The hunt for evidence of past or present life on Mars has gotten a number of boosts in recent decades, including the discovery of what might be organic molecules in rock samples, but the biggest question on the minds of those who imagine the planet might have supported life is that of water. Water is crucial to life as far as we understand it, but it’s hard to come by on Mars. Now, researchers claim that they’ve discovered what might very well be a persistent Martian “lake” sitting just below the surface.

A new paper published in Science explains how the subsurface lake was discovered. It’s situated near the planet’s South Pole, where thick layers of ice have been observed in the past. If there is indeed a persistent body of water there, it could have huge implications for future Mars missions.

The supposed lake was discovered using radar technology on the Mars Express spacecraft which relayed data between mid-2012 and late 2015. That data revealed what appears to be evidence of liquid water sitting trapped beneath the ice on the planet’s pole.

We’ve known for some time that Mars still has at least a little bit of water left, and that it flows from time to time as ice melts and reforms throughout the course of the planet’s seasons. However, stable bodies of water have been elusive, and this may be the first concrete data that shows a body of water that remains in place for the entire Martian year.

“It’s probably not a very large lake,” Professor Roberto Orosei, lead author on the study, explains. “This really qualifies this as a body of water. A lake, not some kind of meltwater filling some space between rock and ice, as happens in certain glaciers on Earth.”

That’s incredible news for scientists hoping to discover evidence of Martian life, even in the smallest forms, but actually searching the area will prove to be a challenge. There’s no manmade craft or rover near Mars that can explore the area, and at present there’s no plans to actually go to the site where the lake may be hiding. That could change in the future, but for now we’ll all just have to wonder.