“Impossible” discovery of frost near the equator

Planetary scientists have long thought that Mars' equatorial regions were too sunny and its atmosphere too thin to accommodate frost or ice, but new images suggest otherwise.

A new article published in Natural geosciences revealed that the European Space Agency's ExoMars and Mars Express missions have spotted frozen water for the first time near Mars' equator, at its Tharsis Volcanoes, the tallest volcanoes in the solar system.

The region is home to the colossal Olympus Mons, three times taller than Mount Everest, and the Tharsis Montes shield volcanoes.

Exciting discovery

“We thought it was impossible for frost to form around Mars' equator, because the mix of sunlight and thin atmosphere keeps temperatures relatively high on the surface and on mountain tops,” said Dr. lead author Adomas Valantinas, who made the discovery while he was a doctoral student. student at the University of Bern, Switzerland, and is now a postdoctoral researcher at Brown University in Providence, Rhode Island.

“Its existence here is exciting and suggests that there are exceptional processes at play that allow the gel to form,” he said.

Unique microclimate

Mars is not like Earth, where frost peaks are common. Mars has low atmospheric pressure, which means that mountain peaks are about the same temperature as the plains. What scientists think is that moist air rises up mountain slopes and condenses as frost in the colder calderas of Tharsis volcanoes. The air circulates in such a way that it creates a microclimate never seen before.

The amount of frost found on Mars is equivalent to approximately 60 Olympic swimming pools. It was detected in very thin patches, but covers a large area. It only exists for a few hours at sunrise, before evaporating into the sun.

Late discovery?

The gel was discovered by ExoMars TGO and Mars Express, which have been conducting orbital research since 2018 and 2003, respectively. So why did it take so long to find this microclimate on Mars? “We need an orbit that allows us to observe a location early in the morning,” Valantinas said. Of the seven orbiters around Mars, all except ExoMars TGO and Mars Express are synchronized with the sun and therefore can only study Mars in the afternoon.

But there is another reason. “Frost deposits are linked to colder Martian seasons, which makes the window for spotting them even narrower,” Valantinas said. “You have to know where and when to look for short-lived frosts. We were looking for it near the equator for further research, but we didn't expect to see it on the tops of volcanoes on Mars.

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