The good people working on the High Resolution Imaging Science Experiment (HiRISE) at the University of Arizona have provided several digital terrain model (DTM) files of the expected MSL landing site at Gale Crater. These files give, at a resolution of one meter per pixel, the elevation of the Mars surface shown in the corresponding visual images taken by the HiRISE camera.
Neighboring pixels can be compared in elevation to get an estimate of the slope of the terrain at each point, in degrees, where 0° is horizontal and 90° is vertical. Here’s the result of such a process applied to a mosaic of all the publicly available DTM models for the landing site:
MSL will in all probability land in the ellipse drawn on the map above. Slope in the map is color-coded as follows:
It’s important to know the slope because the practical limit for the Curiosity rover on its drives is 25°. Thus it can be seen that areas of the map colored red, orange or yellow are generally traversable by Curiosity (at least on the basis of slope), while the other colors green, blue, indigo and violet are increasingly off-limits.
If the full-res image is larger than you want to deal with, here’s a downsampled version at 4 mpp: