| Auteur(s) supplémentaire(s) | A. Milillo1, A. Mura1, Andre’ N.2, C. Plainaki1,V. Mangano1, S. Massetti1, S. Orsini1, A. Aronica1, E. De Angelis1, R. Rispoli1, R. Sordini1, A. Kazakov1, D. Del Moro3 |
Abstract | The study of the micro-meteoroid environment is relevant to planetary science, space weathering of airless bodies, as Mercury, and their upper atmospheric chemistry. In this case, the meteoroids hit directly the surface without any interaction with the atmospheric particles, producing impact debris and contributing to shape its thin exosphere.
The study of the generation mechanisms, the compositions and the configuration of the Hermean exosphere will provide crucial insight in the planet status and evolution.
This work is focused on study and modelling of the Mercury’s exosphere formation through the process of Micro-Meteoroids Impact Vaporization (MMIV) from the planetary surface.
The MESSENGER/NASA mission visited Mercury in the period 2008-2015, providing measurements of unprecedented quality of Mercury’s exosphere, which permit the study of the seasonal variations of metals like Calcium. The Ca in Mercury’s exosphere exhibited very high energies, with a scale height consistent with a temperature > 20,000 K, seen mainly on the dawnside of the planet. The origin of this high-energy, asymmetric source is unknown.
The generating mechanism is believed to be a combination of different processes including the release of atomic and molecular surface particles and the photodissociation of exospheric molecules.
In this paper we work on models of Mercury’s impactors: we provide a detailed Ca-source extraction model simulating the expected 3-D Ca density distribution in Mercury’s exosphere due to the MIV mechanism. A prototype of the Virtual Activity (VA) SPIDER (Sun-Planet Interactions Digital Environment on Request) services is used as a Monte Carlo three-dimensional model of the Hermean exosphere to simulate the bombardment of Mercury’s surface by micrometeorites and to analyze particles ejected.
We study how the impact vapor varies with heliocentric distance and compare the results to the MESSENGER observations. The morphology of Mercury’s Ca and CaO exosphere is in good agreement with the observed Ca along the orbit, excluding specific events like comet stream crossing.
The results presented in this work will be useful for the exosphere observations planning and for the data interpretation in the frame of the ESA/JAXA BepiColombo mission, that will study Mercury orbiting around the planet from 2025. More specifically, the resulting molecular distributions will be compared to the measurements of the SERENA-STROFIO mass spectrometer that will be the only instrument able to identify the molecular components.
The Sun Planet Interactions Digital Environment on Request (SPIDER) Virtual Activity of the Europlanet H2024 Research Infrastucture is funded by the European Union's Horizon 2020 research and innovation programme under grant agreement No 871149.
|
