Italian scientists searching for evidence of water on Mars—even signs that it was there billions of years ago—believe they've found a lake filled with the liquid just a mile beneath the Red Planet's southern polar ice cap. Though outside experts have yet to confirm the finding, the body is thought to be 12 miles wide and potentially saturated with salts like sodium, magnesium, and calcium that would lower the water's melting point and allow it to stay in liquid form despite the cold temperatures, Popular Mechanics reports via the study published in Science. Per CNN, it's based on 29 observations of Mars’ Planum Australe region during a 3.5-year radar survey, completed in 2015 by the European Space Agency's Mars Express spacecraft.
A mile below the ice-covered surface, variations in radar signals revealed what appeared to be a lake similar to those found beneath Earth's ice sheets. The AP notes the researchers weren't able to establish the depth of the lake, which it reports prevents them from specifying "whether it's an underground pool, an aquifer-like body, or just a layer of sludge." Still, the scientists say they "interpret this feature as a stable body of liquid water on Mars," and they're already imagining a connecting system of waterways. There's a major caveat, though: Subsequent radar scans, including by the Mars Reconnaissance Orbiter, have failed to find the same signs. They remained elusive "even when we recently summed together [thousands] of observations to create CATSCAN-like 3D views of both polar caps," a scientist tells CNN. That said, the research team claims it, too, had difficulty establishing the lake's presence until it fixed a data processing issue. (Read more Mars stories.)