The Mars Express [esa.int] mission orbiting Mars (not the Beagle II part that crash-landed) has discovered liquid water in the south polar region of Mars [esa.int].
The orbiter has been patiently circling Mars since 2003, using its ground-penetrating radar to map the surface up to a certain depth.
And now the ESA scientists found a bright spot that they think is an underground lake.
Main source: Mars Express detects liquid water hidden under planet's south pole [esa.int].
Other links:
BBC: Liquid water 'lake' revealed on Mars [bbc.com]
Science: Liquid water spied deep below polar ice cap on Mars [sciencemag.org]