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Near the Martian equator, the remains of a relatively modern glacier have just been identified. Under this relict glacier could have been ice water at shallow depths, something to take into account in the next steps of human exploration of the red planet.

Around the Martian water

The water of Mars is one of the most interesting topics in the study of the solar system. The topography of the red planet indicates that many of its accidents were caused by the flow of water in the past. Remember that, in the current conditions of the planet, liquid water does not subsist on the surface because, when it changes phase, the surface ice sublimates passing directly to the gas phase.

Therefore, a small amount of water vapor remains in the Martian atmosphere (around 0.01%), but there are multiple indications of ice in the subsoil. Locating and characterizing these bodies of water ice is a task of the greatest interest because these are the most promising places in the search for life on the small planet.

Relict glacier

The remains of a glacier have just been identified by researchers from the SETI Institute and the Mars Institute under the coordination of Pascal Lee, a member of those institutions. To do this, scientists analyzed very detailed data obtained by the HiRISE high-resolution camera on NASA's Mars Reconnaissance Orbiter (MRO).

Relict glacier topographyNASA/MRO/Lee et al.

In the images, they detected light-toned deposits (known as LTDs) that are usually composed of sulfate-like salts. The deposits, together with the numerous cracks in the terrain and the moraine bands, indicate that we are facing a relatively modern glacier that has not undergone major transformations throughout the geological history of Mars, what we call a 'relict' glacier.

Ice and volcanoes

The new glacier is about 6 kilometers of lake and about 4 kilometers wide. Its surface elevation ranges between 1.3 and 1.7 kilometers. It is located very close to the Martian equator (only 7 degrees south latitude), east of Noctis Labyrinthus.

Noctis Labyrinthus siteNASA

This entire region of Mars has undergone intense volcanic activity. A mixture of volcanic ash, pumice and lava blocks abounds throughout the area. When, in their day, these pyroclastic materials, ejected by the volcanoes, came into contact with the ice of the glacier, chemical reactions occurred that gave rise to a kind of crust of salts that we observe deposited today, but that at that time was on the surface of the glacier, forming an interface layer between the ice and the volcanic material. This saline crust preserved the amount and morphology of the ice underneath that gave rise to crack fields and moraine bands.

Over time, erosion removed much of the volcanic materials and the sulfate layer ended up being exposed. The entire area of the glacier, including the salt layer and the remaining volcanic materials, has very few impact craters and, therefore, must be geologically young. There are other remains of young glaciers at high Martian latitudes, but those that were known until now at low latitudes were very old. This new glacier confirms that there was also recent glacial activity near the Martian equator.

The importance of Ecuador

In the current conditions of Mars, some ice remains on the surface, especially at high latitudes, but water ice cannot remain stable near the equator. As noted above, the water that may have been in this area has been able to sublimate (become gaseous). But there is also the possibility that some of this water has seeped into the subsoil and has been trapped shallow under the salt crust.

A similar situation can be found on Earth, specifically in the salt flats of the Altiplano in South America. There, some old glacier has been protected, and has not melted, thanks to the protection offered by the layer of salts, of light color, which reflects solar radiation well.

If it is confirmed that there is ice preserved at shallow depths in the low Martian latitudes, this will have important implications for the future of the exploration of the red planet. Until now, the most promising places to find ice were located at high latitudes, in colder environments that, therefore, are more difficult for the possible work of humans and robots. The possibility of finding ice near the equator, in warmer environments, would facilitate working conditions.

But, in my opinion, there is still work to be done to determine unambiguously whether ice exists under this relict glacier and, if so, to estimate its quantity. In any case, the study of these regions with deposits of light-colored salts offers new opportunities to continue advancing in the great adventure of the exploration of our sister planet.

The work of Parcal Lee and collaborators has been published at the 54th LPSC Lunar and Planetary Science Congress 2023 held in Texas (USA) just a few days ago; the article is entitled "A relict glacier near Mars' equator: evidence for recent glaciation and volcanism in eastern Noctis Labyrinthus" and can be consulted at this link.

Rafael Bachiller is director of the National Astronomical Observatory (National Geographic Institute) and academician of the Royal Academy of Doctors of Spain.

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