Well that depends on if there really *is* a large anout of water there. Perhaps if there were, converters could be set up, and Mars could be Terraformed over a couple of hundred years...Or more...Ever read ‘Dune’?
Yes. But remember, it's science fiction.
What would be the point of terraforming a planet that never gets above -100c? even if something could be made to grow in that temperature? It would STILL be uninhabitable by man for many reasons, temperature, gravity, radiaton.
It's near impossible to live at the north pole on earth for any significant length of time, never mind mars with the barest of supplies and shelter.
Maybe in another 500 years or so we can go for a quick visit when we discover warp engines, Scotty. Or learn to open up worm holes, or space portals, or...