In the quest to find the origins of life on Earth, scientists have been endeavoring to locate evidence from as far back in time as they possibly can. The problem lies in the fact that the planet itself is about 4.5 billion years old and, therefore, any rock formation from that far back may not have survived the ravages of time.
Even if scientists were to find rocks that old, the chances are that any signs of fossils may have got erased because of the extreme metamorphosis the rocks have undergone over the eons.
The oldest known verified fossil is 3.5 billion years old while fossil from 3.7 billion-year-old rocks in Greenland was reported by scientists last August but are yet to be verified. They are supposed to be stromatolites (small mounds built by communities of shallow water microorganisms).
According to a new study published this week in the journal “Nature” scientists claim to have found traces of bacteria that may have lived 3.7 billion years ago. The rocks in which they were found can be anywhere between 3.77 and 4.28 billion years old. If indeed, it is the latter, it would make rocks nearly as old as the planet itself.
If the age of the fossil (3.7 billion years) does get verification from the scientific community, it will make it the oldest known fossil known to man and rejuvenate the concept that life got a head start on Earth and maybe elsewhere as well.
The rock samples collected from north-eastern Quebec contain thread-like filaments and cylindrical tubes. While the filaments are about half as wide as the human hair, the cylinder-shaped tubes are marginally thicker and both are made up of a mineral rich in iron.
The bacteria are supposed to have thrived near cracks in the seafloor that expel hot, mineral-rich water into the open ocean – the cracks are called hydrothermal vents. Confirmation of the findings will encourage scientists to study similar ocean vents on other planets in the solar system in the search for extraterrestrial life.
“It’s exciting to find life had managed to get a grip and start to evolve on Earth so quickly after the planets formed,” said Matthew Dodd, a Ph.D. student at Britain’s University College, London, and co-author of the study published in “Nature.” “It gives me high hopes of finding life elsewhere in the universe.”
Geochemist Dominic Papineau, also from Britain’s University College London, who heads the team and is one of the co-authors of the study, as well, says that modern bacteria that consume iron excreted similar filaments.
Comparable filaments and tubes are also seen in “microfossils” found in Norwegian rocks that are much younger than the ones the study claims to have discovered from way back, close to the beginnings of the Earth.
The research team also managed to identify tiny concentric rings resembling “rosettes” which have traces of phosphorus, carbon, calcium and minute granules of graphite, all known to be linked to life in one way or another. According to the explanation given by scientists, the rosettes could be the result of a chemical process that began with rotting bacteria.
However, “rosettes” have been seen before in rocks similar in age but whether their origin is biological or not is a matter of debate.
The bacteria may have possibly existed around the hydrothermal cracks on the seafloor or perhaps in the water near the vents as the rock formations around the fossils suggest. Like the modern bacteria that depend on iron, they “would have literally ‘eaten’ the iron … in the same sense that we eat cake,” forming rust-hued mats similar to the ones seen today, said Papineau.
The fact that the scientists collected a wide variety of evidence gives credence to their claims, believes Christopher House of the Pennsylvania State University, who did not take part in the study. The evidence may not be as defined as the ones seen in less older rocks, but House says that the findings “may be as good as it gets for as old as these rocks are.”
“You have life on Earth at a time when we believe there was liquid water on the surface of Mars, and the atmosphere wouldn’t have been too drastically different,” Dodd says in support of the study. “Maybe there was life on Mars in the past, and we have yet to find it.”