The equatorial region of Mars home to the highest volcanoes in the world Solar systemwhich – in addition to being as tall as three Mount Everests in some cases – likely hide an unexpected icy phenomenon, according to a new study.
The biggest of them – Olympus Mons – is 26 kilometers high and an impressive 602 kilometers in diameter, being around 100 times larger than the largest volcano on Earth, Mauna Loa, in Hawaii. In fact, the entire chain of Hawaiian islands could fit inside the Martian volcano, according to NASA (United States space agency).
These giants are topped by large calderas – bowl-shaped depressions caused by the collapse of the top of the volcano after an intense eruption.
The colossal size of the calderas – up to 121 kilometers in diameter – creates a special microclimate inside them. Using cameras installed on probes orbiting Mars, researchers observed the formation of morning frost inside calderas for the first time.
“Deposits are forming on the caldera floor, but we also see some frost on its edge. We also confirm that it is ice and probably water,” said Adomas Valantinas, a postdoctoral researcher at Brown University (United States) who made the discovery as a doctoral candidate at the University of Bern, Switzerland, and lead author of the study.
“It’s significant because it shows us that Mars is a dynamic planet, but also that water can be found almost everywhere on the Martian surface.”
5 thousand images
The team of more than two dozen researchers detected frost on four volcanoes: Arsia Mons, Ascraeus Mons and Ceraunius Tholus, as well as Olympus Mons, according to the study published Monday in Nature Geoscience magazine.
The deposits are extremely thin — just a hundredth of a millimeter thick, or one-sixth of a human hair, according to Valantinas — but they are spread over such a large area that they are equivalent to a significant amount of water. “Based on rough estimates, that’s about 150,000 metric tons of water ice, the equivalent of 60 Olympic-size swimming pools,” he said.
To observe the deposits, the team first analyzed around 5,000 images taken by CaSSIS — the Color and Stereo Surface Imaging System at the University of Bern — a high-definition camera that has been photographing Mars since 2018. It is among the instruments aboard the ExoMars Trace Gas Orbiter, a spacecraft launched in 2016 as a collaboration between the European Space Agency (ESA) and the Russian space agency Roscosmos.
“This is also the first discovery to come from CaSSIS, which is quite exciting,” said Valantinas.
The team validated their observations with two other instruments: NOMAD, a spectrometer also aboard the Trace Gas Orbiter, and HRSC, or high-resolution stereo camera, an older camera aboard ESA’s Mars Express orbiter, a spacecraft launched in 2003. .
Fortuitous discovery
Valantinas says the discovery had a degree of serendipity because he was originally looking for carbon dioxide frost but didn’t find any. The deposits have not been detected until now because they only form during the early morning hours and cooler months, making the observation window narrow.
However, it is unlikely that frost could ever be harvested by human astronauts on Mars. “It would be quite difficult, because although it is a large deposit, it is also very thin and ephemeral, meaning it is only present during the night and early morning, then sublimates back into the atmosphere,” Valantinas said.
The volcanoes are close to Mars’ equator, the hottest area on the planet, which makes the discovery of water particularly intriguing, Valantinas said.
“Mars is a desert planet, but there is water ice in the polar caps and there is water ice in the middle latitudes. Now we also have water frost in equatorial regions, and equatorial regions are generally quite dry. So this was quite unexpected,” he said.
He added that in the past, when Mars had a thicker atmosphere and a different climate, there may have been glaciers on these volcanoes. The team now wants to expand the search for frost to all of the more than a dozen named volcanoes on Mars.
A remarkable achievement
If humans ever explore the Red Planet, we’ll need to know where the water is, so the Martian water cycle is an important field of study, said John Bridges, professor of planetary sciences at the University of Leicester in the United Kingdom, who was not involved. of the study.
“This paper is a fantastic use of the CaSSIS camera on the ExoMars Trace Gas Orbiter, which captures both visible light and infrared light reflected from the Martian surface,” said Bridges, calling the results a “remarkable achievement.”
Additionally, the water cycle on Mars is nowhere near as active as it was billions of years ago, so it’s challenging to measure how water moves across the surface, noted J. Taylor Perron, the Cecil and Ida Green Professor of Earth Sciences. , Atmospheric and Planetary Science at the Massachusetts Institute of Technology (MIT). Perron was also not affiliated with the new research.
“If the frost on these volcanoes is confirmed to be water (and not carbon dioxide), it would be surprising,” he said.
Across the surface of Mars it is cold and dry, Perron added, but the area around the equator is drier and less cold than the poles, so it is one of the last places you would expect to see water frost. It would also raise the question, he concluded, of where the water vapor that forms frost comes from—from the volcanoes themselves, even if they are dormant, or from much further away, like the polar ice caps.
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