http://www.sciencemag.org/news/2018/07/liquid-water-spied-deep-below-polar-ice-cap-mars

Liquid water lies unseen under ice (white) at Mars’s south pole in an image from Mars Express.

Far beneath the deeply frozen ice cap at Mars’s south pole lies a lake of liquid water—the first to be found on the Red Planet. Detected from orbit using ice-penetrating radar, the lake is probably frigid and full of salts—an unlikely habitat for life. But the discovery, reported online today in Science, is sure to intensify the hunt for other buried layers of water that might be more hospitable. “It’s a very exciting result: the first indication of a briny aquifer on Mars,” says geophysicist David Stillman of Southwest Research Institute in Boulder, Colorado, who was not a part of the study.