UMD Geology Ph.D. Student Helps Discover Remains of a Recent Glacier Near Mars’ Equator

This discovery indicates that water ice might still exist at shallow depths at low latitudes on Mars, bringing researchers closer to understanding how the planet was and still may be habitable.

Researchers announced the discovery of the remains of a modern glacier near Mars’ equator on March 16, 2023, at the 54th Lunar and Planetary Science Conference. These remains, which the scientists described as a large surface deposit of light-colored sulfate salts, indicate that Mars’ recent history may have been more watery and thus more capable of sustaining life than previously thought. According to the team, which includes University of Maryland geology graduate student Sourabh Shubham, this discovery has significant implications for understanding Mars’ past and present habitability.

“What we’ve found is not ice, but a salt deposit with the detailed morphologic features of a glacier,” said the study’s lead researcher Pascal Lee, a planetary scientist with the SETI Institute and the Mars Institute. “What we think happened here is that salt formed on top of a glacier while preserving the shape of the ice below, down to details like crevasse fields and moraine bands.”

The team estimated that the remains of the Mars glacier are at least 4 miles long and up to 2.5 miles wide. The site is located approximately a mile high on Mars. Shubham, who conducted the remote sensing analyses to support the study’s findings, helped the scientists determine the composition of the salts and figure out how these salts (sulfates) might have accumulated in the first place.

“This region of Mars has a history of volcanic activity. And where some of the freshly erupted volcanic materials—like ash, pumice and hot lava blocks—came in contact with glacier ice, chemical reactions would have taken place at the boundary between the two, resulting in a hardened layer of sulfate salts,” Shubham said. “This is the most likely explanation for the hydrated and hydroxylated sulfates we observe in this light-toned deposit.”

Over time, as those volcanic materials eroded away, it revealed a crusty layer of sulfates mirroring the glacier ice underneath, including certain features unique to glaciers such as crevasses and moraine bands (strips of rock and soil debris transported by moving ice).

The team further observed that the glacier’s fine-scale surface features were also very sparsely cratered by impacts—indicating that the glacier is likely to be relatively young, geologically speaking. As a rule of thumb, older surfaces have been exposed to impacting celestial bodies like asteroids and comets for a much longer amount of time than younger surfaces, which explains why older surfaces tend to have more impact craters.

“Our team estimates that the original glacier is likely Amazonian in age, the latest geologic period which includes modern Mars,” Shubham explained.

For the team, this was an especially surprising discovery; scientists have known about glacial activity on Mars at many different locations and at higher latitudes, but the relatively young remnants of this glacier indicate that Mars experienced surface ice in recent times even at low latitudes near its equator, generally the planet’s warmest location.

It remains to be seen whether water ice is still preserved beneath the light-toned deposit or if it has disappeared entirely. Currently, water cannot exist in liquid form on the surface of Mars near the equator at this elevation, as Mars’ low atmospheric pressure and temperature would cause water to sublimate (evaporate from ice to gas directly, skipping the liquid phase) away. However, the team believes it possible that some water ice might still be present, protected at shallow depths under the sulfate salts.

“On Earth, we have ice islands on salt lakebeds, or salars, located in the Altiplano in South America. There, old glacier ice remained protected from melting, evaporation and sublimation underneath blankets of bright salts,” Lee said. “We hypothesize a similar situation to explain how sulfate salts on Mars might be able to offer protection to otherwise sublimation-vulnerable ice at low latitudes on the planet.”

Ultimately, if water ice is still preserved at shallow depths near Mars’ equator and similarly low latitudes of the planet, it could have significant implications for future research and human exploration.

“The desire to land humans at a location where they might be able to extract water ice from the ground has been pushing mission planners to consider higher latitude sites, but the latter environments are typically colder and more challenging for humans and robots,” Lee explained. “If there were equatorial locations where ice might be found at shallow depth, then we’d have the best of both environments: warmer conditions for human exploration and still access to ice.”

Lee cautioned that more research is needed: “We now have to determine if, and how much, water ice might actually be present in this relict glacier, and whether other light-toned deposits might also have, or have had, ice-rich substrates.”

Sourabh Shubham is expected to continue investigating this region on Mars with the team while he also advances research on instrument development with his Ph.D. advisor at UMD, Ricardo Arévalo, Jr.

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This article was adapted from text provided by the SETI Institute.

This work was supported by NASA and the Mars Institute. This story does not necessarily reflect the views of these organizations.

The study, “A relict glacier near Mars’ equator: evidence for recent glaciation and volcanism in Eastern Noctis Labrynthus,'' was presented at the 54th Lunar and Planetary Science Conference held March 13-17, 2023.