Researchers at West Virginia University have been able to identify tiny remnants of prokaryotic and eukaryotic life trapped in 830 million year old halite crystals.
Microbial life trapped hundreds of millions of years ago
Described in the review Geologythis important discovery involved the use of petrography by transmitted and ultraviolet light to examine crystals ofhalite (or rock salt) from the depths of the formation Neoproterozoic from Brownein Australia. Although this area is now a desert, millions of years ago it was home to an ancient sea teeming with marine microbial life.
« When halite crystals grow in saline surface waters, they trap the parent water in primary fluid inclusions “, Explain Sara Schreder-Gomes, co-author of the study. ” They can also capture any solids in the water near or in contact with the face of the crystal. »
Some of these solids have been shown to exhibit properties (size, shape and fluorescent response to UV and visible light) corresponding to those of cells prokaryotes et eukaryotesas well as various organic compounds.
« Several of the crystals used in this study show an exceptionally high concentration of microorganisms and organic compounds at the primary fluid inclusions [jusqu’à 40 % d’entre elles en contiennent] “, detail the authors of the study. ” These allow exceptional preservation of organic matter over long periods of geological time. »
Potentially living organisms
According to the team, these organisms were trapped at the exact time the crystals formed, around 830 million years ago, and some of them may still be alive, surviving within these ” micro-habitats by feeding on organic compounds or dead cells, which provide the minute amounts of energy needed for a very slow metabolism.
If this hypothesis may seem absurd, in 2009, researchers from theuniversity of pennsylvania found that bacterial spores trapped in a 250-million-year-old fluid inclusion of halite survived, and many terrestrial organisms are known to thrive in particularly inhospitable environments.
Confirmation that the microorganisms present in the halite have indeed survived would have particularly important implications for the search for present and past life on Mars. The researchers specifying that many Martian sedimentary formations are similar to that of Browne and would therefore be prime targets.
