Mars Orbiters Discover 150,000 Tonnes Of Water Frost on Solar System Largest Volcano in The Martian Tropics

ESA’s ExoMars and Mars Express missions have identified water frost near Mars's equator, challenging previous assumptions about the Red Planet's climate.

This frost, found atop the towering Tharsis volcanoes, marks the first recorded instance of frost forming in such a region, previously thought impossible due to the planet's mix of sunlight and thin atmosphere keeping temperatures relatively high.

The discovery was first made by ESA’s ExoMars Trace Gas Orbiter (TGO) and subsequently confirmed by both another instrument on TGO and ESA’s Mars Express.

Lead author Adomas Valantinas, who discovered the frost as a PhD student at the University of Bern and is now a postdoctoral researcher at Brown University, expressed his astonishment:

“We thought it was impossible for frost to form around Mars’s equator, as the mix of sunshine and thin atmosphere keeps temperatures relatively high at both surface and mountaintop – unlike what we see on Earth, where you might expect to see frosty peaks. Its existence here is exciting and hints that there are exceptional processes at play that are allowing frost to form.” - Adomas Valantinas

Frost Formation on Mars's Tallest Volcanoes

The frost was observed on the Tharsis volcanoes, including Olympus Mons and the Tharsis Montes: Ascraeus, Pavonis, and Arsia Mons. These volcanoes are the tallest not only on Mars but in the entire Solar System, with Olympus Mons standing nearly three times the height of Earth's Mount Everest.

The frost appears only for a few hours around sunrise before evaporating in sunlight, forming a thin layer about as thick as a human hair and covering a vast area.

The amount of frost represents approximately 150,000 tonnes of water cycling between the surface and atmosphere daily during the cold seasons, equivalent to about 60 Olympic swimming pools.

Researchers propose that a unique microclimate within the calderas of these volcanoes, caused by peculiar air circulation patterns, allows frost to form.

“Winds travel up the slopes of the mountains, bringing relatively moist air from near the surface up to higher altitudes, where it condenses and settles as frost: - Nicolas Thomas, Principal Investigator of TGO’s Colour and Stereo Surface Imaging System (CaSSIS).

Implications for Mars Exploration

This discovery, the first of its kind at Mars's equator, provides new insights into the planet’s atmospheric dynamics and water cycle, crucial for future exploration and the search for signs of life.

The frost was spotted using TGO’s CaSSIS instrument and confirmed by TGO’s Nadir and Occultation for Mars Discovery (NOMAD) spectrometer and Mars Express’s High Resolution Stereo Camera (HRSC).

“We need an orbit that lets us observe a location in the early morning. While ESA’s two Mars orbiters – Mars Express and TGO – have such orbits and can observe at all times of day, many from other agencies are instead synchronized to the Sun and can only observe in the afternoon.” - Adomas Valantinas

Collaborative Success

The collaboration between ESA’s Mars orbiters was key to this discovery. TGO, in orbit since 2016, and Mars Express, exploring Mars since 2003, worked together to reveal these frost patches.

“Finding water on the surface of Mars is always exciting, both for scientific interest and for its implications for human and robotic exploration. This discovery is particularly fascinating as it showcases an Earth-like phenomenon on Mars.” - Colin Wilson, ESA Project Scientist for both ExoMars TGO and Mars Express

Understanding these processes enhances our knowledge of basic atmospheric and climatic behaviors on Mars.