Frost was detected 21.5 km above the surface of Mars, marking the first time scientists have observed frozen water so close to the planet’s equator. This discovery challenges previous assumptions that frost formation around the Martian equator was impossible due to the planet’s slender atmosphere and intense sunlight.
Perspective view of Olympus Mons from Mars Express, with frost (blue) in the cauldron-like depression (Image: European Space Agency)
“We believed that frost could not form around Mars’ equator because the combination of sunlight and a slender atmosphere kept temperatures relatively high both at the surface and at the top of the mountain – unlike what we see on Earth, where we can expect frosty peaks ” said lead author Adomas Valantinas, who made the discovery as a PhD student at the University of Bern in Switzerland and is now a postdoctoral researcher at Brown University in the US “Its existence here is exhilarating and indicates that unique processes occur within it that allow frost formation.”
Valantinas and his team spent five years analyzing data from the European Space Agency’s Trace Gas Orbiter (TGO) and Mars Express Orbiter, painstakingly analyzing more than 30,000 images of the region. Their research showed that during the Martian winter months, a fine layer of frost forms on the peaks of Olympus Mons and other volcanoes in the Tharsis region, as slender as a human hair and probably only one-hundredth of a millimeter stout. This frost, although slender, covers a wide area and contains an estimated 150,000 tons of water – the equivalent of about 60 Olympic swimming pools – which briefly moves between the surface and the atmosphere each day during the icy season before evaporating under the Martian sun.
The formation of frost is attributed to the unique microclimate created by air circulation around mountain peaks and calderas, which are collapsed craters created by massive volcanic eruptions millions of years ago. These conditions allow the air to nippy enough for frost to form, albeit briefly, on Martian mornings. Patches of frost appear for a few hours around sunrise before evaporating in sunlight, revealing the fascinating cycle of water activity on Mars.
“What we’re seeing could be a remnant of an historic climate cycle on newfangled Mars, where these volcanoes experienced precipitation and maybe even snow in the past,” Valantinas said. “The amount of frost corresponds to about 1,50,000 tons of water exchanged between the surface and the atmosphere each day during the icy season, equivalent to about 60 Olympic-size swimming pools.”
The presence of frost suggests that water vapor moves through the Martian atmosphere and condenses in specific areas, challenging the idea that Mars is completely devoid of vigorous hydrological processes.
“This discovery could be crucial for modeling the existence of water on Mars, which could assist in future human exploration missions,” Valentinas explained. The authors of the study hope that further research and computer simulations of frost formation and evaporation processes will shed lightweight on the dynamics of water on Mars and influence future exploration strategies.
