太陽系冰質小天體的協同研究 - 第二階段

Europa is an icy satellite orbiting Jupiter which is suggested to have a global subsurface ocean 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 plume activity. In this proposed work, we have completed the ALMA (Atacama Large Millimeter/submillimeter Array) data analysis of Europa’s exosphere. The preliminary results showed the existence of some molecular gas such as H2O. The local density enhancement in the exosphere and its high ejection velocity suggest that the H2O gas could be likely the outgassing activity associated with its localized liquid water reservoir and/or its subsurface ocean. Further spectral data of other molecular species such as NaCl and KCl is under investigation, and it will help us understand Europa interior ocean chemistry and environment. In addition, we also study the comet 67P/C–G using with the MIRO (Microwave Instrument for the Rosetta Orbiter). The Rosetta spacecraft arrived at Comet 67P/ C-G in 2014 and orbited it for about two years. It was the first time that the Rosetta spacecraft explored the cometary nucleus and its environment in such great detail (i.e., at a distance < 400 km). We investigate the nucleus and coma composition of the comet 67P with the MIRO spectral profiles. The active regions on the surface of the cometary nucleus are identified, and it shows a higher abundance of CH3OH ice in the southern part of this icy body indicating an inhomogeneous nucleus. The dust-gas interaction is studied by comparing the MIRO gas data with the jets and outburst events observed by OSIRIS. Some simultaneous events of outgassing activity and dust jets are identified. Our work aims to improve understanding the chemical composition of the icy satellites such as Europa and their evolved exospheres, and the cometary coma. It will help reveal the secret of origin and distribution of water and other volatile organic molecules in the solar system.