Experiments conducted on a dry and a water-saturated rock under Martian and Earth atmospheric pressures revealed two different wear behaviors in diamond-impregnated drill bits. When the rock was saturated, drilling under Martian pressure caused the water in contact with the rotating bit to vaporize. Since the volumetric expansion of the liquid water or ice as it turned into a vapor was 170,000, the continuous flow of water vapor cleared the cuttings out of the hole. Thus the bit matrix was always exposed to abrasive wear by the rock cuttings and was continually wearing down and exposing new diamonds to the rock. When the rock was dry, an accumulation of rock cuttings protected the matrix from abrasive wear. Since fresh diamonds were not exposed in a timely manner, the rate of penetration dropped. Both rock conditions, namely, dry or water saturated, may exist on Mars. This adds to the complexity of the drill bit design as, ideally, a bit should penetrate the rock irrespective of whether it is dry or water saturated. The fail-safe bit would have a very soft matrix to always produce some rock penetration at the expense of potential excessive bit wear and shallower than anticipated hole depth.