Why doesnt NASA just land their Martian probe on one of the ICE ?CAPS and save a little money?

Question

Why doesnt NASA just land their Martian probe on one of the ICE ?CAPS and save a little money?

Answer 1

The Martian ice caps are subjected to a seasonal layer of several m think of frozen carbon dioxide that would totally disable the probe. Landing on ice is not also very recommended as the heat from thrusters will melt the surface and make the probe sink. Further, that far north (or south) means little to no light for the solar panels; and to top it off, being on top of the ice caps themselves means that the probe would be sitting on top a a layer of ice than can be a couple of km thick, that is pretty far from the soil NASA wish to study.

There is water on Mars; what Phoenix is after is finding present or past traces of *liquid*  water.