ESA’s Mars Express spaceships have discovered several ponds of liquid water that are buried under the ice in the southern polar region of Mars. The spacecraft’s radar instrument, MARSIS (Mars Advanced Radar for Underground and Ionospheric Probing), revealed an underground reservoir in 2018, buried about 1.5 km under the ice. Now, when more data is taken into account and analyzed in other ways, three new ponds have been discovered. The largest underground lake measures around 20 x 30 km and is surrounded by several smaller ponds. It is believed that the water is very salty in order to keep it liquid in cold temperatures.
Mars was once warmer and more humid, and water flowed across the surface, much like it did on early Earth. While it is not possible today for water to remain stable at the surface, the new result opens up the possibility that an entire system of ancient lakes exists underground, perhaps millions or even billions of years old. They would be ideal places to look for evidence of life on Mars, albeit very difficult to get to.
Subglacial lakes are also known on Earth, such as the Vostok Sea in Antarctica. They may host unique ecosystems and provide useful analogies for astrobiologists studying how life can survive in extreme environments. The techniques used to analyze radar data on Mars are similar to those used to study subglacial lakes in Antarctica, Canada, and Greenland.
Reference: “Several subglacial waters below the south pole of Mars revealed by new MARSIS data” by Sebastian Emanuel Lauro, Elena Pettinelli, Graziella Caprarelli, Luca Guallini, Angelo Pio Rossi, Elisabetta Mattei, Barbara Cosciotti, Andrea Cicchetti, Francesco Soldovieri, Marco Cartacci , Federico Di Paolo, Raffaella Noschese and Roberto Orosei, September 28, 2020, Natural astronomy.
DOI: 10.1038 / s41550-020-1200-6