Particle Release Processes and Radiation Environment On Mercury`s Surface In View of Esa`s Bepicolombo Mission
Abstract
A detailed study of Mercury`s exosphere-surface interaction by the "Mercury Appara- tus for Ions and Atoms" (MAIA) on board ESA`s Mercury Planetary Orbiter (MPO) will give the scientific community the first chance to study the efficiency of various gas release processes from a planetary surface. Particle ejection processes such as photon stimulated desorption, electron stimulated desorption, thermal desorption and particle sputtering of the surface constituents depend mainly on the mineralogical and geochemical properties of Mercury`s surface, micrometeorite impacts, and incoming solar UV irradiation, as well as cosmic ray and solar wind particle exposure. Our study investigates energy and particle ejection-angle distributions of H, He, O, Na and K atoms as a function of altitude in Mercury`s exosphere. The particles in our model are released from Monte-Carlo generated velocity distributions which resemble very well the velocity distributions for thermal desorption and particles which originate through plasma sputtering, as well as particles released from micrometeorite vapor- ization. To gain an idea of how efficient photon-stimulated surface release processes are, we also studied the total surface UV irradiation over Mercury`s dayside area dur- ing one Mercury year. Our study deduces that the MAIA instrument will detect all exospheric constituents between MPO`s periherm and apoherm of 400 km and 1500 km, but heavy particles like O, Na and K will only reach the spacecraft altitude if they originate through energetic source processes such as particle surface sputtering and micrometeorite vaporization.
- Publication:
-
EGS General Assembly Conference Abstracts
- Pub Date:
- 2002
- Bibcode:
- 2002EGSGA..27.1908L