Astronomers have discovered a large underground lake of liquid water lurking just below the surface of Mars. The find could end a more than century-long debate over whether or not the Red Planet still has liquid water.

The newfound lake stretches some 12 miles from end-to-end, and was discovered using a radar instrument called MARSIS on board the European Space Agency’s Mars Express spacecraft, which first reached Mars nearly 15 years ago. The results were published Wednesday in the journ