Upon observing an area that’s around 75,000 square kilometers in size, they found locations that reflected those signals back in a way that indicates the presence of water trapped underneath a kilometer of ice. The main lake, the one discovered back in 2018, measures 30 kilometers or 19 miles across, while each of the three smaller lakes surrounding it are a few kilometers across.

While the scientists’ findings are promising, some experts still believe we won’t find lakes on the red planet at all. Jack Holt, a planetary scientist part of NASA’s Mars Reconnaissance Orbiter program, doesn’t believe there’s enough heat flow under the surface of the planet for water to remain liquid. And even if we do find liquid water under Martian ice, that won’t automatically mean we’ll also find life. See, the lakes have to be very salty to remain liquid, but their salt content must not exceed five times that of seawater to be able to support life. As John Priscu, an environmental scientist at Montana State University, told Nature:

“There’s not much active life in… briny pools in Antarctica. They’re just pickled. And that might be the case [on Mars].”