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posted by Fnord666 on Saturday October 20 2018, @04:04PM   Printer-friendly [Skip to comment(s)]

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."


Original Submission

Related Stories

3.7 Billion-Year-Old Fossil Found 6 comments

Scientists have found evidence of microbial life in a fossil dated to 3.7 billion years ago:

Rapid emergence of life shown by discovery of 3,700-million-year-old microbial structures (DOI: 10.1038/nature19355) (DX)

Biological activity is a major factor in Earth's chemical cycles, including facilitating CO2 sequestration and providing climate feedbacks. Thus a key question in Earth's evolution is when did life arise and impact hydrosphere–atmosphere–lithosphere chemical cycles? Until now, evidence for the oldest life on Earth focused on debated stable isotopic signatures of 3,800–3,700 million year (Myr)-old metamorphosed sedimentary rocks and minerals from the Isua supracrustal belt (ISB), southwest Greenland. Here we report evidence for ancient life from a newly exposed outcrop of 3,700-Myr-old metacarbonate rocks in the ISB that contain 1–4-cm-high stromatolites—macroscopically layered structures produced by microbial communities. [...] The ISB stromatolites predate by 220 Myr the previous most convincing and generally accepted multidisciplinary evidence for oldest life remains in the 3,480-Myr-old Dresser Formation of the Pilbara Craton, Australia.

Reported at BBC, Ars Technica, and Reuters.


Original Submission

Oldest Evidence of Life on Earth Found in 3.77-4.28 Billion Year Old Fossils 5 comments

Scientists have found fossilized microbes that they have dated to between 3.77 and 4.28 billion years old:

The fossil structures were encased in quartz layers in the so-called Nuvvuagittuq Supracrustal Belt (NSB). The NSB is a chunk of ancient ocean floor. It contains some of the oldest volcanic and sedimentary rocks known to science.

The team looked at sections of rock that were likely laid down in a system of hydrothermal vents - fissures on the seabed from which heated, mineral-rich waters spew up from below. Today, such vents are known to be important habitats for microbes. And Dr Dominic Papineau, also from UCL, who discovered the fossils in Quebec, thinks this kind of setting was very probably also the cradle for lifeforms between 3.77 and 4.28 billion years ago (the upper and lower age estimates for the NSB rocks).

[...] At present, perhaps the oldest acknowledged evidence of life on the planet is found in 3.48-billion-year-old rocks in Western Australia. This material is said to show remnants of stromatolites - mounds of sediment formed of mineral grains glued together by ancient bacteria. An even older claim for stromatolite traces was made in August last year. The team behind that finding said their fossil evidence was 3.70 billion years old. [...] Part of the interest in ancient life is in the implication it has for organisms elsewhere in the Solar System. "These (NTB) organisms come from a time when we believe Mars had liquid water on its surface and a similar atmosphere to Earth at that time," said Mr Dodd. "So, if we have lifeforms originating and evolving on Earth at this time then we may very well have had life beginning on Mars."

Evidence for early life in Earth's oldest hydrothermal vent precipitates (DOI: 10.1038/nature21377) (DX)


Original Submission

Earliest Known Evidence for Microbial Life on Land: 3.48 Billion Years Old 11 comments

http://newsroom.unsw.edu.au/news/science-tech/oldest-evidence-life-land-found-348-billion-year-old-australian-rocks

Fossils discovered by UNSW scientists in 3.48 billion year old hot spring deposits in the Pilbara region of Western Australia have pushed back by 580 million years the earliest known existence of microbial life on land. Previously, the world's oldest evidence for microbial life on land came from 2.7- 2.9 billion-year-old deposits in South Africa containing organic matter-rich ancient soils.

"Our exciting findings don't just extend back the record of life living in hot springs by 3 billion years, they indicate that life was inhabiting the land much earlier than previously thought, by up to about 580 million years," says study first author, UNSW PhD candidate, Tara Djokic. "This may have implications for an origin of life in freshwater hot springs on land, rather than the more widely discussed idea that life developed in the ocean and adapted to land later."

Scientists are considering two hypotheses regarding the origin of life. Either that it began in deep sea hydrothermal vents, or alternatively that it began on land in a version of Charles Darwin's "warm little pond". "The discovery of potential biological signatures in these ancient hot springs in Western Australia provides a geological perspective that may lend weight to a land-based origin of life," says Ms Djokic.

Earliest signs of life on land preserved in ca. 3.5 Ga hot spring deposits (open, DOI: 10.1038/ncomms15263) (DX)

Previously:
3.7 Billion-Year-Old Fossil Found
Oldest Evidence of Life on Earth Found in 3.77-4.28 Billion Year Old Fossils
Researchers Use Genetic Analysis to Determine That Comb Jellies Were the Earliest Animals


Original Submission

Analysis of Microfossils Finds that Microbial Life Existed at Least 3.5 Billion Years Ago 10 comments

According to a new fossil analysis, previously described Australian fossils do contain evidence of 3.5-billion-year-old microbial life. However, the complexity of the fossilized microbes suggests that life arose much earlier, possibly as far back as 4 billion years ago:

In 1992, researchers discovered evidence of what was then potentially the earliest life on Earth: 3.5-billion-year-old microscopic squiggles encased in Australian rocks. Since then, however, scientists have debated whether these imprints truly represent ancient microorganisms, and even if they do, whether they're really that old. Now, a comprehensive analysis of these microfossils suggests that these formations do indeed represent ancient microbes, ones potentially so complex that life on our planet must have originated some 500 million years earlier.

