It was an extraordinary statement: scientists studying a rock formation in Greenland said they had discovered the oldest fossils on Earth, a series of small cone shape left behind by microbial mats some 3.7 billion years ago. The 2016 announcement on the pages of the journal Nature generated global media coverage (including the front page of the Washington Post) and potentially brought a cosmic meaning. These supposed fossils suggested that life appeared on Earth soon after the planet had cooled down enough to be habitable. The implication was that, given the right conditions, life is common, quickly unleashed everywhere in the universe.
A NASA astrobiologist, Abigail Allwood, hoped it was true: it is in a field that has a radical interest in life in the cosmos – but she wanted to look at it for herself. In September 2016, you and your colleagues visited the Greenland site. On Wednesday they published their findings, again in the journal Nature, a complete refutation of the previous study. Allwood and colleagues say that Greenland's facilities do not have a biological origin. They are just rocks.
The "conical" structures previously identified as fossil stromatolites are not really conical, according to the new report. The authors say that they are the cross-section of what is actually a ridge, an elongated structure formed by natural tectonic forces.
"They are not ice cream cones, they are Toblerone bars," said Allwood, who works at NASA's Jet Propulsion Laboratory in Pasadena, California
The lead author of the 2016 paper, Allen Nutman, geologist at the University of Wollongong in Australia, issued a statement saying that he and his co-authors are "bewildered" by Allwood's report and support their previous interpretation. Nutman said that Allwood focused on just one part of Isua, the rock formation of Greenland, a section that he and his colleagues had avoided. He said there was another snow-covered site that had better examples of fossil stromatolites.
"This is a classic that compares the scenario of apples and oranges inevitably leading to our and their observations do not match exactly," wrote Nutman in his statement, which he sent to the Washington Post .
The new report is the latest eruption of litigation in the field of paleobiology, which has long been marked by strong disagreements over what is a true fossil or signature of life and what is only a little of interesting geology. In Western Australia, fossilized stromatolites have been dated about 3.5 billion years ago and are accepted in the scientific community as the oldest known relics of the first years of life on the planet. The field is hampered by the scarcity of such ancient rocks because the Earth's surface has been eroded and reworked over the last billion years.
The age of the Greenland site is not under discussion. It is possible that there are relics of early age in geological formation. But the burden of proof is on Nutman, not on the skeptical scientist who reviewed the site, said Roger Buick, a geologist at the University of Washington who two years ago expressed skepticism about Nutman's original report.
Buick said Nutman's extraordinary claim requires extraordinary evidence. According to Buick, "the evidence should be very strong." This simply is not, and so Allwood et al., The paper is a corrective welcome to something that should never be published in the first instance with such certainty. "
Allwood said he was disappointed that the Greenland structures did not appear to be of biological origin. NASA hopes to find signs of ancient life on Mars and a first appearance of life on Earth would make it more likely. But he said that the moment he arrived at the Greenland site he knew something was wrong.
"The moment we saw the outcrop, we thought, oh, hell, those rocks have been stretched and bent into oblivion.There is no way on Earth that is not deformed" he said.
Recognizes that his speech will not end the debate on what the structures of Greenland mean.
"The way to solve this sort of thing in science is to have a lot of experts, knowledgeable experts, respected experts, go out and look at the rocks and see what they think, otherwise it's a" he said "," he said " , "he said.