The Phoenix Lander has tested a sample and confirmed that water is on Mars:
“We have water,” said William Boynton of the University of Arizona, lead scientist for the Thermal and Evolved-Gas Analyzer, or TEGA. “We’ve seen evidence for this water ice before in observations by the Mars Odyssey orbiter and in disappearing chunks observed by Phoenix last month, but this is the first time Martian water has been touched and tasted.”
Blendor 
It’s good that the question has finally been answered. However, it’s not all that simple. They’ve also found an oxidizing substance that they say is “detrimental” to us. We’ve got a long way to go before we can actually see a benefit in the red planet.