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Underground salts, melting ice may explain Martian landslides

New research suggests near-surface cryosalt activity is responsible for the landslide-like flow patterns regularly photographed on warming Martian slopes. Photo by NASA/JPL/University of Arizona
New research suggests near-surface cryosalt activity is responsible for the landslide-like flow patterns regularly photographed on warming Martian slopes. Photo by NASA/JPL/University of Arizona

Feb. 3 (UPI) -- During the Red Planet's warm season, flow features proliferate across Martian slopes.

For years, NASA satellites have documented these seasonal landslides, but scientists have struggled to explain the phenomenon, known as recurring slope lineae.

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Previously, scientists have hypothesized that both liquid debris flows and dry granular flows could cause recurring slope lineae, but neither can entirely account for the seasonal pattern.

In a new paper, published Wednesday in the journal Science Advances, researchers suggest ice melting just beneath the Martian regolith is responsible for the flow patterns that spread across the Red Planet's warming slopes.

More specifically, researchers contend the seasonal landslides are triggered by interactions between melting ice and underground salts.

"I am excited about the prospect of microscale liquid water on Mars in near-surface environments where ice and salts are present," study author Janice Bishop said in a news release.

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"This could revolutionize our perspective on habitability just below the surface on Mars today," said Bishop, a research scientist with both the SETI Institute and NASA's Astrobiology Institute.

For the new study, researchers used a combination of field observations and lab experiments to build a model of near-surface cryosalt activity on Mars' warming slopes.

To better understand how cryosalt activity might influence regolith behavior on Mars, the researchers studied Martian-like environs on Earth -- places like Israel's Dead Sea and Salar de Pajonales in the Atacama Desert, where salt and water interact just beneath the surface.

"During my fieldwork at Salar de Pajonales, a dry salt bed in Northern Chile, I have observed numerous examples of the action of salts on the local geology," said study co-author Nancy Hinman.

"It's gratifying to find that it could play a role in shaping Mars as well," said Hinman, a SETI scientist and professor of geosciences at the University of Montana.

In the lab, scientists created analogs of the Martian regolith, the layer of dust and broken rocks that covers the Red Planet's surface.

When researchers froze and thawed the regolith layers, which were rich in chlorine salts and sulfates, they found a slushy ice solution formed at minus 50 degrees Celsius. Between minus 40 to minus 20 degree Celsius, the ice in the slush solution melted.

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"Probing the low-temperature behavior of Mars analog permafrost in the lab with infrared spectroscopy revealed that thin layers of liquid-like water were forming along grain surfaces as the salty soils thawed under subzero, Mars-like temperatures," said co-author Merve Yesilbas, a postdoctoral research fellow at SETI.

When researchers used their field observations and the results from the lab experiments to model sulfate-chloride interactions, they found near-surface cryosalt activity allows water molecules to flow easily through and across different salt molecules.

"I was thrilled to observe such rapid reactions of water with sulfate and chlorine salts in our lab experiments and the resulting collapse and upheave of Mars analog soil on a small scale, replicating geologic collapse and upheave features in karst systems, salt reservoirs, and edifice collapse on a large scale," said Bishop.

Imaging surveys have previously turned up evidence of subsurface ice on Mars, as well as elevated concentrations of sulfates and chlorides near recurring slope lineae.

The latest research suggests warming temperatures may trigger the formation of slush-like brines on Martian slopes, leading to the appearance and growth of landslide-like flow patterns.

Though Mars is devoid of obvious signs of life and hosts much less water than it did billions of years ago, the cryosalt activity model proposed by Bishop and company serves as a reminder that the Red Planet remains a highly dynamic environment.

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