830 million year old microorganisms trapped in a mineral

Three geologists from West Virginia University (West Virginia University)Sara Schreder-Gomes, Kathleen Benison and Jeremiah Bernau, published an article in the review Geology May 6th. They discovered that inclusions of primary fluids in the halite of the Browne formation contain solid and liquids organic. Halite comes from the evaporation of salt lakes or seas which will create rocks highly concentrated in salt, called evaporitic rocks. The sample studied originates from central Australia and was formed 830 million years ago.

The organic traces found in this halite were determined by the method of light transmitted which made it possible to describe the size, shape and color of the materials organics, and through the method of ultraviolet visible petrography (UV-vis) which shows a fluorescent response for any microorganism and organic compound present. These techniques revealed that the halite sample contained cells of prokaryotes, eukaryotes and organic compounds. It has also been observed that the inclusions of fluids in which these are trapped microorganisms serve as their microhabitats and have allowed their exceptional conservation.

Are these microorganisms alive?

To survive in very salty environments, some organisms like algae shrink and reduce their biological activity, then wait for better conditions to wake up.

However, it is not yet known whether organisms can hibernate as long. The oldest halite in which prokaryotes have been extracted alive dates from around 250 million years ago, so it is possible that these microorganisms found in Australia could also be.

Until recently, it was suggested that the solar radiation destroyed organic matter over long periods of time. But the discovery of these microorganisms in halite from the 830 Ma Browne Formation is strong evidence that organic matter can be preserved in deposit crystals over a long geological time.

A way to find life on Mars?

Browne Formation halite is similar in structure and characteristics with Martian rocks. Indeed, Mars once knew spaces of salt water in which halite could have been created by evaporation. The results of this study therefore suggest the possibility of a similar preservation of microfossils in the sedimentary rocks of Mars, and may therefore be a new means of investigation to find out whether Mars once harbored life.

Old sedimentary rocks, terrestrial and extraterrestrial, therefore still have much to offer in terms of information about the past and it is therefore essential that geologists consider them as objects that can be composed of life.