A comparison of the exospheres of mercury and the moon

Ground-based optical studies of the similarities and dissimilarities of the sodium emissions of Mercury and the Moon have provided a lot of important information on the basic structures and dynamics of these two surface-bound exospheric systems. There are a number of key issues to be clarified. These include the relative importance of ion sputtering in producing sodium atoms (and hence other gas species) comparison to meteoroid impact and photodesoption effect, and the potential importance of magnetic anomalies (if exist) in modifying the space weathering effect of Mercury's surface. The new observations from the MESSENGER spacecraft at Mercury and the several lunar orbiters including Kaguya of Japan, Chang'e-1 of China and Chandrayaan-1 of India are expected to bring us answers and, certainly, far more questions to these two atmospheres of unique importance in comparative planetology.