By studying the South Polar region of Mars, the MARSIS (Mars Advanced Radar for Subsurface and Ionospheric Sounding) radar of the Mars Express space probe has enabled the structure of the layered deposits of this region to be elucidated. For the first time in the history of planetary exploration, topographic maps of the Martian sub-soil have been produced, revealing considerable volumes of ice. The LPG (Grenoble Planetary Laboratory) (CNRS – Université Grenoble 1) has been closely involved in processing and analyzing data from the Marsis radar. These results were published on the website of the journal Science on March 15, 2007.
The Marsis low frequency radar has been designed so that its signals penetrate into the Martian sub-soil. Consequently, its radar signals can reach a depth of more than 3.7 km, which has made it possible to map the boundary between the layered deposits and the floor of the basin.
In addition, the study of the Marsis radar signal has revealed that the South Polar region of Mars, which has the shape of a giant dome of around 1000 km diameter, is mainly composed of ice. Another important result: highly variable distribution and depth of the ice deposits have been observed. In particular, a series of depressions of 50 to 200 km diameters and with a depth of around 1 km compared to the average level of the subsurface (sub-soil) have been identified at high latitudes. Thanks to the Marsis instrument, it has been possible to estimate the total volume of ice in this region at 1.6 million cubic kilometers. If this volume of ice was distributed in a uniform manner over the whole surface of the planet, Mars would be covered by 11 m of water.