Scientists believe they found evidence of microbes thriving near hydrothermal vents on Earth’s surface just 300 million years after the planet formed – the strongest evidence yet that life began much earlier than is widely assumed.
If confirmed, it indicates that the conditions necessary for the emergence of life are relatively basic.
“If life is relatively quick to emerge, under the right conditions, this increases the chance of life on other planets,” said Dominic Papineau, of University College London, who led the research.
Five years ago, Papineau and his colleagues announced that they had found it microfossils In iron-rich sedimentary rocks from the Nuvvuagittuq supracrustal belt in Quebec, Canada. The team suggested that these tiny filaments, knobs, and tubes of an iron oxide called hematite could have been made by bacteria that live around hydrothermal vents that use iron-based chemical reactions to get their energy.
Scientific dating of the rocks indicates that they are at least 3.75 billion years old, and may be as old as 4.28 billion years, which is the age of the igneous rocks in which they were incorporated. Prior to this, the oldest reported microfossils dated to 3.46 billion and 3.7 billion. Years ago, the Canadian specimens were likely the oldest direct evidence of life on Earth.
Now, further analysis of the rock has revealed a larger and more complex structure — a trunk with parallel branches on one side about a centimeter long — as well as hundreds of deformed balls, or ellipsoids, along with tubes and filaments.
“One thing that I think is amazing is the sheer size of the tectonic branching structure, which is several millimeters, if not more than a centimeter in size,” said Babino, adding that it bears some resemblance to filaments made by Mariprofundus ferrooxydans, a modern bacteria found in iron-rich deep-sea environments, particularly hydrothermal vents. “But our country is much bigger, much thicker,” he said.
“I think what we’re seeing is a microbial community — that they were working in concert, and as the filaments grew out of groups of these cells, they mixed and made bigger and thicker hematite filaments.
The team also identified mineral chemical byproducts in the rocks, consistent with these ancient microbes that subsisted on iron, sulfur, and possibly also carbon dioxide and light through a form of oxygen-free photosynthesis.
Taken together, these new discoveries could indicate that a diverse group of microbial life may have existed 300 million years after the formation of the Earth.
“I think it makes sense that it would be as old as the igneous rocks that contained it, which would be 4.28 billion years old,” Papineau said. “Turning back the clock is very important, because it tells us that it takes a very short time for life to appear on the surface of the planet. Very quickly after [Earth formed] There was microbial life going on, eating the iron and sulfur in these hydrothermal vents.”
However, not everyone is convinced that structures are biological in origin. While they bear some similarities to other ancient and modern examples of bacteria, “these comparisons are found in rocks or environments that have not undergone a very high degree of transformation.” [a process involving extreme temperature and pressure] Professor Francis Westall, an expert on ancient fossil bacteria at the French National Center for Scientific Research.
She said, “I am particularly concerned about the parallelism between the strands – they seem to follow the crystal lattices of the host mineral. This is not a germ feature, so the filaments could be a mutant artifact.”
On the other hand, the sulfur signature identified by the team may have a biological origin. “If the sulfur isotope data are correct, it is possible that the chemical deposits represented by Nuvvuagittuq jasperite have hosted traces of life associated with hydrothermal vents,” said Westall.
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