AFP, Paris
The oldest fossils ever found are "direct evidence" of life on Earth 3.8 to 4.3 billion years ago when our planet was still in its infancy, researchers reported yesterday.
Even at the lower end of the spectrum, "the microfossils we discovered are about 300 million years older" than any runners-up, said Dominic Papineau, a professor at University College London who made the discovery.
The dating puts the fossils "within a few hundred million years of the accretion of the solar system," he said in a video statement.
The results were published in the peer-reviewed journal Nature.
The fact that life kick-started not long after Earth formed suggests it could also emerge on watery worlds outside our Solar System at comparable stages of formation, the scientists said.
"If life happened so quickly on Earth, then could we expect it to be a simple process that could start on other planets?", asked lead author Matthew Dodd, a graduate student at the London Centre for Nanotechnology.
Earth and Mars had liquid water on their surfaces at the same time, he noted.
"We could expect to find evidence for past life on Mars four billion years ago," Dodd said.
It may also be true, he added, that Earth was "just a special case."
The tiny fossils -- half the width of a human hair and up to half-a-millimetre in length -- take the form of blood-red tubes and filaments formed by ocean-dwelling bacteria that fed on iron.
Locked inside white, flower-like quartz structures known to harbour fossils, they were found along what were once warm-water vents on the ocean floor, most often in deep waters.
ron-carbonate (white) rosette with concentric layers of quartz inclusions (grey) and a core of a single quartz crystal with tiny (nanoscopic) inclusions of red hematite from the Nuvvuagittuq Supracrustal Belt are seen in Québec, Canada. Photo: AFP
Such iron-rich, hydrothermal systems exist today, and are home to bacteria that may be similar to those unearthed by Dodd and his colleagues.
Known as the Nuvvuagittuq Supracrustal Belt, the site of the discovery contains some of the oldest sedimentary rocks known on Earth.
Strong evidence of life
They formed between 3.77 and 4.29 billion years ago, and may have been the habitat for the planet's first life forms.
It is still not known when, or where, life on Earth began, but these deep-sea vents are seen as a good candidate.
Earth is thought to be about 4.57 billion years old.
Previous claims of super-ancient fossils have been challenged by scientists asking whether they are, in fact, natural mineral formations of some kind.
"One of the big questions when it comes to early life studies is whether or not the organic carbon we find in these rocks is actually biological in origin," explained Dodd.
The researchers used several methods to check, including laser-imaging to analyse the minerals associated with the organic material.
The presence of two in particular -- apatite and carbonite -- provide strong evidence for life, they said.
Moreover, the flower-like quartz structures in which the tubes and filaments are embedded have often been found in younger rock to contain traces of bacteria that consumed iron for energy.
The possibility that the microfossils were forged by temperature and pressure changes as the sediment formed were also examined, and excluded.
The new fossil find complements the recent discovery of 3.7-million year geological structures in Greenland called stromatolites.
While not fossils, stromatolites are made by microbial colonies, and form in the sunlit surface waters of the ocean.
The oldest microfossils previously reported were found in Western Australia and dated to 3.46 billion years ago, though some scientists say that these are not biological in origin.
Several other research institutions contributed to the new study, including the Geological Survey of Norway, the US Geological Survey, and the University of Ottawa.
Fossil ‘mother lode’ records Earth-shaking asteroid’s impact: study
Researchers believe the impact set off fast-moving, seismic surges that triggered a sudden, massive torrent of water and debris from an arm of an inland sea known as the Western Interior Seaway
WASHINGTON: Scientists in the US say they have discovered the fossilized remains of a mass of creatures that died minutes after a huge asteroid slammed into the Earth 66 million years ago, sealing the fate of the dinosaurs.
In a paper to be published Monday, a team of paleontologists headquartered at the University of Kansas say they found a “mother lode of exquisitely preserved animal and fish fossils” in what is now North Dakota.
The asteroid’s impact in what is now Mexico was the most cataclysmic event ever known to befall Earth, eradicating 75 percent of the planet’s animal and plant species, extinguishing the dinosaurs and paving the way for the rise of humans.
Researchers believe the impact set off fast-moving, seismic surges that triggered a sudden, massive torrent of water and debris from an arm of an inland sea known as the Western Interior Seaway.
At the Tanis site in North Dakota’s Hell Creek Formation, the surge left “a tangled mass of freshwater fish, terrestrial vertebrates, trees, branches, logs, marine ammonites and other marine creatures,” according to Robert DePalma, the report’s lead author.
Some of the fish fossils were found to have inhaled “ejecta” associated with the Chicxulub event, suggesting seismic surges reached North Dakota within “tens of minutes,” he said.
“The sedimentation happened so quickly everything is preserved in three dimensions — they’re not crushed,” said co-author David Burnham.
“It’s like an avalanche that collapses almost like a liquid, then sets like concrete. They were killed pretty suddenly because of the violence of that water. We have one fish that hit a tree and was broken in half.”
The fossils at Tanis include what were believed to be several newly identified fish species, and others that were “the best examples of their kind,” said DePalma, a graduate student and curator of the Palm Beach Museum of Natural History in Florida.
“We look at moment-by-moment records of one of the most notable impact events in Earth’s history. No other site has a record quite like that,” he said.
“And this particular event is tied directly to all of us — to every mammal on Earth, in fact. Because this is essentially where we inherited the planet. Nothing was the same after that impact. It became a planet of mammals rather than a planet of dinosaurs.”
The paper is to be published in the Proceedings of the Academy of Natural Sciences.
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