Perseverance rover marks first anniversary on Mars
NASA’s Perseverance rover is one year into a two-year mission to explore the dry river delta and drill into rocks that may hold evidence of life. (Feb. 16)
- Scientists analyzed halite samples from 830 million years ago using optical techniques.
- Inside the samples, they found microorganisms such as bacteria, algae and fungi that may still be alive.
- NASA could use similar techniques when the Perseverance rover returns to Earth.
Scientists at West Virginia University may have found living microorganisms in a halite sample dating back 830 million years, giving researchers a look into past life and environments.
The study was published in scientific journal the Geological Society of America. Scientists looked at a sample from the 830-million-year-old Browne Formation of central Australia, drilled by the Geological Survey of Western Australia in 1997. They looked at 10 halite beds and used a razor blade to split the halite into 1 to 2 millimeter pieces.
The team analyzed neoproterozoic halite using non-invasive optical methods, allowing the halite to stay intact during the study and eliminate the risk of contamination by modern organisms.
They used transmitted light petrography to identify halite crystals and fluid inclusions, or water that was trapped as the halite crystals formed. They were also able to see what was inside the individual fluid inclusions, including microorganisms such as bacteria, algae or fungi. Now, scientists say some of these 830-million-year-old microorganisms could still be alive.
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At high magnification using both transmitted light and UV-visible light, the researchers saw what was inside individual fluid inclusions – microorganisms that were living in the water near the surface of the crystal millions of years ago.
They found prokaryotes, or bacteria or archaea, that looked clear, white, or pale orange, said Sara Schreder-Gomes, lead researcher on the study. They also found eukaryotic cells that are likely salt-loving algae or fungi that looked yellow, pale orange, pale brown or clear.
Some of the eukaryotic cells had a ‘halo’ coating of organic compounds around them, Schreder-Gomes said.
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According to the team, as halite grows from salty surface waters, fluid inclusions entrap the water, becoming microenvironments or habitats for trapped microorganisms. The bacteria and salt-loving algae or fungi found inside the halite were trapped when the crystals formed, making them 830 million years old, the researchers said.
But figuring out whether the microorganisms are still alive and how they’ve survived this long is the tricky part.
Microorganisms found in the halite shrink and greatly reduce biological activity when host waters become too salty, the researchers said. These algal cells may be revived during later flooding events, based on past studies. Bacteria has also survived in halite fluid inclusions as well, they said, making it likely that the microorganisms from the most recent sample are alive.
Taking things a step further, the researchers said it’s possible that ancient chemical sediments, both on and off earth, could host ancient microorganisms and organic compounds like those found in the halite samples.
Schreder-Gomes said their work could help researchers at NASA.
For example, the NASA Perseverance rover, which landed on Mars on Feb. 18, 2021, is collecting samples for a future return to Earth, she said.
The Browne Formation her team studied contains similar deposits of minerals such as halite and gypsum to those found on Mars. Therefore, microorganisms that may have existed in water on Mars in the ancient past may be trapped inside halite, she said.
To find out, researchers must use similar non-destructive, optical techniques to look at samples the rover brings back to Earth, she said.
Lidya Tarhan is an assistant professor in the Department of Earth and Planetary Sciences at Yale University and said it’s unusual to have such a “well-preserved window into microbial life from this time interval, and captured, essentially, straight from seawater in these droplets of water that are then incorporated into these in these rock salt crystals.”
Part of the reason it’s so hard to say if they are alive or not is because the microorganisms are so small, she said. While scientists can observe larger organisms to determine whether they are still alive, it’s difficult to do with smaller ones.
Based on the researchers’ work and the properties they described of the organic cells, the majority of them are not alive and some of them are even decaying, Tarhan told USA TODAY.
But some of the organisms could still be kicking, she said, calling it exciting.
“This is a really fantastic snapshot of life 830 million years ago,” she said. “We have this really extraordinary window into the sorts of organisms that were either being transported to salty shoreline deposits and captured by these fluid inclusions, or (organisms) that were living in those super salty, hyper salty waters.”
Saleen Martin is a reporter on USA TODAY’s NOW team. She is from Norfolk, Virginia and loves all things horror, witches, Christmas and food.
Saleen Martin, email@example.com, Twitter: @Saleen_Martin