A Global Perspective on Martian Meteoric Mg+

Interplanetary dust particles, liberated from the surfaces of comets and asteroids, are ubiquitous in interplanetary space within the solar system. These particles travel at orbital velocities and ablate upon entry into planetary atmospheres, where they are the sole explanation for high altitude atmospheric metal layers. On Earth, such layers inform us of the dynamics of the upper atmosphere, and we use the abundance of relative species to investigate the origin of these particles from various potential sources (Jupiter family comets, asteroids, etc.). Since the discovery of atmospheric Mg+ at Mars in 2015, there have been almost continuous observations of this 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 average maps of metal ions species. Such maps can be compared to current and future modeling efforts, which attempt to track mesospheric transport, chemistry and interplanetary dust particle sources. This work confirms some previous model predictions and observations, such as the relatively long lifetime of Mg+, but also presents counter-intuitive results, such as a paucity of Mg+ ions in the northern hemisphere during Northern Winter in an apparent correlation with dust aerosols. Previous discrepancies between model predictions and metal ion observations led to the development of a novel nucleation scheme for mesospheric clouds, and we revisit these ideas on a global and seasonally varying scale. Overall, this represents the broadest investigation of meteoric metal ions, summarizes the first order behavior and outlines new model challenges for the future.