Phoenix studies soil on Mars
The unmanned Phoenix rover has generated results that convince even skeptics like myself that Mars does have soil. Mildly alkaline (pH range from 8-9) and containing both water vapor and carbon dioxide gas, the material shown on the scoop in the above photograph should certainly be "capable of supporting plants out of doors."
There is even a snazzy video to please the masses. Now all we need to find out is whether the soil has in fact supported plants, microbes, or other critters at some point in the past.