According to new studies, remains of water once present on the surface of Mars could be concealed in a number of small lakes below the south pole of the Red Planet, and more may exist.
Researchers have speculated for decades that water lurks below Mars' polar ice caps, just as it does here on Earth. In 2018, scientists found evidence on the Red Planet for such a reservoir, signs of a lake about 12 miles long and concealed at the south pole of Mars within about a mile of ice.
The researchers said at the time that researching this underwater body of water could offer insights into the possibilities for life on Mars in the past and present. Scientists, however, had far more doubts than answers about this lake and its water's nature, composition, and longevity.
In the new study, researchers used the MARSIS radar sounder instrument aboard the Mars Express spacecraft of the European Space Agency to scan a 155-by-185 mile area circling the hypothesized underwater lake to learn more about this secret water. The scientists used techniques previously used to detect lakes under glaciers in Antarctica to study this radar data.
The researchers confirmed the liquid existence of the lake previously observed, reducing its measurements to about 12 by 18 miles in distance. As the radio waves from MARSIS do not reach salty water, they can not tell how far this lake spreads, study co-author Elena Pettinelli said.
In addition, on the order of 6 by 6 miles in scale, Pettinelli and her colleagues found three other lakes. Strips of dry shale, the scientists said, distinguish these smaller water patches from the main lake.
The researchers suggested that these lakes are particularly salty. Considering the exceptionally cold environments at the base of the glaciers at Mars' south pole, high brine content will hold their water warm, noted the scientists.
While Martian polar ice may melt a little due to warm noontime temperatures, scientists do not believe it is probable that these lakes were formed by such ongoing processes. Instead, Pettinelli added, scientists assume that this saltwater may be the remains of a greater body of water that is now being removed from the surface, and may be millions, or even billions, of years old.
The idea that geothermal activity may have melted polar ice to form underground lakes was suggested by scientists, but that explanation was feasible because only one such body of water was present. It might take a massive geothermal anomaly to form many lakes this way. "I don't think it is physically possible, given what we know," Pettinelli said.
A paper detailing the new findings has been published in the journal Nature Astronomy.
