The mole can deflect around small obstacles and move along the face of angled rocks. If it arrives at a large, flat surface directly below it, that will be as far as it goes. The landing will be livestreamed from mission control here at JPL on http://nasa.gov/live on Nov. 26!
It's a little more straightforward than that (excuse the pun). The percussive movement of the mole would slide it along the angled surface, and once it has cleared that surface, it would tend to straighten out again.
