On early winter mornings, a thin layer of ice forms in craters atop the Red Planet’s towering peaks, near its equator, according to a new study
The volcanoes along Mars’ equator are massive, imposing features, with some peaks towering more than twice the height of Mount Everest. Olympus Mons, the tallest, is as wide as France. Now, a new discovery adds to the mountains’ intrigue: the presence of early morning frost.
According to a study published Monday in the journal Nature Geoscience, a winter frost periodically covers extensive patches of Mars’ Tharsis region, home to a dozen volcanoes—providing the latest evidence of water on Mars and the first sighting of water at the planet’s equator.
For a few hours each morning, before sunlight directly strikes the equator, some craters at the volcanoes’ summits are coated in a layer of water frost. This icy film is thinner than a human hair, but it covers so much area that the amount of water accumulating daily at the peaks, researchers estimate, could fill 60 Olympic-sized swimming pools.
“What we’re seeing could be a trace of a past Martian climate,” Adomas Valantinas, a planetary scientist at the University of Bern in Switzerland, tells the Guardian’s Ian Sample. “It could be related to atmospheric climate processes that were operating earlier in Martian history, maybe millions of years ago.”
Astronomers spotted the frost when analyzing roughly 30,000 high-resolution color images of Mars captured by the European Space Agency’s (ESA) Trace Gas Orbiter. The international team confirmed the pictures were indeed of frozen water—not of carbon dioxide, which can appear similar—by calculating that the volcanoes’ temperature was too hot for carbon dioxide to freeze.
Researchers already knew the planet’s northern and southern polar ice caps hosted water ice, and the new finding adds another site to the map of Mars’ water.
“This is quite exciting, because it tells you how dynamic Mars’ water system is, but also how water can be found in different amounts basically everywhere on Mars,” Valantinas tells New Scientist’s Alex Wilkins.
Scientists previously thought Mars’ equator was too hot—and its atmosphere there too thin—to support frozen ice. But the finding of frost is evidence of a more nuanced water cycle, one made possible by a microclimate atop volcanoes. There, mountain winds carry moist air into craters called calderas that are, during certain seasons, cool enough for condensation to occur.
This process is “decidedly Earth-like,” as Colin Wilson, project scientist for the Trace Gas Orbiter, says in an ESA statement.
The discovery was made with a combination of intention and luck, according to the ESA. Most other Mars orbiters are synchronized with the sun, which means they don’t observe the planet’s equator until the afternoon, when the frost has already melted away. Mars also has only a narrow, seasonal window when frost can form. The researchers were looking for frost in other equatorial regions for a different project and were surprised when they found it on volcanoes’ peaks.
As space agencies look toward sending humans to Mars, discoveries of water are crucial, experts say.
“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,” John Bridges, a planetary scientist at the University of Leicester in England who was not involved in the research, tells the Guardian.
The Trace Gas Orbiter, launched in 2016, studies the chemistry of Mars’ atmosphere as it orbits the planet. It is the first part of the ESA’s ExoMars Program, which has the straightforward goal of discovering if life has ever existed on Mars. The Rosalind Franklin Rover, the program’s second act, set to launch in 2028, will land on the planet’s surface, roam around and study Martian rocks.
Frost Seen on Olympus Mons for the First Time
It’s been known for years that there are large quantities of water ice locked up in the Martian poles. Around the equator however it is a barren dry wasteland devoid of any surface ice. Recent observations of Mars have discovered frost on the giant shield volcanoes but it only appears briefly after sunrise and soon evaporates. Estimates suggest that 150,000 tons of water cycle between the surface and atmosphere on a daily basis.
The polar caps of Mars have been the subject of many studies in particular, since the discovery of water ice in 2008. They are permanent but vary in size with the seasons. During the winter and in complete darkness, the surface chills allowing gas in the atmosphere to deposit on the surface as great bit chunks of carbon dioxide ice. Then the poles are exposed to sunlight again the frozen carbon dioxide sublimes straight back into a gas.
Aside from the carbon dioxide, the poles are mostly composed of frozen water ice. The carbon dioxide deposits are relatively thin compared to the water ice, only about 1metre thick over the north pole. The south pole has a more permanent carbon dioxide cap about 8 metres thick.
A team of planetary scientists led by Adomas Valantinas, a postdoctoral fellow at Brown University who led the work as a PhD student at the University of Bern have detected water frost on top of the Tharsis volcanoes on Mars. These volcanoes are among the tallest on the planet and indeed one of them; Olympus Mons is the tallest in the solar system.
The frost was discovered using high-resolution images from the Colour and Stereo Surface Imaging System (CaSSIS) which is just one of the instruments on the ESA Trace Gas Orbiter. The discovery was validated using further independent observations from the High Resolution Stereo Camera on Mars Express Orbiter.
This is the first time water frost has been discovered in the vicinity of the planet’s equator calling for a rethink of the planets climate dynamics. Until now, we thought it was quite unlikely for frost to form around the equator due to the levels of solar radiation and the thin atmosphere. The conditions mean the surface temperatures can reach reasonably high temperatures, too high for frosts to form even at the top of the volcanoes.
The study seems to show that frost is only fleeting present for a few hours after sunrise before the high temperatures cause it to evaporate in the solar radiation. It is important to note that even though the frost is only a very thin later (just about the width of a human hair) it is thought that there is something like 150,000 tons of water that cycles between the surface and the atmosphere every day.
The frost the team have discovered deposits in the caldera of the volcanoes. These hollows are the openings at the summit of the volcano where eruptions have previously exploded out through the crust. It is now thought that there are unusual microclimates at the tops of the volcanoes which allows the thin layers of frost to form.
The discovery means we need to model how the frost forms to get a real understanding of where water might exist on Mars, how it moves and how it interacts with the atmosphere.
Space Today 