Martian Metallic Ions Deposited by Comet Siding Spring Defy Expectations

On October 19th 2014, comet C/2013 A1 (Siding Spring) had a close encounter with Mars and deposited cometary dust particles into the Martian atmosphere. Dust that impacted Mars was readily identifiable as the meteoric deposition of Mg, Fe, Na, etc. by the Imaging Ultraviolet Spectrograph (IUVS) and Neutral Gas and Ion Mass Spectrometer (NGIMS) on the NASA Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft. While Mg+ from comet Siding Spring and in a persistent layer was identified previously by IUVS, this is the first remote sensing report on the abundance, spatial distribution and temporal evolution of Mg, Fe, and Fe+. Subsequent evolution of the distributions of ions and neutrals indicate distinct physical mechanisms for distribution. We find vertical and latitudinal inhomogeneities that are inconsistent with expected dynamical transport mechanisms.