The Mars Reconnaissance Orbiter has detected large glaciers just under the surface of Mars.
This can be very interesting as water supply when (yes, I am optimistic) we send people to Mars – they do not have to bring large supplies of water. Could it be that – with care – the people going there can be self supporting with water supply ? Quite possible.
This is also a sign that Mars has had much more water than it has today. Maybe it even had an atmosphere dense enough to support life, more or less as we know it.