Shafaq news/ Nature.com published Nature published a study in which it said that two years ago, planetary scientists reported the discovery of a large saltwater lake under the ice at Mars’s south pole, a finding that was met with excitement and some scepticism. Now, researchers say they’ve confirmed the presence of that lake—and found three more. 

The discovery, reported on 28 September in Nature Astronomy, was made using radar data from the European Space Agency’s (ESA) orbiting Mars Express spacecraft.

“We identified the same body of water, but we also found three other bodies of water around the main one,” says planetary scientist Elena Pettinelli at the University of Rome, who is one of the paper’s co-authors. “It’s a complex system

The team used a radar instrument on Mars Express called the Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS) to probe the planet’s southern polar region.

MARSIS sends out radio waves that bounce off layers of material in the planet’s surface and subsurface.

 The way the signal is reflected back indicates the kind of material that is present at a particular location—rock, ice or water.

For example, A similar method is used to identify subsurface glacial lakes on Earth. The team detected some areas of high reflectivity that they say indicate bodies of liquid water trapped under more than one kilometer of Martian ice.

The lakes are spread over about 75,000 square kilometers—an area roughly one-fifth the size of Germany. The largest, central lake measures 30 kilometers across, and is surrounded by three smaller lakes, each a few kilometers wide.

On the surface of Mars, the low pressure that results from the planet’s lack of a substantial atmosphere makes liquid water impossible. But scientists have long thought that there could be water trapped under Mars’s surface, perhaps a remnant of when the planet once had seas and lakes billions of years ago.

But the amount of salt present could pose problems. It’s thought that any underground lakes on Mars must have a reasonably high salt content for the water to remain liquid. Although this far beneath the surface there may be a small amount of heat from the interior of Mars, this alone would not be enough to melt the ice into water. “From a thermal point of view it has to be salty,” says Pettinelli.

Lakes with a salt content about five times that of seawater can support life, but as you approach 20 times that of seawater life is no longer present, says John Priscu, an environmental scientist at Montana State University.

 “There’s not much active life in these briny pools in Antarctica,” says Priscu, whose group studies microbiology in icy environments. “They’re just pickled. And that might be the case

The presence of the Martian lakes themselves is also still debated. After the 2018 discovery, researchers raised concerns such as the lack of an adequate heat source to turn the ice into water. And although the latest finding supports the 2018 observation and involves much more data, not everyone is yet convinced that the regions identified are liquid water.

 “If the bright material really is liquid water, I think it’s more likely to represent some sort of slush or sludge,” says Mike Sori, a planetary geophysicist at from Purdue University, in West Lafayette, Indiana.