Early morning frost detected on colossal Martian volcanoes

Early morning frost has been spotted on some of the largest mountains in the solar system - the colossal Martian volcanoes that rise up to three times the height of Mount Everest near the planet's equator.

- Ian Sample

In colder months the fine dusting of ice, thinner than a human hair, appears to form overnight in the volcanoes' summit craters, or calderas, and on sections of their rims and then to evaporate a few hours after sunrise.

While the frosty layer is exceptionally thin, it covers an enormous area. Scientists calculate that in the more frigid Martian seasons, 150,000 tonnes of water, equivalent to 60 Olympic swimming pools, condense daily on the tops of the towering mountains.

"It's the first time we've discovered water frost on the volcano summits and the first time we've discovered water frost in the equatorial regions of Mars," said Adomas Valantinas, a planetary scientist at the University of Berne in Switzerland and Brown University in the US.