On October 19th 2014, Mars experienced a close encounter with Comet C/2013 A1 (Siding Spring), at a distance of only 141,000 km, or one third the Earth Moon distance. The gaseous coma washed over Mars and Mars passed directly through the cometary debris stream. As a close encounter of this type is predicted only once in 100,000 years, this is likely the only opportunity for measurements associated with planetary/cometary encounters. This unique event enables the scientific community to investigate the response of the Martian atmosphere, as this may have implications for overall atmospheric evolution. In addition, the encounter was complicated by the impact of an Interplanetary Coronal Mass Ejection (ICME) just prior to closest approach.

This session welcomes papers on the many different aspects of the interaction between the coma and the Mars system, such as delivery of pickup ions, impact of high energetic particles, induced magnetosphere, escape rates, dust deposition, ion-neutral chemistry, atmospheric dynamic effects, formation of metallic layers and meteoric smoke particles, ice cloud nucleation, etc. Furthermore, we welcome papers on the space weather effects during the encounter, including numerical simulations of the Martian system.