NASA/ESA/THE HUBBLE HERITAGE TEAM/STSCI/AURA
Hidden beneath the icy surface of the south pole of Mars, is a large lake of liquid water 20 kilometers in diameter, the first found on the Red Planet. The finding, made by a team of Italian astronomers from images of the European Mars Express orbiter, is published in the journal of “Science” and has been published by the Italian Space Agency in Rome. As they explain, this very cold body of water is brackish, a habitat not very kind to life. However, scientists say it resembles the subglacial reserves of Antarctica, where they have found simple organisms.
Billions of years ago, Mars harbored seas and rivers that today are ravines and canals as vestiges. But its atmosphere thinned and cooled and, at present, the liquid water on its surface seems destined to evaporate. The water survives frozen in the polar ice caps or in underground ice deposits, areas that are mapped by the Marsis instrument (Mars Advanced Radar for Subsurface and Ionosphere Sounding) aboard the European Mars Express probe. This instrument sends radar pulses that penetrate the terrain and blocks of ice it then measure the amount of time it takes to reflect back to the spacecraft and with what force. The reflected echoes provide scientists with information about what lies beneath.
USGS ASTROGEOLOGY SCIENCE CENTER/ARIZONA STATE UNIVERSITY/ESA/INAF/DAVIDE COERO BORGA
Between May 2012 and December 2015, Roberto Orosei’s team, from the National Institute of Astrophysics in Bologna, used Marsis to inspect a region called Planum Australe, located on the south pole of Mars. In 29 passes, it probed an area that exhibited a very abrupt change in its brightness. In addition, the analysis of the echoes showed that it has a high dielectric constant, a characteristic similar to that of aqueous materials. Researchers are convinced that it is a lake that extends about 20 kilometers and is located approximately 1.5 kilometers below the surface of the ice. If they are right, it would be the first time that a stable body of liquid water on Mars is observed.
The Pickle
To start off, the temperature of the Martian lake is around -68ºC, below the freezing point of pure water. “Under these conditions, liquid water can only be brackish, since the salts reduce the freezing point,” explains Anja Diez, a glaciologist from the Norwegian Polar Institute, who works in Antarctica and writes a related article in” Science.” Indeed, the dissolved salts of magnesium, calcium and sodium, which are known to be present in Martian rocks, could dissolve in the water to form a brine. Together with the pressure of the superimposed ice, the melting point is reduced, which allows the lake to remain liquid, as it happens on our planet. “For example, in the Dry Valleys (Antarctica) a brine lake has been found. However, the concentration of salt in the water is much lower than what is expected for Mars, “says the researcher.
As for the depth of the lake, it is estimated to be at least one meter, although Diez points out that it is impossible to really know for sure, since the radar data only provides images of the surface from the body of water. What is considered feasible is that there are more Martian lakes like this one, which could be revealed in the future with new studies and better measurements. “This is just a small area of study; It is an exciting prospect to think that there could be more of these underground bags of water in other places, yet to be discovered,” stresses Orosei. As he explains, to know more about the new discovered lake and find direct evidence of its existence, “it would be necessary to send robots there that drill 1.5 kilometers deep, but this is a technology that has not yet been developed.” If life ever existed on Mars it still remains to be seen.
