Millions of years old organisms found trapped in ancient rock
An astonishing discovery has just been made about a potential new source for understanding life on ancient Earth.
A team of geologists discovered tiny remnants of prokaryotic life and algae - trapped inside halite crystals dating back 830 million years.
Halite is known as sodium chloride, also known as rock salt, and the discovery indicates that this natural mineral could be a previously untapped resource for studying ancient saltwater environments.
Moreover, the organisms trapped in it might still be alive.
Ancient microfossils were found compressed in rock formations, such as shale, dating back billions of years. Salt is not able to preserve organic matter in the same way.
Alternatively, when crystals form in a saltwater environment, small amounts of liquid can be trapped inside. These are called fluid impurities, and are the remains of the mother water from which the halite crystallized.
This makes them of scientific value, because they can contain information about the temperature of the water, the chemistry of the water, and even the temperature of the atmosphere at the time the mineral was formed.
Scientists also found microorganisms that live in modern environments where halite is formed. These environments are highly saline, however, microorganisms such as bacteria, fungi and algae were found thriving in them.
In addition, microorganisms have been documented in fluid inclusions in gypsum and halite, mostly modern, with a handful going back to antiquity. However, the method of identifying these ancient creatures left some doubt as to whether they were the same age as halite.
“Therefore, there has been a question among microbiologists," a team led by geologist Sarah Schrader Gomez of West Virginia University wrote. What are the oldest chemical sedimentary rocks containing prokaryotic and eukaryotic microorganisms
? from the sedimentary environment”
Central Australia is now known as a desert, but it was once an ancient salt sea. The Brown Formation is a well-characterized and dated stratigraphic unit from central Australia, dating back to the Cenozoic. They include extensive halite, indicative of a paleo marine environment.
Using a core sample of Brown Formation extracted by the Western Australian Geological Survey in 1997, Schrader-Gómez and colleagues were able to conduct investigations of unaltered nepproterozoic halite using non-invasive optical methods. This will leave the halite intact. Which means, importantly, that anything inside had to be trapped by the time the crystals formed.
They used ultraviolet lithography and transmitted light, first at low magnification to identify halite crystals, and then magnification up to 2,000 times to study liquid impurities in them.
Inside, they found organic solids and liquids compatible with prokaryotic and eukaryotic cells, based on their size, shape and ultraviolet fluorescence.
The radiance range was also interesting. Some samples showed colors consistent with organic decomposition, while others showed the same fluorescence of modern organisms, suggesting, the researchers said, of unchanged organic materials.
The researchers pointed out that it is possible that some organisms are still alive. And the fluid contents can serve as micro-habitats where small colonies thrive. Live prokaryotes have been extracted from halite dating back 250 million years.
The researchers wrote: "The potential survival of microorganisms on geologic time scales that is not fully understood. It was suggested that radiation would destroy organic matter over long periods of time, however it was found that buried halite, which is 250 million years old, was exposed to only trace amounts of radiation. In addition, microorganisms may live in liquids.
This certainly has implications for Mars, the researchers said, where deposits with similar compositions to Brown's can be found. Their research shows how these organisms can be identified without destroying or disrupting specimens, which could give us a new set of tools to learn about them — and to better understand Earth's history, too.
The team wrote: "Visual examination should be considered an essential step in any study of biosignatures in ancient rocks. It allows knowledge of the geological context of microorganisms prior to further chemical or biological analyses, and provides a target for such analyses. Ancient chemical deposits, both terrestrial and of extraterrestrial origin, should be considered as potential hosts for ancient microorganisms and organic compounds.”
The research was published in the Journal of Geology.
Source: Science Alert
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