2024-01-18 23:42:12
Mars has large underground ice deposits in the polar regions, but also near the equator. If this phrase has surprised you, it shouldn’t, because it has been known for more than a decade. But now we know that some of these deposits are much larger, with a thickness that can reach 3.7 kilometers. Let us remember that news regarding Martian ice has been recurring since in the 1970s, images from the Mariner 9 and Viking 1 and 2 probes demonstrated the presence of permafrost in large areas of the planet due to the shape of the material found around some craters. . But the extent of that ice was unknown until, in 2001, NASA’s Mars Odyssey probe—which, incredibly, still works—confirmed the existence of underground ice deposits using its neutron spectrometer. Although Mars Odyssey verified the presence of ice in the polar regions, it was the deposits near the equator that were a surprise.
Possible ice thickness of the MFF massifs according to Mars Express assuming a surface layer of dry deposits of 300 meters (ESA/Mars Express).
However, the Mars Odyssey data was difficult to interpret and the precise amount of ice remained a matter of debate. Probes had to be sent equipped with radar that would allow them to reach the subsoil in search of ice. In 2003 and 2005, ESA’s Mars Express and NASA’s MRO probes were launched, respectively (no less incredibly, both are still working). Mars Express has the MARSIS radar (Mars Advanced Radar for Subsurface and Ionosphere Sounding) and SHARAD radar MRO (Shallow Radar) and both have studied the Martian subsoil and the distribution of ice globally. One of the areas studied by these radars was the Medusae Fossae Formation (MFF), a series of strange and large massifs with an extension of almost 5000 kilometers located near the equator in a transition region between the rugged southern hemisphere and the plains of the South. North Hemisphere. According to radar, the massifs appeared to be formed by deposits of some thin, radar-transparent substance with a thickness of up to 2.5 kilometers. There was a possibility that they were made up of compacted dust or ashes—that is, that they were equivalent to the yardangs terrestrials—, as MFF is the main source of dust on the planet. The massifs receive the names Amazonis Mensa, Eumenides Dorsum, Lucus Planum, Aeolis Planum, Zephyria Planum and Gordii Dorsum, and their estimated volume ranged between 1.4 and 1.9 million cubic kilometres.
Location of the MFF area (ESA/Mars Express). Geographic extension of MFF. To the right is the Tharsis Plateau (MOLA/MRO/NASA/Ojha et al.). This is how the MARSIS radar sees the profile of the MFF massifs (ESA/CReSIS/KU/Smithsonian Institution).
Using additional data from the MARSIS radar and knowledge from more than a decade studying Mars using radar, new research concludes that the deposits are high in ice and are thicker than expected, up to 3.7 kilometers thick. a depth comparable to that of the polar cap of the southern hemisphere. Its radar profile is similar to that of the Martian polar caps, which alternate layers of regolith with different proportions of water ice with drier ones (and some deposits of carbon dioxide ice). MARSIS had already shown that equatorial MFF deposits have the same dielectric properties as polar deposits, but now it has also been possible to resolve a layered structure similar to that found at the poles. The equatorial deposits of MFF are enormous and, depending on their proportion of ice, once melted they might cover the entire Mars—I repeat, the entire planet—with a layer of water 1.5 to 2.7 meters deep (assuming the planet was perfectly spherical). Or, alternatively, the water from these reservoirs might fill the Earth’s Red Sea or the Great Lakes of North America (as an exercise I leave it to the reader to calculate how much this is in santiagobernabéus, sb, which is the unit of area, length and volume in the International Journalistic System). In Martian terms, these deposits, if confirmed, would contain half the water of the planet’s entire boreal polar cap.
Reconstruction of the upper layer of dry sediments above the ice (ESA/CReSIS/KU/Smithsonian Institution). Another map of Medusae Fossae (NASA/Thomas Matters et al.).
For this research, data from the MARSIS radar is crucial due to its ability to penetrate up to several kilometers deep, while SHARAD is capable of better discerning the separation between different layers, but only up to approximately 800 meters below the ground. Of course, unlike other areas with underground ice near the equator, these ice layers will not be easily accessible for use by manned or unmanned missions, as they are covered by hundreds of meters of dust deposits between 300 and 600 meters thick. The question that many may be asking is, how is it possible that there are huge deposits of ice on the equator of Mars? Because, although the red planet is much colder than Earth, this ice should not be there (or, at least, not in such quantity). We do not know the exact answer, but everything indicates that the cause must be sought in the periodic changes in inclination of the planet’s axis of rotation, which have caused considerable climate changes not only on a time scale of millions of years, but even in periods very short periods of just thousands of years (the Martian axis, currently with an inclination similar to that of the Earth, can reach inclinations of up to 60º, causing the formation of glaciers and other ice deposits at very low latitudes).
Medusae Fossae area as seen by Mars Express (ESA/DLR/FU Berlin). Eumenides Dorsum is the massif with the thickest ice deposit according to Mars Express (ESA).
It is not surprising that the precise study of the size, distribution and thickness of Martian ice deposits is one of the priorities of the scientific community, which is why NASA wants to send an orbiter equipped with a high-resolution radar, like the I-MIM mission (unfortunately, lack of budget due to the development of the MSR sample return mission has caused this mission to be delayed until the next decade). As we see, the ice on Mars continues to cause people to talk.
Lucus Planum, one of the Medusae Fossae massifs in an image from the MRO (NASA) CTX camera.
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