太陽系冰質小天體的協同研究

In this project, we investigate the exospheres of Europa and the comet 67P/C–G using with the radio data observed by ALMA (Atacama Large Millimeter/submillimeter Array) and by MIRO (Microwave Instrument for the Rosetta Orbiter). Understanding the chemical composition of the icy satellites such as Europa and their evolved exospheres, in analogy to the cometary coma, would reveal the secret of origin and distribution of water and other volatile organic molecules in the solar system. These two targets are so intriguing revealed with the remarkable discoveries made by the space missions. For example, a global subsurface ocean has been inferred to exist inside Europa from the diversity of surface geological features and the magnetic field measurements made by the Galileo spacecraft. In addition, the HST observations also suggested water vapors outgassing from Europa, similar to Enceladus. In addition, the Rosetta spacecraft arrived Comet 67P/ C-G in 2014 and orbited it for about two years. For the first time, the Rosetta spacecraft explored the cometary nucleus and its environment in such great detail. In this proposed work, we have analyzed a part of the ALMA data of Europa’ exosphere. The preliminary results showed the existence of some molecular gas. However, the gas source mechanism is still not clarified. It could be produced from sputtering of the Jupiter’s magnetospheric plasma impacts, and/or from the outgassing activity associated with its subsurface ocean. Further analysis is needed to help solve this question. For example, other detected molecular species such as NaCl, KCl and H2O in Europa’s exosphere could support the plume activity associated with its subsurface ocean. In the other hand, the nucleus and coma composition of the comet 67P has been investigated with the Rosetta MIRO data. It’s found some active regions on the surface of the cometary nuclei, and an inhomogeneous body is suggested from our analysis of the CH3OH and H2O in the MIRO data. Next step, we will study the dust-gas interaction by comparing with the jets and outburst events observed by OSIRIS. A 3D non-LTE radiative transfer model will be used to retrieve the scientific information of gas column density, temperature and expansion velocity from the radio line profiles observed by MIRO and ALMA.