(CN) — Astronomers detected water-based frost on the peaks of ancient Martian volcanoes during cold mornings, highlighting the possibility of localized atmospheric circulation over these massive volcanoes.
This discovery, published Monday in Nature Geoscience, suggests a more active exchange of water between the Martian surface and atmosphere than previously theorized.
"Water in its solid form (frost) can be found even in dry equatorial areas,” said Adomas Valantinas, of the Department of Earth, Environmental and Planetary Science of Brown University and a study co-author. “This signifies that microclimates can exist on Mars and that the Mars water cycle is more dynamic than previously thought."
The Tharsis rise — a plateau within Mars's tropical latitudes — hosts some of the solar system's largest volcanoes, including Mars’s tallest volcano, Olympus Mons.
These volcanoes appear inactive, yet spacecraft have detected water ice clouds and elevated levels of water vapor in the atmosphere above the Tharsis plateau. According to astronomers, this may be a sign of an active water cycle in this region, despite the typically dry and harsh conditions at the Martian tropics.
"Tharsis volcanoes create large topographic highs where high altitude atmospheric water vapor can precipitate in the form of frost," said Valantinas in an email interview.
Valantinas and his colleagues analyzed images from the European Space Agency's Trace Gas Orbiter, identifying ice deposits on the summits and caldera floors of Olympus Mons.
These frost deposits appear only in the early Martian morning during colder seasons. Climate model simulations showed that surface temperatures were consistent with the frost being composed of water rather than carbon dioxide, a conclusion supported by other spacecraft data analyses.
"We used climate models to simulate the thermodynamic conditions of the surface, indicating the presence of water frost. Additionally, spectral observations favor H2O over CO2 frost," Valantinas said.
The researchers estimate that the total mass of frost forming on the Tharsis volcanoes is about 150,000 tons of water ice. This amount, though small compared to the total water vapor in the Martian atmosphere, suggests a significant daily exchange of water between the surface and atmosphere during Mars's cold seasons.
These findings could mean that other regions of the planet may also harbor hidden reservoirs of water ice, furthering the mystery surrounding the Red Planet's climatic and geological past.
"This present-day phenomenon may have been more pronounced in the past when Mars had a thicker atmosphere," Valantinas said. "Previous studies have shown that there may have been glaciers on these volcanoes. If true, this buried water ice may have preserved the past climate record and potential biosignatures."
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