Three underground lakes have been identified near the south pole of Mars.

Scientists have also confirmed the existence of a fourth lake – the presence of which was indicated in 2018

Liquid water is vital to biology, so it will be of interest to researchers studying the possibility of life elsewhere in the solar system.

However, lakes are considered to be extremely salty, making it difficult for any microorganisms to survive in them.

The thin atmosphere of Mars means that the presence of liquid water at the bottom is an invisible impossibility. However, water may be liquid below ground.

The latest discovery was made using data from a radar device on the European Space Agency’s (ASA) Mars Express spacecraft, which has been orbiting the Red Planet since December 2003.

In 2018, researchers used data from Marsis radar to report signs of a dense polar cap formed by a layer of ice and dust, a 20-kilometer-wide surface lake located 1.5 kilometers under the south polar layer deposits of Mars.

However, that research was based on 29 observations collected by Marsis between 2012 and 2015. Now, a team including many of the same scientists in the 2011 study analyzed a larger dataset of 134 radar profiles involved between 2010 and 2016.

“We have not only confirmed the position, scope and strength of the image from our 2018 study, but we have found three new bright regions,” said Elena Petinelli, co-author of the University of Roma Tre in Italy. “

“The main lake was surrounded by a shorter body of liquid water, but due to the technical features of the radar and its distance from the Martian surface, we are unable to determine whether these are connected.”

The team borrowed a technique commonly used in radar sound investigations of sub-glacial lakes in Antarctica, Canada and Greenland, adopting the method of analyzing data from Mars.

Sebastian Loro, co-author of the University of Roma Tray, said: “The explanation that best fits all available evidence is that high-intensity reflections (from Mars) come from an expanding pool of liquid water,” said Sebastian Loro, co-author from Roma Tre University. .

At this depth there is not enough heat to melt ice, so scientists believe that liquid water must have a high concentration of dissolved salts. These chemical salts (unlike the ones we scatter in our chips) can significantly reduce water coagulation.

Indeed, recent experiments have shown that dissolved saline water of magnesium and calcium perchlorate (a chemical compound containing chlorine bound by four oxygen) may contain liquids at a temperature of -123C.

“These experiments have shown that brines can persist at temperatures in the Martian polar region (below the freezing temperature of pure water) and even for geologically significant periods,” said co-author Graziela Caprelli, from the University of Southern Queensland, Australia.

“Therefore we believe that the formation of sub-ice water beneath the ice pole caps and any process of persistence requires a higher salinity of the liquid.”

How salty these Martian pools are depends on whether life can survive in such a situation. On Earth, only very specific types of bacteria, known as halophils, can survive in the salinity of water.

Roberto Orosi, chief scientist at the Marsis Experiment, said: “Although the existence of a single sub-glacial lake can be attributed to exceptional conditions such as the presence of volcanoes under ice sheets, the discovery of the entire system of lakes suggests that their formation is relatively simple and common. The lakes probably existed for most of Mars’ history.

“Because of this, if Mars had a dense atmosphere, a mild climate, and the presence of liquid water at the bottom, they would still be able to retain any traces of life as early as Earth.”