It is an extraordinary, unusual possibility. Microorganisms 830 million years old could still be alive. Where? In the salt crystals in which they were trapped. They were found in Central Australia. Is it possible? The question is raised in the journal ‘Geology’.
In the depths
West Virginia University leads the study. They saw the organisms inside small pockets of liquid, thinner than a hair. They are in salt crystals (halite) from an ancient sedimentary rock formation. They are single-celled creatures. They lived almost a billion years ago in shallow, salty waters. For now they do not know if any of these creatures are still alive.
Most techniques for studying these crystals involve their destruction. They are based on extracting the fluids with a syringe or directly crushing them. It is difficult to establish the age of the microorganisms within the fluid.
The fluid pockets form at the same time as the glass itself. It means that whatever is trapped inside will have the same age. They thought of a new technique that does not destroy the crystals. First they took samples of halite at a depth of between 1,481 and 1,520 meters below the present surface. They cut them into one-millimeter-thick slices. They then examined the halite under a microscope with both visible and ultraviolet light. This was done without breaking the liquid pockets and magnifying them up to 2,000 times.
Similar to Mars
Inside, both eukaryotes (algae and fungi with cell nuclei) and prokaryotes (bacteria and archaea without nuclei). They are able to remain inactive for a long time. They alter their metabolism to stay alive when the water around them dries up. In 2000, a 250-million-year-old bacterium was claimed to have been successfully revived.
The technique would be used to search for ancient extraterrestrial life. The rocks studied in Australia were formed in an environment similar to that of ancient Mars. The Perseverance rover is storing Martian rocks that will be brought back to Earth in a few years. The 830-million-year-old microorganisms may have Martian cousins.
