Martian volcanoes may have transported ice to the planet’s equator

The warmest areas of Mars host a curious thick ice layer beneath the surface, and scientists believe they’ve uncovered how it came to be. This ice might have been moved from inside the planet due to extraordinary volcanic eruptions billions of years ago, and it could prove vital for future manned missions.

While Mars is known to have ice, much of it has traditionally been understood to reside in the polar ice caps. However, radar data from orbiters has indicated significant ice exists in equatorial regions as well. “There’s this frozen layer at the equator—it’s unusual because it’s the planet’s hottest area,” remarks Saira Hamid from Arizona State University. Midday equatorial temperatures can reach around 20°C (68°F).

Hamid and her team conducted simulations of volcanic activity on Mars and concluded that, over millions of years, powerful eruptions could have propelled water from the interior into the atmosphere—when the planet had a denser atmospheric composition. This water would subsequently freeze and fall back to create the current ice layers. “It’s truly a tale of fire and ice,” Hamid notes.

These volcanic activities might have generated plumes of volcanic ash, water, and sulfur that could have soared to incredible heights—up to 65 kilometers above the surface or possibly even into space, depending on the atmospheric conditions during the eruptions.

After the materials settled, the water would transform into compacted dirty ice, protected by a layer of volcanic ash that would prevent sublimation into space, thereby preserving it well into the present day.

“The whole notion of such an ice-rich deposit has puzzled many scientists,” states Tom Watters from the Smithsonian Institution in Washington, D.C. A particularly intriguing feature is the Medusa Fossae Formation, a massive volcanic structure near Mars’ equator. “If you melted all the water we estimate in the Medusa Fossae formation, it would fill the Great Lakes. That’s a substantial amount of water,” he explains.

Another theory researchers considered for the abundance of ice involved changes in Mars’ obliquity—the tilt relative to the sun—possibly shifting the equator towards the poles at different points in its history. However, Hamid argues that with the volcanic eruptions, there’s no need to move ice from other regions of the planet or to rely on shifts in obliquity as an explanation; “It’s simply a straightforward answer.”

The equatorial area also serves as an ideal landing site for Mars missions due to the thicker atmosphere, which aids in slowing down landers during descent. Access to water in this region could be immensely beneficial for future human expeditions. While initial missions may not rely on it, subsequent landings could leverage the ice as a resource.

“For those early journeys, it’s critical to bring ample water in case our radar observations prove incorrect,” advises Watters. “I wouldn’t attempt to land without sufficient water, thinking I’d just dig and find some. It’s wise to bring both a shovel and enough water.”