Researchers have found evidence of an existing body of liquid water on Mars. It is beleived to be a vast liquid water lake beneath it's southern pole and is about 20km across. In the previous searches, lake beds explored by NASA's Curiosity rover showed water was present on the surface of Mars in the past. But this is the first sign of a persistent body of water on the planet in the present day. The discovery was made using Marsis, a radar instrument on board the European Space Agency's Mars Express Orbiter.