Atmospheric Impacts of a Close Cometary Encounter

Stimulated by the close fly-by of Comet Siding Spring past Mars in 2014, this study explores the impact of a cometary fly-by on the chemistry and dynamics of the terrestrial atmosphere. Simulations were carried out using the Whole Atmosphere Community Climate Model (WACCM) for the example of Comet Halley having a closest approach of 100,000 km. A chemical ablation model (CABMOD) [1] was used to determine the injection of several meteoric species (Fe, Si, Mg, Na, S and H₂O) into the lower thermosphere, from the 401,000 tonnes of cometary dust over a period of 1 hour. Key effects of this additional input on the chemistry of the upper atmosphere and metal layers have been explored in the simulations; ionospheric perturbations and effects on mesospheric and stratospheric ozone chemistry have been assessed. Furthermore, dynamical perturbations resulting from a dramatic temperature increase in the MLT region have been modelled.

References:

[1] Carrillo-Sánchez, J. D., D. Nesvorný,P. Pokorný, D. Janches, and J. M. C. Plane (2016), Sources of cosmic dust in the Earth's atmosphere, Geophys. Res. Lett., 43, 11979-11986