1.) The recent GRS measurements from Mars Odyssey showing significant amounts of water/ice *within centimeters* subsurface at some sites near the equator, including Gusev, is majorly important. There had been a few studies suggesting there might be liquid water at some sites on Mars but these would be close to the equator and would therefore be desiccated. These new GRS results show there is indeed water at such sites close to the equator.
You don't cite those previous studies when it was believed there was no water content near the equator, and then ignore them when it is found out there is.
2.) It has been known since Viking that temperatures near the equator can exceed 20 C.
3.) By comparison to the Pathfinder and Viking 1 lander sites at similar elevations to Gusev, the pressure at Gusev should always be above the triple point for pressure 6.1 millibars, as it was at those two sites.
4.) Several experimental studies showing liquid water could exist under simulated Martian conditions. The idea that liquid water would immediately vaporize in the Martian environment was based on theoretical studies. The experiments do not support that idea.

Bob Clark