Water frost has been spotted atop Mars' gargantuan equatorial volcanoes for the first time — defying previous beliefs that the presence of water there was impossible.

Scientists spotted a hair-thin dusting of frost atop the peaks of the volcanoes in the Tharsis region of the Red Planet — the largest mountains in the solar system, which tower up to three times the height of Mount Everest. In colder months, the frost could consist of up to 150,000 tons of water, or the equivalent of 60 Olympic swimming pools. 

"We thought it was improbable for frost to form around Mars' equator, as the mix of sunshine and thin atmosphere keeps temperatures during the day relatively high at both the surface and mountaintop — unlike what we see on Earth, where you might expect to see frosty peaks," lead study author Adomas Valantinas, a postdoctoral fellow at Brown University, said in a statement. 

The scientists discovered that the frost condenses along the summits of the mountains each night, before evaporating under the heat of the morning sun. The finding could be crucial for modeling water's existence on Mars that could aid in future human exploration missions. The researchers published their findings June 10 in the journal Nature Geoscience.