Recently, the ESA radar group Mars Express received exciting information: the instruments indicate a reservoir of liquid water buried 1.5 km below the southern polar ice of the Red Planet.
In the period 2012-2015. Mars Express made multiple passes in the studied 200-kilometer region of Planum Australe (South Polar Plain), beating radio waves along the surface of the planet and recording the characteristics of the reflected signal using the enhanced MARSIS rad.
Radar traces on the surface are shown in the image and have color coding corresponding to the signal power reflected from the signs below the surface. The brightest ones are colored blue, and data from several overlapping orbits define a zone 20 km wide. It corresponds to a triangular shape to the right of center.
Under the spot of repeating layers of ice and dust, at a depth of 1.5 km, there is a base layer with radar signals inherent in liquid water. Despite the low freezing temperatures on Mars, it can be maintained in a liquid state in the presence of salts.
Once upon a time, the water quietly flowed over the Martian surface, but is now devoid of stability. Detection of liquid water hidden beneath the surface is necessary to understand the evolution of Mars, the history of water on a nearby planet, and its habitability.