An international team of researchers led by scientists from the University of Bologna in Italy discovered the fossilized remains of microorganisms that fed on methane. These nuclear-free microorganisms (archaea) inhabited hydrothermal systems under the seabed more than 3.4 billion years ago.
The microfossils found by scientists are the oldest evidence of the existence of this life form. This find also expands the understanding of the conditions suitable for the emergence of life not only on Earth, but also on other planets: for example, on Mars.
Details of the new study have been published in the prestigious scientific journal Science Advances.
The specimens described were found in two thin layers of rock collected from the Mahondjwa Mountains in South Africa. The oldest well-preserved sedimentary rocks of our planet are found in this region.
Microscopic image of a filamentous fossil.
Photo by B. Cavalazzi / Università di Bologna.
The outer shell of the fossils found is rich in carbon and may be the remains of a cell wall (membrane). At the same time, inside the filamentous fossil, according to scientists, there is a condensed intracellular substance (cytoplasm).
“We found exceptionally well-preserved fossilized microorganisms. They appear to have inhabited the walls of voids created by warm water from hydrothermal systems located a few meters below the seafloor. unicellular ecosystems. And this is the oldest example found to date, "said lead author Professor Barbara Cavalazzi of the University of Bologna.
The interaction of colder seawater with warmer hydrothermal currents could create a rich chemical broth that could lead to a wide variety of microbial habitats.
Chemical analysis of filamentous fossils has shown that they contain most of the elements necessary for life. The concentration of nickel in these organic compounds became further evidence that a primitive metabolism took place in them.
They also correspond to the nickel levels found in modern archaea.
“Although we know that fossil remains of archaea exist, we had very few examples of such fossils. Our find for the first time may extend the fossil record of the Archaea to the time when life on Earth was just beginning,” added Professor Cavalazzi.
The authors of the work note that their study may also have implications for astrobiology. If such environments are found on planets like Mars, it could indicate the possible presence of life in them.