Geologists have identified tiny lifeforms that have been trapped inside of crystals for 830 million years. And they are likely still alive. The prokaryotic and algal life is contained in tiny amounts of fluid within the samples of halite, aka rock salt. Geologist Sara Schreder-Gomes of West Virginia University and colleagues suggest that their approach to analyzing the crystals could also be applied offworld, such as in the salt deposits on Mars. From Science Alert:
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[…]
It's even possible that some of the organisms are still alive, the researchers noted. The fluid inclusions could serve as microhabitats where tiny colonies thrive. And living prokaryotes have been extracted from halite dating back 250 million years; why not 830 million?
"Possible survival of microorganisms over geologic time scales is not fully understood," the researchers wrote.