Rationale for BepiColombo Studies of Mercury’s Surfaceand Composition

BepiColombo has a larger and in many ways more capable suite of instrumentsrelevant for determination of the topographic, physical, chemical and mineralogical proper-ties of Mercury’s surface than the suite carried by NASA’s MESSENGER spacecraft. More-over, BepiColombo’s data rate is substantially higher. This equips it to confirm, elaborateupon, and go beyond many of MESSENGER’s remarkable achievements. Furthermore, thegeometry of BepiColombo’s orbital science campaign, beginning in 2026, will enable itto make uniformly resolved observations of both northern and southern hemispheres. Thiswill offer more detailed and complete imaging and topographic mapping, element mappingwith better sensitivity and improved spatial resolution, and totally new mineralogical map-ping.We discuss MESSENGER data in the context of preparing for BepiColombo, and de-scribe the contributions that we expect BepiColombo to make towards increased knowledgeand understanding of Mercury’s surface and its composition. Much current work, includinganalysis of analogue materials, is directed towards better preparing ourselves to understandwhat BepiColombo might reveal. Some of MESSENGER’s more remarkable observationswere obtained under unique or extreme conditions. BepiColombo should be able to confirmthe validity of these observations and reveal the extent to which they are representative ofthe planet as a whole. It will also make new observations to clarify geological processesgoverning and reflecting crustal origin and evolution.We anticipate that the insights gained into Mercury’s geological history and its currentspace weathering environment will enable us to better understand the relationships of surfacechemistry, morphologies and structures with the composition of crustal types, including thenature and mobility of volatile species. This will enable estimation of the composition of the mantle from which the crust was derived, and lead to tighter constraints on models forMercury’s origin including the nature and original heliocentric distance of the material fromwhich it formed.