Martian Meteoric Mg+: Atmospheric Distribution and Variability From MAVEN/IUVS.

Since the discovery of atmospheric Mg+ on Mars in 2015 by the Mars Atmosphere and Volatile Evolution mission, there have been almost continuous observations of this meteoric ion layer in a variety of seasons, local times, and latitudes. Here, we present the most comprehensive set of observations of the persistent metal ion layer at Mars, constructing the first grand composite maps from pooled medians of subsamples of a metallic ion species. These maps demonstrate that Mg+ appears in almost all conditions when illuminated, with peak density values varying between 100 and 500 cm−3, dependent on season and local time. There exists significant latitudinal variation within a given season, indicating that Mg+ is not simply an inert tracer, but may instead be influenced by the meteoric input distribution and/or atmospheric dynamics and chemistry. Geographic maps of Mg+ density as a function of latitude and longitude indicate the influence of atmospheric tides, and there is no apparent correlation with remnant crustal magnetic fields. This work also presents counter‐intuitive results, such as a reduction of Mg+ ions in the northern hemisphere during Northern Winter in an apparent correlation with dust aerosols. Plain Language Summary: Metallic atoms in a planet's atmosphere are present when interplanetary dust particles burn up, releasing atomic species not typically found in the lower atmosphere. The discovery of a high altitude metallic layer on Mars in 2015 has led to continued monitoring in a variety of seasons across the entire planet. These results demonstrate that this magnesium ion (Mg+) layer appears throughout the year, with variations in peak abundances and layer heights, due to interactions with the background atmosphere. These variations track the dynamics of the middle atmosphere, providing insight into global climate patterns and may inform our understanding of seasonal deposition of interplanetary dust particles and their sources. This first‐order analysis supports future modeling efforts and provides model challenges to be understood, both of which can be explored in detail with time varying full planet climate modeling. Key Points: Eight Earth years of Mars Atmosphere and Volatile Evolution/Imaging Ultraviolet Spectrograph observations show that Mars' persistent meteoric metal ion layer is more dynamic than initially assumedMg+ layer peak altitude, abundance, and top and bottom side slopes vary significantly over the observed time periodThe relative absence of northern hemispheric Mg+ during southern summer is surprising and may be related to lower atmospheric dust loading [ABSTRACT FROM AUTHOR]