In 2017, paleontologists found 3.75- to 4.28-billion-year-old microscopic filaments and tubes, which appeared to have been made by iron-loving bacteria, in rocks from the Nuvvuagittuq Supracrustal Belt in Québec, Canada. However, not all scientists agreed that these structures — dating about 300 million years earlier than what is more commonly accepted as the first sign of ancient life — were of biological origin. Now, after extensive further analysis of the Nuvvuagittuq rocks, the paleontologists have discovered a much larger and more complex structure — a stem with parallel branches on one side that is nearly 1 cm long — as well as hundreds of distorted spheres, or ellipsoids, alongside the tubes and filaments. While some of these structures could conceivably have been created through chance chemical reactions, the tree-like stem with parallel branches was most likely biological in origin, as no structure created via chemistry alone has been found like it. The new findings suggest that a variety of microbial life may have existed on primordial Earth, potentially as little as 300 million years after the planet formed.
Transmitted light image of a bundles of pectinate-branching hematite filaments with undulations and tubes and co-occurring clusters of irregular ellipsoids from the Nuvvuagittuq Supracrustal Belt, Québec, Canada. Image credit: Dominic Papineau.
“Using many different lines of evidence, our study strongly suggests a number of different types of bacteria existed on Earth between 3.75 and 4.28 billion years ago,” said Dr. Dominic Papineau, a paleontologist at the China University of Geosciences, the London Centre for Nanotechnology, the Department of Earth Sciences, and the Centre for Planetary Sciences at University College London & Birkbeck College London.
“This means life could have begun as little as 300 million years after Earth formed. In geological terms, this is quick — about one spin of the Sun around the Milky Way Galaxy.”
“These findings have implications for the possibility of extraterrestrial life,” he added.
“If life is relatively quick to emerge, given the right conditions, this increases the chance that life exists on other planets.”
For the study, Dr. Papineau and colleagues examined rocks from the Nuvvuagittuq Supracrustal Belt that they collected in 2008.
Once a chunk of seafloor, the Nuvvuagittuq Supracrustal Belt contains some of the oldest sedimentary rocks known on Earth, thought to have been laid down near a system of hydrothermal vents.
The paleontologists sliced the rock into sections about as thick as paper (100 microns) in order to closely observe the tiny fossil-like structures, which are made of hematite and encased in quartz.
These slices of rock, cut with a diamond-encrusted saw, were more than twice as thick as earlier sections the researchers had cut, allowing the team to see larger hematite structures in them.
They compared the structures and compositions to more recent fossils as well as to iron-oxidizing bacteria located near hydrothermal vent systems today.
They found modern-day equivalents to the twisting filaments, parallel branching structures and distorted spheres, for instance close to the Loihi undersea volcano near Hawaii, as well as other vent systems in the Arctic and Indian oceans.
Hematite tubes from the NSB hydrothermal vent deposits found in 2017. Image credit: Matthew Dodd, University College London.
Using micro-CT and ion beam techniques, the scientists confirmed the hematite filaments were wavy and twisted, and contained organic carbon, which are characteristics shared with modern-day iron-eating microbes.
In their analysis, they concluded that the hematite structures could not have been created through the squeezing and heating of the rock (metamorphism) over billions of years, pointing out that the structures appeared to be better preserved in finer quartz (less affected by metamorphism) than in the coarser quartz (which has undergone more metamorphism).
The authors also looked at the levels of rare earth elements in the fossil-laden rock, finding that they had the same levels as other ancient rock specimens.
This confirmed that the seafloor deposits were as old as the surrounding volcanic rocks, and not younger imposter infiltrations as some have proposed.
“Our unprecedented findings contribute to the search for extraterrestrial life by demonstrating that multiple co-occurring biosignatures, including microfossils, dubiofossils, abiotic diagenetic microstructures, trace element compositions, and minerals associated with expected products from diagenetically oxidized biomass can yield a well-supported interpretation for early biological evolution,” the scientists said.
“This discovery implies that only a few hundred million years are needed for life to evolve to an organized level on a primordial habitable planet.”
“We therefore conclude that such microbial ecosystems could exist on other planetary surfaces where liquid water interacted with volcanic rocks, and that these oldest microfossils and dubiofossils from the Nuvvuagittuq Supracrustal Belt suggest that extraterrestrial life may be more widespread than previously thought.”
The team’s paper was published in the journal Science Advances.
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Dominic Papineau et al. 2022. Metabolically diverse primordial microbial communities in Earth’s oldest seafloor-hydrothermal jasper. Science Advances 8 (15); doi: 10.1126/sciadv.abm2296
Source link: https://www.sci.news/paleontology/nuvvuagittuq-fossils-10712.html
