Note: water on Mars... a while ago

The guardian has reported recent research which has shown Mars once held a large ocean. They've been looking at evidence of deltas and river channels, though it's also possible they were formed through volcanic activity. They theorise now that Mars's atmosphere, whatever it was like, maybe have boiled away as a result of cimate changes, taking the ocean with it. 

It was a hell of a long time ago, though, apparently 3.5 billion years... so maybe alittle too long to hope for say, evidence of life.

Artist's impression of Martian ocean shoreline, taken from
the Guardian article linked above.