- Shelly Carpenter/University of Washington
- In pockets of briny water 20 feet under the Arctic tundra, scientists have found thriving microbial communities.
- Some of these liquid pockets, called cryopegs, have remained untouched for 50,000 years.
- By studying the microbes that survive in these extreme environments, researchers can glean insight into what types of life to look for on planets like Mars or on Saturn’s moon Titan.
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Almost one-quarter of the Earth’s northern hemisphere remains frozen year-round.
This permanently chilled ground, aptly named permafrost, consists of soil, rocks and sand held together by ice. Sometimes, permafrost traps pockets of bacteria and viruses hundreds of thousands of years old.
These unchanging conditions and sub-zero temperatures make patches of permafrost suitable analogs for the icy conditions on other planets and their moons. So scientists are studying the microbes that survive and thrive there to glean insight into the kind of extraterrestrial life we might discover elsewhere in the solar system.
Recently, researchers from the University of Washington took a new approach to this effort, probing subsurface pockets where sediment mixes with salty water. These pockets under the Arctic tundra are called cryopegs, and some have remained untouched for 50,000 years.
As it turns out, some are also home to thriving groups of microscopic bacteria.
“We study really old seawater trapped inside of permafrost for up to 50,000 years, to see how those bacterial communities have evolved over time,” Zachary Cooper, an oceanographer who recently presented some of this research, said in a press release.
The team’s hope is that the tiny lifeforms they found could offer clues about what types of creatures we should hunt for on Mars or other planets.
Isolated for 50,000 years
In cryopegs, the water is so salty that the liquid remains unfrozen even at below-freezing temperatures.
To reach one of these underground pockets, Cooper and his colleagues drilled more than 20 feet into the permafrost near Utqiaġvik, Alaska.
They presented a DNA analysis of the bacteria that they discovered there at an astrobiology conference last month. To the researchers’ surprise, their analysis revealed that the isolated bacteria are thriving.
That shouldn’t be the case.
“The extreme conditions here are not just the below-zero temperatures, but also the very high salt concentrations,” Jody Deming, another study author, said in the press release. “140 parts per thousand – 14% – is a lot of salt. In canned goods, that would stop microbes from doing anything.”
- Zac Cooper/University of Washington
The primary microbe they found in the salty water was marinobacter, a common type of marine bacteria.
“Even though it has been in the dark, buried in frozen permafrost for a very long time, it originally came from the marine environment,” Deming said.
This shows that marinobacter are able to survive even when transplanted into a hyper-salty sediment pocket below the icy tundra.
“We were quite startled at how dense the bacterial communities are,” Cooper said. “We’re just discovering that there’s a very robust microbial community, co-evolving with viruses, in these ancient buried brines.”
Drilling into a subterranean tunnel
Researchers aren’t sure how cryopegs form under layers of ice. They could be former coastal lagoons that got trapped during the last ice age as the ocean receded.
To access this particular cryopeg, located about 20 to 25 feet below the surface, the researchers had to climb down a 12-foot ladder into the icy tundra, then crawl through a tunnel bored within the permafrost. The tunnel was only wide enough for a single person and not high enough to stand in.
Researchers then drilled into the tunnel floor to reach the cryopeg’s saline liquid.
Once they were finally able to analyze the samples they removed, the water turned out to be replete with tiny lifeforms.
Studying extreme environments could help scientists better understand Mars and Titan
These pockets of ancient saltwater could be very similar to the environments under the oceans and ice of other planets, the researchers wrote.
Mars may have once harbored a liquid ocean, and other moons in our solar system also have liquid water. Other ocean worlds include Saturn’s icy moons Titan and Enceladus, and Jupiter’s moons Europa and Ganymede.
Studying how Earthly bacteria thrives in semi-frozen liquid environments could inform future space-exploration missions about what kind of life to look for and how to detect it. The researchers behind the recent work think that the types of adaptations that allowed marinobacter to survive in hyper-salty, sub-zero water could also arise in bacteria on other planets.
Titan, specifically, is a prime candidate in the ongoing search for signs of extraterrestrial life. It’s Saturn’s largest moon and the second-largest moon in the solar system. Scientists refer to Titan as a “proto-Earth” because of its size, composition, and the bodies of liquid water on its surface. A colossal ocean of liquid water also likely exists below Titan’s roughly 60-mile-thick crust of ice.
Recently, NASA announced that its next $1 billion mission to space will send a nuclear-powered helicopter to explore Titan. The drone-like rotorcraft, nicknamed “Dragonfly,” is set to launch in 2026. Once it arrives at the distant moon, it will scan Titan’s surface seeking signs of past – or present – microbial alien life.