For the first time, deposits of frozen water have been detected in the colossal volcanoes of Mars near the equator of the red planet, which are the largest mountains in the solar system.
The international team led by the University of Bern used high-resolution color images from the CaSSIS Martian camera, aboard the European Space Agency’s ExoMars Trace Gas Orbiter. Understanding where water can be found and how it is transported is relevant to future missions to Mars and possible human exploration. The study has just been published in the journal Nature Geoscience.
The frost was detected on the tops of the highest mountains on Mars, the Tharsis volcanoes. These volcanoes are the tallest mountains in the solar system, with Mount Olympus rising up to 26 km above the surrounding plains. This frost formation was not expected because these mountains are located at low latitudes near the equator of Mars.
“At these low latitudes, high amounts of sunlight tend to keep surface temperatures high. Therefore, we did not expect to find frost there,” says lead author Dr. Adomas Valantinas in an ESA statement. Additionally, Mars’ thin atmosphere is not effective at cooling the surface, so high-altitude surfaces can become as hot as low-altitude ones at midday, unlike on Earth.
MORNING FROST DEPOSITS
Valantinas explains: “Upward winds bring air containing water vapor from lowlands and this air cools as it reaches high altitudes, causing condensation. This is a familiar phenomenon on both Earth and Mars.” The same phenomenon causes Mount Arsia’s surprising elongated cloud, and the new study shows that it also leads to morning frost deposits on the Tharsis volcanoes.
“As we could see in the CaSSIS images, the thin frosts are only present briefly, for a few hours around dawn, before evaporating with sunlight,” continues Valantinas.
To identify the frost, Valantinas and the team analyzed more than 5,000 images taken by the CaSSIS Martian camera in Bern. Since April 2018, CaSSIS has provided observations of local dust activity, seasonal changes in CO2 ice deposits, and the existence of dry avalanches on Mars.
Thomas says: “The fact that we can now detect nocturnal water frost deposition on Mars at visual wavelengths and with high resolution is further evidence of the impressive scientific capabilities of the Bern camera system.”
The discovery was validated using independent observations from the High Resolution Stereo Camera (HRSC) on board ESA’s Mars Express orbiter and the NOMAD (Nadir and Occultation for Mars Discovery) spectrometer on board TGO.
Ernst Hauber, a geologist at the DLR Institute for Planetary Research (DLR-Institut für Planetenforschung) in Berlin and co-author of the current study, says: “This study clearly demonstrates the value of different orbital resources. By combining measurements from various instruments and models, we can “Improve our understanding of surface-atmosphere interactions in a way that would not be possible with a single instrument.”
According to Hauber, the results also show the importance of long-term monitoring of planetary processes, since some phenomena only become evident by comparing multiple measurements over time.
Despite being thin (probably only a hundredth of a millimeter thick, as thick as a human hair), the frost patches cover a vast area. “The amount of frost represents about 150,000 tons of water that are exchanged between the surface and the atmosphere every day during the cold seasons, the equivalent of about 60 Olympic swimming pools,” explains Valantinas.
“Understanding where water can be found and how it moves between reservoirs is relevant to many aspects of Mars exploration,” says Thomas.
“Of course, we want to understand the physical processes involved in the climate of Mars. But, in addition, understanding the water cycle on Mars is also of great importance to establish key resources for future human exploration and to limit past or present habitability “, concludes Valantinas.
