The dust and gas analysis at 67P/Churyumov-Gerasimenko sheds light on cometary activity

The analisys of gas and dust in the coma of comets becomes crucial to understand the cometary activiy and represents an important reference for the new ESA mission as Comet Interceptor and for the small bodies showing ‘’cometary activity’’. Cometary activity consists in the ejection from cometary nuclei of dust and gas molecules induced by ice sublimation. Cometary activity offers a valuable window into the composition of comet nuclei with his forceful ejection of dust and gas that reveals interior components of the comet. During the period between July and November 2015, the Rosetta spacecraft had monitored the inner coma of comet 67P/CG. The Visible InfraRed the Thermal Imaging Spectrometer (VIRTIS) and the ALICE ultraviolet spectrograph, onboard Rosetta observed and detected a series of outbursts and jets. H2O, CO2, CO, and O2 were all indirectly observed by ALICE within outbursts via emission from the daughter products H, C, and O, identified in the spectra as the first three members of the H I Lyman series, OI multiplets at 1152, 1304, and 1356 Å, and weak multiplets of C I at 1561 and 1657 Å . VIRTIS detected and characterized the dust properties of the jets and outburst in terms of radial profile, light curve, color, and dust mass loss in the VIS and IR wavelength range. The aim of this work is to take advantage of the capabilities of two instruments to analyze the dust and gas coma during these cometary features. The outburst observations show that mixed gas and dust outbursts can have different spectral signatures representative of their initiating mechanisms, with outburst showing indicators of a cliff collapse origin or showing fresh volatiles being exposed via a deepening fracture. Preliminary analisys shows the cometary activity observed after some outburst events has a moderate CO2/H2O ratio, evidence that O2 may have initiated the outburst and exposed new volatile-rich material.  This analysis opens up the possibility of remote spectral classification of cometary activities with future work.