Researchers have found evidence of an existing body of liquid water on Mars. What they believe to be a lake sits under the planet's south polar ice cap, and is about 20km (12 miles) across.
Previous research found possible signs of intermittent liquid water flowing on the martian surface, but this is the first sign of a persistent body of water on the planet in the present day.
Lake beds like those explored by Nasa's Curiosity rover show water was present on the surface of Mars in the past. Take a look at what we know so far about this mysterious planet and the life that may be there.
(Source: BBC News YouTube channel)