The new work indicates these early microorganisms were surprisingly sophisticated, capable of photosynthesis and of using other chemical processes to get energy, says Birger Rasmussen, a geobiologist at Curtin University in Perth, Australia, who was not involved with the work. The study "will probably touch off a flurry of new research into these rocks as other researchers look for data that either support or disprove this new assertion," adds Alison Olcott Marshall, a geobiologist at the University of Kansas in Lawrence who was not involved in the effort.

[...] The analysis detected several distinct carbon ratios in the material [DOI: 10.1073/pnas.1718063115] [DX], Schopf, Valley, and colleagues report today in the Proceedings of the National Academy of Sciences. Two types of microfossils had the same carbon ratio as modern bacteria that use light to make carbon compounds that fuel their activities—a primitive photosynthesis that did not involve oxygen. Two other types of microfossils had the same carbon ratios as microbes known as archaea that depend on methane as their energy source—and that played a pivotal role in the development of multicellular life. The ratio of a final type of microfossil indicated that this organism produced methane as part of its metabolism.

That there are so many different carbon ratios strengthens the case that these are real fossils, Schopf says. Any inorganic processes that could have created the squiggles would be expected to leave a uniform carbon ratio signature, he says. The fact that microbes were already so diverse at this point in Earth's history also suggests that life on our planet may date back to 4 billion years ago, he says. Other researchers have found signs of life dating back at least that far, but those findings are even more controversial than Schopf's.

Also at University of Wisconsin-Madison.

Previously: Ancient Rocks Record First Evidence for Photosynthesis That Made Oxygen
3.7 Billion-Year-Old Fossil Found
Oldest Evidence of Life on Earth Found in 3.77-4.28 Billion Year Old Fossils
Earliest Known Evidence for Microbial Life on Land: 3.48 Billion Years Old


Original Submission

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  • (Score: 2) by requerdanos on Saturday October 20 2018, @06:09PM

    by requerdanos (5997) Subscriber Badge on Saturday October 20 2018, @06:09PM (#751437) Journal

    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 a couple of years ago.

    Don't worry, Earth, your neighbor Mars has the same problem [space.com].

  • (Score: 3, Interesting) by RandomFactor on Saturday October 20 2018, @06:22PM (2 children)

    by RandomFactor (3682) Subscriber Badge on Saturday October 20 2018, @06:22PM (#751441) Journal

    We keep pushing the earliest signs of life back. 4.28 billion years ago? Earth was formed 4.54 billion years ago

    If we are looking at the beginnings of life just a few hundred million years after the planet was formed, it seems that this should bode well for the likelihood of life existing elsewhere in the universe.

    --
    В «Правде» нет известий, в «Известиях» нет правды
    • (Score: 2) by bzipitidoo on Saturday October 20 2018, @08:27PM (1 child)

      by bzipitidoo (4388) Subscriber Badge on Saturday October 20 2018, @08:27PM (#751469) Journal

      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

        by takyon (881) <reversethis-{gro ... s} {ta} {noykat}> on Saturday October 20 2018, @09:32PM (#751481) Journal

        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]
  • (Score: 0) by Anonymous Coward on Saturday October 20 2018, @07:41PM (4 children)

    by Anonymous Coward on Saturday October 20 2018, @07:41PM (#751458)

    Y'all know life started 6000 years ago, why bother with this science stuff?

    • (Score: 3, Touché) by bzipitidoo on Saturday October 20 2018, @08:06PM (3 children)

      by bzipitidoo (4388) Subscriber Badge on Saturday October 20 2018, @08:06PM (#751465) Journal

      Yeah, no need for accuracy either. As I recall, I heard that 6000 years old stuff quite a few years ago. Meaning, by now, in the Year of Our Lord 2018, the correct figure ought to be a bit higher than 6000. Maybe 6018?

      • (Score: 0) by Anonymous Coward on Saturday October 20 2018, @08:29PM (2 children)

        by Anonymous Coward on Saturday October 20 2018, @08:29PM (#751470)

        close. 6022 more or less. the world was born on September 21, 4004 BC. [wikipedia.org] (gregorian calendar. October 23, 4004 BC julian calendar)

        • (Score: 0) by Anonymous Coward on Saturday October 20 2018, @09:15PM (1 child)

          by Anonymous Coward on Saturday October 20 2018, @09:15PM (#751477)

          Infidel! Allah started to create the world 300,000 years ago. Please report to your nearest Saudi embassy for execution and dismemberment.

          • (Score: 4, Touché) by MostCynical on Saturday October 20 2018, @09:41PM

            by MostCynical (2589) on Saturday October 20 2018, @09:41PM (#751484) Journal

            Please report to your nearest Saudi embassy for execution and dismemberment papers, which may escalate into a fight.

            FTFY

            --
            "I guess once you start doubting, there's no end to it." -Batou, Ghost in the Shell: Stand Alone Complex
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