Today's Images of Mars are two topographic maps of Mars from the Mars Orbiter Laser Altimeter (MOLA), which show the enormous variance in altitudes on The Red Planet. As you can see, much of the Northern hemisphere is much lower than the Southern hemisphere. The Northern hemisphere on Mars is 1-3km lower than the Southern hemisphere. The crust in the northern hemisphere averages 32 km thick, but the crust in the southern hemisphere averages 58 km thick.
There are numerous theories to explain this highland-lowland dichotomy. In a previous post I detailed these theories, but I will reproduce them below:
