In their pursuit of finding life beyond Earth, scientists and researchers tend to look for water on other planets. One of their target areas over the years has been the Martian south pole, where novel discoveries have revealed that beneath a sheet of ice, there are several ponds surrounding a huge lake.

“Here we have not just an occasional body of water, but a system,” says Elena Pettinelli of Italy’s Roma Tre University, a co-author of a study describing the observations today in Nature Astronomy.

This follows scientists’ 2018 discovery, where the found a massive subglacial lake presumed to be a body of saltwater some 12 meters across. The same team of researchers has now probed the same area, suggesting that there may be several more bodies of water, smaller than the one they found in 2018, in the same region. Scientists believe that these lakes and ponds are actually the remains of an ancient ocean.

“The system was probably existing a long time ago, when the planet was very different, and this is maybe the remnant of that,” Pettinelli says.

However, not all scientists agree that the bodies of liquid found are actually water. They argue that the temperatures in the region in question rarely rise above minus 150°F. Therefore it is impossible for water to exist in these subzero temperatures. The opponents believe that the liquid in the region is, at best, a soggy puddle of sludge.

“Patchy sludge at best, maybe?” the University of Arizona’s Jack Holt, who studies Mars using similar techniques, writes in an email. “I’m not really sure what to make of it.”

Search for water in the southern part of Mars began in 2010 when Pettinelli and her colleagues recorded radar observations of a bright, reflective region area beneath glaciers in a region now called South Pole Layered Deposits. Pettinelli suggests that during her research, they weren’t particularly looking for water. But their ultimate discovery had stunned them too.

From 2012 to 2015, research had originally indicated that a large, salty lake might be buried beneath a region called Ultimi Scopuli. But at that time, scientists weren’t confident if the lake was an actual source of water or just saturated sediment. But since then, more than 105 additional observations have been recorded, which suggests that the discovery was indeed a reservoir of water.

The presence and abundance of water on Mars has been conventionally viewed with skepticism. It is believed that Mars used to be much more hydrous than it is now. But where the water has disappeared is still up for debate. The presence of ancient water bodies on Mars has been manifested by various topographical features including carved river beds, fanning deltas, and ancient shorelines. Now, scientists believe that the water has been locked into ice caps at the planet’s poles. These caps shrink and expand annually.

These ice caps and glaciers give bright reflections. While scientists do believe that this may be due to the water inside them, they cannot, as of yet, say for sure.

It is no surprise that the ice doesn’t melt easily on the Martian poles, where temperatures tend to average around minus 270°F. Although the temperatures below the surface are relatively warmer, they are nowhere near the figures needed for water to thrive.

In 2019, a team of scientists developed a new theory about the presence of water on Mars. They suggested that in wake of recent magnetic activity, a magma chamber may have opened up, heating the frigid ice into a more liquified state. Otherwise, in the absence of an underground heat source, it is hard prove that the discovery was indeed water.