(CNN) Remains of a glacier have been found near the Martian equator, indicating that a form of water still exists in an area of the Red Planet where humans might one day land.
The glacier is no longer there, but scientists have spotted telltale remnants among other mineral deposits near Mars’ equatorial region. The sediments there usually contain light-colored sulfate salts.
When the scientists took a closer look, they recognized features of the glacier, including ridges called moraines—debris deposited or pushed up by a moving glacier. The research team also discovered rift fields, or deep wedge-shaped openings that form within glaciers.
The results were shared Wednesday at the 54th Lunar and Planetary Science Conference in The Woodlands, Texas.
“What we found is not ice, but rather a salt deposit with the detailed morphological features of a glacier,” lead study author Dr. Pascal Lee, a planetary scientist with the SETI Institute and the Mars Institute, said in a statement.
“What we think happened here is that the salt formed on top of a glacier while maintaining the shape of the ice below, down to details like fault fields and moraine bands.”
Researchers believe the glacier was 3.7 miles (6 kilometers) long and 2.5 miles (about 4 kilometers) wide, with a height of between 0.8 to 1.1 miles (1.3 to 1.7 kilometers).
Volcanic activity creates a protective layer
Scientists have an idea of how the glacier footprint might have come about, based on evidence of volcanic material in the area. When mixtures of volcanic ash, lava, and volcanic glass called pumice react with water, a hard, crusty salt bed can form.
“This region of Mars has a history of volcanic activity. Where some volcanic material came into contact with icy ice, chemical reactions were occurring at the boundary between the two to form a solid layer of sulfate salts,” the study said. Sarab Shubham, PhD student in geology at the University of Maryland, College Park, in a statement.
“This is the most likely explanation for the hydrated and hydroxylated sulfate we are observing in this light-colored sediment.”
A geologically small ice surface near the equator
The volcanic material likely eroded over time, revealing the salty layer that picked up the imprint and distinct characteristics of glacial ice, said study co-author John Schott, a geologist with the Mars Institute and Ice Guides in the Arctic and Antarctica.
Mars has a thin atmosphere that allows space rocks to collide regularly with the planet’s surface. But the glacier’s subtle, detailed features remain largely undisturbed in the salt deposits, leading researchers to believe it is relatively “young”.
The study authors said they believe the glacier was present during Mars’ Amazonian geological period, which began 2.9 billion years ago and is still ongoing.
“We’ve known of glacial activity on Mars in many locations, including near the equator in the distant past. We’ve known of recent glacial activity on Mars, but so far, only at higher latitudes,” Lee said. “One relatively young glacier at this location tells us that Mars has encountered surface ice recently, even near the equator, which is novel.”
The researchers don’t know if there is any ice left under the sediments.
“At present, water ice is unstable on Mars itself near the equator at these altitudes,” Lee said. “Therefore, it is not surprising that we did not detect any water ice at the surface. It is possible that all of the glacier’s water ice has melted away now. But there is also a possibility that some of it remains protected at shallow depths under the sulfate salts.”
Possible shallow ice pockets
During the study, the team also looked at ancient glacial islands called Salars in the salt flats of the Altiplano in Bolivia in South America. Blankets of salts protected ancient glacial ice from melting or evaporating, leading researchers to believe a similar scenario may have occurred on Mars.
Next, the researchers want to determine if there is any ice left from the glacier, and if so, how much is there at the shallow depths beneath the salt deposits. If these salt deposits protect the ice, other pockets of ice are likely in the vicinity.
Orbits around the planet have shown deposits of ice at Mars’ frigid poles, but if water in any form is present at warmer lower equatorial latitudes, it could have implications for our understanding of the Red Planet’s history and habitability – and future exploration by humans.
“The desire to land humans in a place where they can extract water ice from the Earth is leading mission planners to consider higher latitude locations,” Li said. “But the latter environments are usually cooler and more challenging for humans and robots. If there are tropical locations where ice can be found at shallower depths, we’ll have the better of both environments: warmer conditions for human exploration while still having access to ice.”
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