Abstract Details

Name: Sana Ahmed
Affiliation: Physical Research Laboratory
Conference ID: ASI2021_420
Title : Modelling the atmosphere of comets with different volatile compositions
Authors and Co-Authors : Sana Ahmed (Physical Research Laboratory, Ahmedabad; Indian Institute of Technology, Gandhinagar), Kinsuk Acharyya (Physical Research Laboratory, Ahmedabad)
Abstract Type : Oral
Abstract Category : Sun and the Solar System
Abstract : Comets are the most numerous objects of the Solar System, and are made up of frozen volatiles and refractory dust grains. They move in elliptical orbits about the sun, and solar heating causes the sublimation of the volatile ices, forming the cometary atmosphere or the coma. The volatile composition of the coma is generally diverse, but H2O is a primary constituent in most of the cases. This is followed by CO and CO2, whose abundance percentage with respect to H2O varies between 1% to 30%. Trace amounts of other species such as CH4, CH3OH, O2, and NH3 are also present. In some comets, the observed CO/H2O ratios are >> 1. One such comet that has a coma dominated by CO outgassing is C/2016 R2 (PanSTARRS). Solar UV radiation causes photodissociation of the sublimated parent volatile species in the coma, creating ions and radicals that drive the coma chemistry. The density in the inner region of the coma (~ 10000 km) is high enough to treat the coma gas as a fluid. We have constructed a fluid model, using the principles of conservation of mass, momentum and energy, in order to study the chemistry and dynamics of the coma. We have used the model to study comets having different volatile compositions. The model results show that when the dominant parent volatile changes from H2O to CO, there is significant alteration in the coma chemistry and dynamics. Varying the percentage of CO2, and other trace volatiles also changes the ion chemistry of the coma.