Energetic particle showers over Mars from comet Siding-Spring

International audienceOn 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 [1]. 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. Additionally, the encounter was masked by the transit of a powerful Coronal Mass Ejection (CME) 44 hours before [2]. Thus, the comet flyby took place when the Martian plasma system was still recovering from the CME impact, whilst the solar wind passing Mars remained significantly disturbed. In this study, we investigate the interaction of the comet with the solar wind, and their effects on the shock-accelerated energetic particles that precipitate into the Mars’ atmosphere. The study is based on data from MAVEN, Mars Odyssey, MSL and Mars Express missions