter hydrothermal fluids rising from the sea. depths.
The new findings may answer some of the questions about how and where life began in the Paleoarchean era (3.2-3.6 billion years ago), or whether native microorganisms like this existed even earlier in Earth’s history.
The outcrop from which a sample was taken. (Cavalazzi et al., Science Advances, 2021)
“We found exceptionally well-preserved evidence of fossilized microbes that appear to have thrived along the walls of cavities created by hot water from hydrothermal systems a few meters below the seabed,” says paleontologist Barbara Cavalazzi of the University of Bologna.
“Subterranean habitats, heated by volcanic activity, likely hosted some of Earth’s earliest microbial ecosystems and this is the oldest example we have found to date.”
The rocks containing the fossils were collected from the Barberton greenstone belt in South Africa, near the border with Eswatini and Mozambique – a place where some of the oldest and best preserved sedimentary rocks on the planet are found. whole.
Analysis of the recovered sediment showed microfossils with a carbon-rich outer coating around a core that was both chemically and structurally distinct – indicating microorganisms with cellular material enveloped in a wall or membrane.
Further study revealed most of the major chemicals needed for life, as well as other supporting evidence that these microfossils were once microbes: concentrations of nickel similar to those found in prokaryotic archaea today. ‘hui, microbes that use methane rather than oxygen like their distant ancestors did. .
“Although we know that prokaryotic archaea can be fossilized, we have extremely limited direct examples,” Cavalazzi explains. “Our findings may extend the record of Archaeal fossils for the first time around the time life first appeared on Earth.”
Scientists continue to make progress in understanding how life on Earth began and how the inorganic turned organic – perhaps with the help of a billion years of lightning strikes or hydrothermal vent blasts – but we still don’t know exactly what happened. and in what order.
This might not be surprising, given how difficult it is to look billions of years back, but this latest research suggests that underground hydrothermal systems could be as important in the creation of life as some scientists did. had already assumed.
Better understanding the conditions life needs to exist and the parameters in which it can function is going to be useful, not only for tracing the origins of life on Earth, but also for researching it on other planets.
“As we also find similar environments on Mars, the study also has implications for astrobiology and the chances of finding life beyond Earth,” says Cavalazzi.
The research was published in Scientists progress.
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