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Geologists Question 'Evidence Of Ancient Life' In 3.7 Billion-Year-Old Rocks
The oldest evidence of life on Earth probably isn't found in some 3.7 billion-year-old rocks found in Greenland, despite what a group of scientists claimed [DOI: 10.1038/nature19355] [DX] a couple of years ago. That's according to a new analysis [DOI: 10.1038/s41586-018-0610-4] [DX], published Wednesday in the journal Nature by a different team of experts. This second group examined structures within the rock that were thought in 2016 to have been produced by communities of single-celled microbes that grew up from the bottom of a shallow, salty sea. A three-dimensional look at these structures shows that instead of having a telltale upside-down ice-cream cone shape — the kind produced by microorganisms — they are shaped like a Toblerone candy bar.
"They're stretched-out ridges that extend deeply into the rock," said Joel Hurowitz, a geochemist at Stony Brook University in New York and an author of Wednesday's paper. "That shape is hard to explain as a biological structure and much easier to explain as something that resulted from rocks being squeezed and deformed under tectonic pressures." Asked what the chances were that the structures were created by ancient microbes, astrobiologist Abigail Allwood — of NASA's Jet Propulsion Laboratory and lead author of this second analysis — said: "I don't think there's much chance at all."
[...] All of this is vigorously disputed by the researchers who originally claimed that the Greenland rocks contained the world's oldest fossils. They stand by that claim and say that Allwood and her colleagues based their work on just a cursory, one-day visit to the site. [...] Vickie Bennett, of the Australian National University, added that she found the new study "disappointing" and "unfortunate" in that it "only serves to confuse" the earlier research that she and her colleagues did on these ancient rocks. "Basically they did not look at the same rocks — and the details matter," Bennett told NPR in an email. In her view, the rocks in the current study are a "poor-cousin equivalent to the rocks of our original study" and the new analysis "was not conducted with care."
The article does not address evidence found in Quebec in 2017, dated to between 3.77 and 4.28 billion years ago.
Also at USA Today.
Previously: 3.7 Billion-Year-Old Fossil Found
Earliest Known Evidence for Microbial Life on Land: 3.48 Billion Years Old
Analysis of Microfossils Finds that Microbial Life Existed at Least 3.5 Billion Years Ago - "However, the complexity of the fossilized microbes suggests that life arose much earlier, possibly as far back as 4 billion years ago."
(Score: 2) by bzipitidoo on Saturday October 20 2018, @08:27PM (1 child)
Of the 8 known large planets, plus possibly 2 more big 'uns to be discovered, and over 30 moons and dwarf planets large enough to round out under their own gravity, we know of life on only 1. Admittedly, there's lots we do not know, like how life could be possible on a gas giant planet. Such neglect of that possibility seems a bit strange to me, but then, how would we check for such life? Devise probes that can float in the upper atmosphere for extended periods seems the way to go. And the idea that maybe life also started on Mars but died out when the planet lost most of its water is certainly intriguing. Did not life on Earth first arise in watery habitats, and stay in the oceans for at least a billion years?
But supposing the solar system outside of Earth to be sterile, I'd say that points to fairly low odds for that part of the Drake equation, however quickly life arose on Earth.
(Score: 2) by takyon on Saturday October 20 2018, @09:32PM
Of the 8 known planets in our solar system, only 3 are considered to be in the habitable zone, with the one in the middle being Earth. We haven't ruled out life on Mars, and there are possible bodies of liquid water underneath the Martian surface that we can check. If we can confirm past or present life on Mars, suddenly the equation looks much better.
Other planetary systems, such as TRAPPIST-1, may have more than one planet with surface liquid water [caltech.edu]. Some planetary systems, unlike ours, have a gas giant in the habitable zone. Meaning that moons around them could host life.
We also have a huge blind spot in our solar system: the many subsurface oceans and lakes [wikipedia.org]. It's possible that there is life inside Ceres, Europa, Enceladus, AND Pluto. If we start finding life in these places, then we can begin to reach a conclusion that there is life almost anywhere liquid water can be found. Find exoplanets with surface liquid water, and you may find surface life.
[SIG] 10/28/2017: Soylent Upgrade v14 [soylentnews.org]