14:35 〜 14:55
[PPS05-04] Simulation of the Ca emission at Mercury and comparison with the observations by PHEBUS/BepiColombo during the first three flybys.
★Invited Papers
キーワード：Mercury, Exosphere, BepiColombo, Calcium
Due to the lack of a thick atmosphere, the surface of Mercury is regularly bombarded by micrometeoroids at a rate depending on the position of Mercury around the Sun. One consequence of these impacts is an alteration of its surface (space weathering) and the ejection of its material around Mercury forming a tenuous exosphere. Even if the detail on the origin of the exospheric atomic calcium, observed systematically by MESSENGER is not fully understood, it is mostly associated to such impacts. In order to interpret the MESSENGER observations, we have developed a time dependent 3D model of the Ca exosphere of Mercury and successfully reproduced the seasonal variations observed by MESSENGER at dawn during its orbital phase. In this presentation, we will present the observations performed by PHEBUS onboard BepiColombo during the first three flybys of Mercury. We will compare these observations with the simulated brightness using different horizontal distributions of the calcium ejection and with simulations from a new version of the model including a two steps process of exospheric Ca production.