Mars has just revealed a new secret: frost was found on the summit of its gigantic volcanoes, an unexpected discovery that will allow us to better understand the water cycle of the red planet, essential for future explorations.
The scene was captured by accident from Martian orbit by the Trace Gas Orbiter (TGO) probe of the European Space Agency (ESA) in the Tharsis dome, near the equator of Mars, describes a study published Monday in Nature Geosciences.
This vast and elevated region of about 5,000 km in diameter is home to immense volcanoes that have been extinct for millions of years. Among them is the largest in the solar system, the 22 km high Olympus Mons, three times the size of Everest.
Nobody expected to find frost in that place. “We thought it was impossible around the equator of Mars,” summarized Adomas Valantinas, lead author of the study that led to the discovery.
The strong sunlight and the very low atmospheric pressure “keep the temperatures quite high both at the summit and on the surface,” details Valentinas, a researcher at Brown University in the United States, in an ESA statement.
In the Tarshish region, temperatures can drop to -130 degrees Celsius at night, but they do not depend on altitude, “contrary to what happens on Earth, where one expects to see frozen peaks,” he explained.
The atmosphere of the Martian equator has a particularly low water content, making condensation difficult.
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“Other probes had observed frost but in more humid regions, such as the northern plains,” Frederic Schmidt, professor at Paris-Saclay University, one of the authors of the study, told AFP.
The thickness of a hair
The discovery was fortuitous. The TGO probe, which has been orbiting Mars since 2018, can observe its surface at any time of the day, revealed the paleontologist specialized in the ice of the solar system.
He was also able to capture images of the first rays of the sun. “We saw a bright, blue deposit, a particular texture that we only see at dawn and in the cold seasons,” she said.
The ice deposit was very thin, the thickness of a hair, but the amount of frost present on the summits of four volcanoes (Olympus Mons, Ascraeus Mons, Arsia Mons, Ceraunius Tholus) represents “150,000 tons of water circulating between the surface and the atmosphere every day, the equivalent of 60 Olympic swimming pools,” commented ESA.
How do you explain that? The authors of the study suggest the existence of a microclimate inside the volcanoes’ caldera, its vast circular craters.
The winds rise up the slopes of the mountains, “carrying relatively humid air from the surface to the highest parts, where it condenses and is deposited as frost,” according to Nicolas Thomas, co-author of the study.
“We observed this phenomenon on Earth and in other regions of Mars,” added the principal investigator of the TGO Surface Color and Stereoscopic Imaging System.
Modeling the process of frost formation should allow us to better understand the water cycle – its dynamics of movement between the surface, the atmosphere, the equator and the poles – “one of the best kept secrets” of the red planet, according to ESA.
This is an important step for future human and robotic explorations.
“We could recover water from frost for human consumption and launch rockets from Mars by separating oxygen and hydrogen molecules,” Schmidt said.
Being able to map the water on the Martian surface, which currently only exists in the form of vapor or ice, is also essential for the search for traces of life, the appearance of which would have been possible thanks to the presence of liquid water 3,000 and 3,500 million years ago. .
