Mars has large underground ice deposits in the polar regions, but also near the equator. If this phrase surprised you, it shouldn’t, because it’s been known for more than a decade. But we now know that some of these deposits are much larger, up to 3.7 kilometers thick. Let us remember that news on Martian ice is recurrent since already in the 1970s, images from the Mariner 9 and Viking 1 and 2 probes demonstrated the presence of permafrost in vast areas of the planet due to the conformation of the material found around some craters. . But the extent of that ice was unknown until 2001, when NASA’s Mars Odyssey probe – which, incredibly, is still functioning – 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 surprising.
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, data from Mars Odyssey was difficult to interpret, and the precise amount of ice remained a matter of debate. It was necessary to send probes equipped with radar that would allow them to reach underground 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 functional). Mars Express has MARSIS radar (Mars Advanced Radar for probing the subsurface and ionosphere) and MRO radar SHARAD (Surface radar) and both studied the Martian subsurface 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 Southern Northern Hemisphere. According to radar, the massifs appeared to be formed by deposits of a thin, radar-transparent substance up to 2.5 kilometers thick. There was a possibility that they consisted of compacted dust or ash, that is, that they were equivalent to yardang terrestrial—, since MFF is the main source of dust on the planet. The massifs are given 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 kilometers.
Location of the MFF area (ESA/Mars Express). Geographical scope of the 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 gained from more than a decade of studying Mars using radar, new research concludes that the deposits are ice-rich and thicker than expected, up to 3.7 kilometers, a depth comparable to that of the polar ice cap. of the southern hemisphere. Its radar profile is similar to that of the Martian polar ice caps, which alternate layers of regolith with different proportions of water ice with drier ones (and some carbon dioxide ice deposits). MARSIS had already shown that equatorial MFF deposits have the same dielectric properties as polar deposits, but now it was also possible to resolve a layered structure similar to that found at the poles. Equatorial MFF deposits are enormous and, depending on their proportion of ice, once melted they could 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 basins could 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 surface 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 northern polar ice 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 able to better discern the separation between different layers, but only up to about 800 meters underground. Of course, unlike other areas with underground ice near the equator, these ice sheets will not be easily accessible for use by manned or unmanned missions, as they are covered by hundreds of meters of dust deposits of thickness including between 300 and 600 meters. The question many may ask is: how is it possible that there are enormous ice deposits 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 this quantity). We do not know the exact answer, but everything indicates that the cause is to be found in the periodic changes in the inclination of the planet’s rotation axis, which have caused notable climate changes not only on a time scale of millions of years, but also in 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).
The Medusae Fossae area seen from 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, budget shortfalls due to development of the MSR sample return mission caused this mission to be delayed until next decade). As we see, ice on Mars continues to get people talking.
Lucus Planum, one of the massifs of the Medusae Fossae in an image from the MRO (NASA) CTX camera.
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2024-01-18 23:42:12
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