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Potentially alive 830-million-year-old organisms found trapped in ancient rock

Baku, May 18, AZERTAC

An incredible discovery has just revealed a potential new source for understanding life on ancient Earth.

A team of geologists has just discovered tiny remnants of prokaryotic and algal life – trapped inside crystals of halite dating back to 830 million years ago.

Halite is sodium chloride, also known as rock salt, and the discovery suggests that this natural mineral could be a previously untapped resource for studying ancient saltwater environments.

Moreover, the organisms trapped therein may still be alive.

The extraordinary study also has implications for the search for ancient life, not just on Earth, but in extraterrestrial environments, such as Mars, where large salt deposits have been identified as evidence of ancient, large-scale liquid water reservoirs.

The organisms don't look like you might be expecting.

Previous ancient microfossils have been found pressed into rock formations, such as shale, dating back billions of years. Salt is not able to preserve organic material in the same way.

Instead, when the crystals are forming in a saltwater environment, small amounts of fluid can be trapped inside. These are called fluid inclusions, and they're remnants of the parent waters from which the halite crystallized.

This makes them scientifically valuable, since they can contain information about the water temperature, water chemistry and even atmospheric temperature at the time the mineral formed.

Scientists have also found microorganisms living in recent and modern environments where halite forms. These environments are extremely salty; nevertheless, microorganisms such as bacteria, fungi and algae have all been found thriving in them.

Moreover, microorganisms have been documented in fluid inclusions in gypsum and halite, mostly modern or recent, with a handful dating back to ancient times. However, the method of identifying these ancient organisms has left some doubt as to whether they are the same age as the halite.

Using a core sample from the Browne Formation extracted by the Geological Survey of Western Australia in 1997, Schreder-Gomes and her colleagues were able to conduct investigations of unaltered Neoproterozoic halite using nothing but non-invasive optical methods.

This left the halite intact; which, importantly, means that anything inside had to have been trapped at the time the crystals formed.

They used transmitted-light and ultraviolet petrography, first at low magnification to identify halite crystals, then at up to 2,000x magnification to study the fluid inclusions therein.

Inside, they found organic solids and liquids, consistent with prokaryotic and eukaryotic cells, based on their size, shape and ultraviolet fluorescence.

The research has been published in scientific journal - Geology.

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