NASA’s Mars Exploration rovers (MER) Spirit and Opportunity conducted the most successful exploration of a planetary surface in history. Rover mobility, critical to the MER’s exploration successes, presented few challenges with the exception of some occasions when the rovers became bogged in soils with wheel slips near 100%. These bogging events demonstrated that loss of rover mobility from high wheel slip events was a serious hazard to mission success and pointed to the need for a realistic model to simulate rover wheel mobility at high slip. The Coupi DEM was used to simulate MER rover wheel mobility for wheel slips from zero to 99%. Model development was guided by using the physical parameters of Mars soil simulant, MIT MER wheel mobility tests and DEM simulations of triaxial soil strength tests to match physical and DEM particle internal friction.