An article published in the journal “Geophysical Research Letters” describes the discovery of a kind of subterranean lake in Utopia Planitia on Mars. A team of researchers led by Cassie Stuurman of the Institute for Geophysics at the University of Texas, Austin, used the data gathered by the SHARAD instrument on the Mars Reconnaissance Orbiter (MRO) space probe to examine the subsoil of this basin located in the red planet’s northern hemisphere.
The Utopia Planitia basin was formed in the early history of Mars by the impact of an asteroid. It’s what remains of a crater with a diameter of about 3,300 kilometers (2,050 miles). Certain morphological characteristics of the area remind of the Arctic regions in Canada, where they’re indicative of the presence of ice in the ground. However, there was a big doubt about the possibility that in that great Martian basic the ice had evaporated millions of years ago because of the low atmospheric pressure.
The SHARAD (SHAllow RADar) instrument is a ground-penetrating radar developed by the Italian Space Agency and provided to NASA for the MRO space probe. The data of more than 600 passes above Utopia Planitia allowed to test the hypothesis of the presence of ice by finding the radar traces of an underground deposit that has a thickness between 80 and 170 meters (260 and 560 feet) composed between 50% and 85% of water ice mixed to dust and other rock particles.
The amount of water present is estimated to be a bit more than that existing in Lake Superior, the largest lake of the Americas. That water can exist in its solid state because it’s protected by a layer of soil which has a thickness between 1 and 10 meters (3 and 33 feet) so the ice never comes in contact with the atmosphere and therefore can’t sublimate.
That deposit was probably formed by the accumulation of snow in a period of Mars’ history when the planet’s axis was more tilted. In the course of the cycles that last 120,000 years the tilt varies more than twice with the result that the poles get heated and the ice gets transported to intermediate latitudes such as that of Utopia Planitia.
The discovery of water ice on Mars isn’t a surprise but the amount in the subsoil of Utopia Planitia is truly remarkable. The discovery of deposits of this kind can provide important information in understanding the environmental conditions evolution on the planet. It’s not clear why the ice is deposited in certain areas and not in others so every discovery is a piece of the Martian puzzle. For this reason, the analyzes of data collected by Sharad continue.
The area of Utopia Planitia has been the subject of interest for decades, so much that the Viking 2 mission’s lander touched down near the crater Mie within the great basin. Among the experiments conducted there were also some linked to the search for life forms. The results were contradictory and it wasn’t possible to draw firm conclusions but in time they’ve been reexamined a number of times and there are researchers who argue that in fact the results were positive, such as in a study published in April 2012.
The discovery of so much water revived the interest in Utopia Planitia and the hypotheses about the existence of life forms on Mars. There’s also a practical interest due to the fact that a manned mission on Mars will have to rely on some local resources and water is crucial. This means that Utopia Planitia has become even more a possible area for a human base.