Key Takeaways:
  • Massive Martian volcanoes sport a surprising feature – thin water frost appearing each morning on their peaks.
  • This discovery marks the first detection of water ice at the Martian equator, previously thought too hot for such formations.
  • Cold volcanic craters trap moisture-laden winds, creating a microclimate suitable for brief frost formation.
  • Though the icy film is incredibly thin, it covers a vast area, potentially accumulating enough water to fill dozens of Olympic pools daily.
  • Finding water on Martian volcanoes adds another layer to the planet’s water cycle, potentially aiding future human missions seeking resources.
The volcanoes along Mars’ equator are massive and imposing, with some peaks towering over twice the height of Mount Everest. The tallest, Olympus Mons, is the same width as France. Now, a new discovery adds to the mountains’ allure: early morning frost. According to a study published Monday in the journal Nature Geoscience, a winter frost periodically covers large patches of Mars’ Tharsis region, which is home to a dozen volcanoes—providing the most recent evidence of water on Mars and the first sighting of water at the planet’s equator. Some craters on the summits of volcanoes are coated in water frost for a few hours each morning, before sunlight strikes the equator directly. This icy film is thinner than a human hair, but it covers such a large area that researchers estimate the amount of water accumulating at the peaks each day could fill 60 Olympic-sized swimming pools.
A simulated perspective of Olympus Mons, the tallest volcano in the solar system, with water frost at its peak. ESA / DLR / FU Berlin (A. Valantinas)
“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 Ian Sample of the Guardian. “It could be related to atmospheric climate processes that were operating earlier in Martian history, maybe millions of years ago.” Astronomers discovered the frost while analyzing approximately 30,000 high-resolution color images of Mars taken by the European Space Agency’s Trace Gas Orbiter. The international team confirmed that the images were of frozen water, not carbon dioxide, which can look similar, by calculating that the volcanoes’ temperatures were too high for carbon dioxide to freeze. Researchers already knew that the planet’s northern and southern polar ice caps contained water ice, and this new discovery adds another location 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.
A map of Mars’ Tharsis region, featuring some of the planet’s largest volcanoes. NASA / MGS / MOLA Science Team, FU Berlin
Previously, scientists believed Mars’ equator was too hot and the atmosphere too thin to support frozen ice. However, the discovery of frost indicates a more nuanced water cycle, made possible by a microclimate on volcanoes. Mountain winds carry moist air into craters known as calderas, which are cool enough to condense during certain seasons. This process is “decidedly Earth-like,” according to Colin Wilson, project scientist for the Trace Gas Orbiter. According to the ESA, the discovery was made with both intention and luck. Most other Mars orbiters are synchronized with the sun, so they don’t see the planet’s equator until the afternoon, when the frost has melted away. Mars also has a limited, seasonal window in which frost can form. The researchers were looking for frost in other equatorial regions for a different project and were surprised to discover it on volcano peaks.
Four images, captured by the ESA’s Trace Gas Orbiter, show evidence of water frost on Ceraunius Tholus, a volcano on Mars. ESA / TGO / CaSSIS
Experts believe that water discoveries have significance as space agencies prepare to send humans to Mars.
Olympus Mons, seen from above, with water frost on its peak. ESA / DLR / FU Berlin (A. Valantinas)
“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,” says John Bridges, a planetary scientist at the University of Leicester in England who was not involved in the study. The Trace Gas Orbiter, which launched in 2016, studies the chemistry of Mars’ atmosphere while orbiting the planet. It is the first phase of the ESA’s ExoMars Program, with the simple goal of determining whether 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.
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