After the Mars Polar Lander: Where to Next?

The recent loss of the Mars Polar Lander (MPL) mission represents a serious setback to Mars science and exploration. Targeted to land on the Martian south polar layered deposits at 76 degrees south latitude and 195 degrees west longitude, it would have been the first mission to study the geology, atmospheric environment, and volatiles at a high-latitude landing site. Since the conception of the MPL mission, a Mars exploration strategy has emerged which focuses on Climate, Resources and Life, with the behavior and history of water as the unifying theme. A successful MPL mission would have made significant contributions towards these goals, particularly in understanding the distribution and behavior of near-surface water, and the nature and climate history of the south polar layered deposits. Unfortunately, due to concerns regarding the design of the MPL spacecraft, the rarity of direct trajectories that enable high-latitude landings, and funding, an exact reflight of MPL is not feasible within the present planning horizon. However, there remains significant interest in recapturing the scientific goals of the MPL mission. The following is a discussion of scientific and strategic issues relevant to planning the next polar lander mission, and beyond.