An article published in the journal “Science Advances” reports the discovery of microfossils of the oldest known methanogenic microorganisms, with an estimated age of 3.42 billion years. A team of researchers led by Professor Barbara Cavalazzi of the University of Bologna, Italy, discovered these microfossils in South Africa, in the area known as the Barberton Greenstone Belt. These microorganisms lived in a system of hydrothermal veins and show similarities with today’s archaea. Their study offers insights into early life forms on Earth and the possibilities for life forms to emerge in similar environments elsewhere in the universe.
The reconstruction of the early stages of the evolution of life forms on Earth is made difficult by the scarcity of fossils and the fact that they are microorganisms, with the problem of having to examine microscopic structures. In the Barberton Greenstone Belt, some of the oldest and best-preserved sedimentary rocks in the world can be found and this offers very interesting possibilities in the search for microfossils.
Archaea can fossilize but there are few examples of findings. It’s therefore no coincidence that microfossils of microorganisms that show similarities with today’s archaea have been found in the area of Barberton Greenstone Belt in an excellent state of conservation despite the estimated age of about 3.42 billion years.
One of the candidate places for the origin of the earliest life forms on Earth, and perhaps elsewhere, are the hydrothermal vents and they were present in today’s Barberton Greenstone Belt at the time when the discovered microorganisms lived. Many scientists studying the origin of life are interested in hydrothermal vents because they contain all the elements needed to achieve complex chemical reactions. The energy generated by a volcanic activity makes it possible to make the many simple molecules that are mixed by the hydrothermal activity react, including the minerals released into the water from that type of source. The one found in this study is the oldest ecosystem discovered so far, a clue that life indeed emerged in that type of environment.
Microfossils were submitted to a series of microscopic and spectroscopic examinations to ascertain their biological nature and examine their structures. Sometimes controversies arise because some non-biological processes can generate structures similar to primitive microorganisms. In this case, the researchers’ conclusion is that they are indeed fossils of life forms.
This study offers new insights into the life forms that existed on Earth 3.42 billion years ago. It’s also a useful study in the field of astrobiology, which studies the possibilities of extraterrestrial life forms. In the case of hydrothermal vents, there are not only hypotheses related to exoplanets that may be very distant but also studies connected to the vents identified in the underground oceans of Europa, one of Jupiter’s moons, and Enceladus, one of Saturn’s moons. Even on Mars, when this planet was young, there were such environments and in the subsoil, there could still be life forms based on particular metabolisms that might produce at least part of the methane identified on the red planet. In short, these are studies that could have significant developments in the coming years.