According to Space.com
it has been almost totally confirmed that water ice does in fact exist just below the surface of Mars. This is HUGE!
When the probe took photos of a ditch it had dug four days before, scientists noticed that about eight small crumbs of a bright material had disappeared. They concluded those crumbs had been water ice buried under a thin layer of dirt that vaporized when Phoenix exposed them to the air... If the crumbs had been salt, they wouldn't have disappeared, scientists said, and if the ice had been made of carbon dioxide, they wouldn't have vaporized.
Water is the most basic requirement for all life as we know it and finding it on Mars means two things. First, this could indicate that some form of life could exist beneath the surface of Mars. There could be bacteria or all kinds of weird single-celled organisms under there. Secondly, water ice on the planet opens the door for the possibility of colonization. We could, if the time and opportunity ever came, haul supplies and equipment to Mars but the existence of naturally occurring water would make the process incredibly easier and much more plausible. Amazing!