Another milestone for space exploration.
The ESA Mars Express probe, using radar surveys, has in fact discovered the presence of a lake of liquid water, with a diameter of 20 km, about 1.5 km below the frozen surface of the south pole of Mars.
A group of researchers led by Roberto Orosei, of INAF, has carried out the study of radar surveys obtained by the Marsis instrument (Mars Advanced Radar for Subsurface and Ionosphere Sounding), of Italian construction, of the Mars Express Orbiter.
The Marsis instrument is an innovative instrument, operating at a frequency between 1.5 and 5 MHz, able to penetrate up to 5 km of depth, where other radars can not reach. By studying the data obtained in the data obtained over twelve years by Marsis, along different orbits and at various times of the year, the scientists have identified a restricted area in the south pole of Mars highly reflective of the surrounding areas.
Various Italian institutions have contributed to this discovery: the ASI, the Roma Tre University, the Chieti-Pescara D’Annunzio University, the CNR and La Sapienza of Rome.
But how does liquid water exist under the surface of Mars? Mainly for two reasons. The melting point of the water is not only influenced by temperature, but also by pressure. A 1.5 km iced crust acts both as an insulator, thus raising the water temperature, and with its mass causes strong pressure. But it is not enough, and scientists are sure that the water in this lake contains a mixture of salts that act as antifreeze.
The discovery comes about 30 years after the theory of Stephen Clifford, who had already hypothesized the presence of liquid water under the ice caps of Mars.
That the liquid water flowed abundantly on Mars in the past is now certain, thanks to the repeated analysis on the morphology of the planet’s surface and the geological analysis of the samples. That there were traces of liquid water in the present, in part it was already known, in the form of water vapor or traces of brackish water. But, for the first time, scientists have discovered a stable and large mass of liquid water.
And speaking of this, as Roberto Orosei commented:
The great dilemma was therefore to determine where all that water was. Much of this was carried away by the solar wind, which swept the one that gradually evaporated from the surface of the water. Another significant portion is deposited in the form of ice in the caps, especially the north, and in the layers close to the surface or is bound to the ground in the permafrost. But one part must have been trapped in the depths and could still be in the liquid state.