To reach this conclusion, exobiologist Dominic Papineau and his colleagues analyzed a rock from the Nuvvuagittuq belt, located on the coast of Hudson Bay in Quebec. This rock formation is known to contain the oldest sediments in the earth’s crust.
and 4.28billions of years ago”,”text”:”Using many different lines of evidence, our study strongly suggests that a number of different types of bacteria existed on Earth between 3.75 and 4.28 billion years ago. “}}”>Using many different lines of evidence, our study strongly suggests that a number of different types of bacteria existed on Earth between 3.75 and 4.28 billion years ago.says Professor Papineau.
As early as 2017, a team in which Dominic Papineau participated had published in the journal Nature a study describing structures present in rock from the same belt that most likely belonged to fossilized microorganisms dating between 3.8 and 4.3 billion years ago.
This assessment pushed back the oldest known traces of life on Earth by 100 million or even 600 million years. It was quickly challenged by other scientists who were not convinced that the structures observed were indeed of biological origin. According to them, the tiny hematite filaments, knobs and tubes observed in the rock could not be than organic, that is to say created by chemical reactions.
In the current work, Professor Papineau and his team analyzed a rock from the same belt in more detail.
” We cut the rock into sections about as thick as paper [100 microns] to get a close look at the tiny fossil structures, which are made of hematite, a form of iron oxide or rust, and encased in quartz. »
These slices of rock were more than twice as thick as the previous sections the researchers had cut [en 2017]adds Professor Papineau.
The researchers discovered a much larger and more complex hematite structure there.
” This structure forms a stem with parallel branches on one side that is almost a centimeter long. There are also hundreds of distorted spheres […] associated with tubes and filaments that often end in a corkscrew. »
Professor Papineau acknowledges that some of these structures may have appeared as a result of chemical reactions, but he believes that the tree-like stem with parallel branches is most likely of biological origin. According to him, no structure created solely by non-biological chemistry has been found like this, either in the laboratory or in nature.
In addition, the UCL team compared the observed structures to more recent fossils, but also to iron-oxidizing bacteria located near present-day hydrothermal vent systems.
” We have found modern equivalents of twisted filaments, parallel branching structures and distorted spheres, for example near the submarine volcano Loihi, off Hawaii. »
This work also provides evidence that bacteria draw their energy from different sources. Indeed, researchers have found mineralized chemical by-products in the rock that correspond to ancient microbes living on iron, sulfur and possibly also carbon dioxide and light through a form of photosynthesis not involving photosynthesis. ‘oxygen.
Published in the journal Science Advances (New window) (in English), the results of this study lead scientists to believe that a variety of microbial life already existed on early Earth.
” This means that life could have started as little as 300 million years after the formation of the Earth. In geological and astronomical terms, it’s fast! It’s about one revolution of the Sun around the galaxy. »
The scientist draws a parallel between his conclusions and the search for extraterrestrial life, for example on Mars and on the moons of Saturn and Jupiter (like Enceladus or Europa).
” Our data open up several avenues of investigation in terms of the evolution of metabolisms. At the biological level, we really push back the complexity of micro-organisms, which tells us about the origin of life. »
These findings have implications for the possibility of extraterrestrial life. If life is relatively quick to emerge, given the right conditions, it increases the likelihood that life exists on other planets.continues Professor Papineau.
This gives us a recipe idea of what to look for, how to look for it, and how to identify it.summarizes the researcher.