re: Temperatures everywhere on Mars are below the freezing point of water
The graph is recognized as showing subsurface ice by neutron emissions. This has nothing to do with the argument of water on the surface as this is underground. As Nick pointed out, the temperatures would probably keep this frozen. It doesn't necessarily mean blocks of ice, but some frozen moisture in the soil. The actual percentage of ice might be quite low.
The problem I was pointing out is if you have ice underground and olivine on top how did the ice get under the olivine without destroying it?