Particle and Chemical Sputtering as a Source for the Exosphere of Mercury:
Modeling and Data Comparison
Alessandro Mura1, P. Wurz2, S. Orsini1, A. Milillo1, H. Lammer3
1
Institute of Interplanetary Space Physics, INAF-IFSI Rome
Physics Institute, University of Bern, Germany
3
Austrian Space Research Institute, Dept. of Extraterrestrial Physics, Graz, Austria
2
In this study we introduce a numerical model of the exosphere of Mercury, including several
different sources from a rotating surface. We first compare our model with either ground- and
space-based observations of the sodium exosphere and tail to evaluate the effectiveness of each
source process. We find that including a source process which effectiveness is proportional to the
precipitation of solar wind protons, such as chemical sputtering, is able to explain most of the
available observations in a quantitative way. To reproduce the dawn-dusk asymmetry as
observed from ground during the Schleicher et al. (2004) transit experiment, the rotation of
Mercury's surface has also to be included in the model. In addition to Na, we also simulate both
the Ca and Ca+ exosphere and tail taking into account the actual IMF and Mercury's position
during MESSENGER flybys, and we compare the results with observations.