Mars has at least one huge subglacial lake of liquid water hiding underneath its surface, new findings from a team of Italian researchers confirm. It’s over 12 miles wide and is the first of its kind to be discovered on Mars, which had previously been thought to only contain ice. The discovery means we could be one step closer to finding evidence of extraterrestrial life on the red planet.

The discovery was made using the Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS), a high powered radar tool attached to and developed specifically for the Mars Express spacecraft, which has been orbiting Mars since 2003 as part of the European Space Agency’s mission to map Mars. MARSIS sends out radar pulses, which penetrate the icy Martian terrain before reflecting back onto the spacecraft. MARSIS then measures these reflected waves to figure out what it’s looking at. The European Space Agency first deployed the technology involved 13 years ago, scouring the Martian terrain proved invaluable for Professor Roberto Orosei of Italy’s National Institute of Astrophysics and his team.

Orosei and co. used MARSIS to measure a section of Mars’ canyon-filled southern ice cap called Planum Australe, which had been returning abnormal radar readings for a section of land in that area, between May 2012 and December 2015. Further investigation revealed a roughly 12 mile wide area located around one mile below the planet’s icy surface which produced a radio profile similar to that of one of Earth’s subglacial lakes.

“The limited raw-data coverage of the SPLD (a few percent of the area of Planum Australe) and the large size required for a meltwater patch to be detectable by MARSIS (several kilometers in diameter and several tens of centimeters in thickness) limit the possibility of identifying small bodies of liquid water or the existence of any hydraulic connection between them,” wrote Orosei in the paper “Radar evidence of subglacial liquid water on Mars,” which was published Wednesday in Science Magazine. “Because of this, there is no reason to conclude that the presence of subsurface water on Mars is limited to a single location.”