This observation shows a frozen terrain typical at these latitudes. The surface is mantled
by a deposit that is postulated to be largely a mix of dust and ice. However, many
of the higher hills have had this mantle removed and the older rocks are exposed. In
some parts of Mars there is good evidence for ice having !owed from higher to lower
ground, but there is no such evidence here. Perhaps the mantling deposit never
formed on the tops of these hills or it was preferentially removed from these places.