Mercury’s Complex Exosphere: What Have We Learned From MESSENGER?
When
Where
Senior Research Scientist
Johns Hopkins University - APL
Mercury’s exosphere – as the planet’s highly tenuous atmosphere is known – was discovered during the Mariner 10 flybys of 1974-1975. Ground-based observations from the mid-eighties until the present have added to our knowledge of both the exospheric composition and structure. However, observations of Mercury are difficult from the ground and some wavelength regions are inaccessible owing to the terrestrial atmosphere. It was not until the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) mission that we got our first up-close look at the inner workings of Mercury’s exosphere. During MESSENGER’s four Earth years in orbit (more than sixteen Mercury years), regular observations of the exosphere were conducted with the Ultraviolet and Visible Spectrometer (UVVS) instrument. These observations have detected new constituents in the exosphere and revealed a complex spatial structure and temporal behavior that have forced a revision of many of the pre-MESSENGER concepts. During this talk, I will highlight the results from the MESSENGER mission, summarizing what we thought we knew going in, how that thinking has changed, and where we go from here.