Recent observations have revealed the presence of early morning frost on some of the largest mountains on Mars, specifically the colossal Martian volcanoes that rise up to three times the height of Mount Everest near the planet’s equator.
This discovery, documented in a study published in Nature Geoscience, marks the first time water frost has been detected in the equatorial regions of Mars. The frost appears as a thin dusting of ice, less than the thickness of a human hair, forming overnight in the summit craters (calderas) of these volcanoes and evaporating a few hours after sunrise.
Frost Formation and Detection
Researchers from Brown University and the University of Berne have calculated that in the colder months, about 150,000 tons of water, equivalent to 60 Olympic-size swimming pools, condense daily on the tops of these towering mountains.
The frost was detected using high-resolution color images taken by the European Space Agency’s Trace Gas Orbiter (TGO) and confirmed through additional spectrometer data and images from the Mars Express orbiter. The frost-covered areas appear bluish in the images, particularly in the caldera floors and some sections of the rims, while well-lit slopes remain frost-free.
The Tharsis region of Mars, a vast volcanic plateau near the equator, is home to a dozen large volcanoes, including Pavonis Mons and Olympus Mons, which are nearly nine and sixteen miles tall, respectively. These findings suggest that frost can form on these volcano tops despite the thin Martian atmosphere and relatively high daytime temperatures.
Adomas Valantinas, a planetary scientist at Brown University and lead author of the study, remarked, "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."
Insights into Mars' Atmospheric Conditions
This discovery provides significant insights into Mars' atmospheric conditions and its potential climatic history. Scientists believe that the formation of frost on these volcanoes could be related to atmospheric processes that operated earlier in Martian history, possibly millions of years ago.
Valantinas suggests that the phenomenon might be a remnant of a past climate cycle on Mars, indicating that the planet once experienced precipitation and maybe even snowfall on these volcanoes. "What we’re seeing could be a trace of a past Martian climate," Valantinas explained, adding, "It could be related to atmospheric climate processes that were operating earlier in Martian history, maybe millions of years ago."
The Role of Martian Winds
Valantinas hypothesizes that Martian winds might blow up the mountainsides, carrying moist air into the calderas where it condenses and settles as frost at specific times of the year. Modeling suggests that this frost is indeed water ice, as the temperatures at the peaks are not low enough for carbon dioxide frost to form. "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," Valantinas said.
Implications for Mars Exploration
The presence of water frost on Mars' volcanoes has implications for future exploration missions, especially those involving human exploration. Understanding the present-day water cycle on Mars, both in the atmosphere and near the surface, is crucial for future missions, as water will be a key resource. John Bridges, a professor of planetary sciences at the University of Leicester, emphasized, "Understanding the present day water cycle on Mars in the atmosphere and near surface will be important for future exploration missions including human ones where water will be the key in situ resource."