Meteoric Metal Layers in the Upper Atmosphere of Venus

About 30 tonnes of cosmic dust particles – mostly from Jupiter Family Comets - enters Venus’ atmosphere every (Earth) day, of which around 40% ablates. This causes the injection of various metals (Fe, Mg, Si and Na in particular) into the atmosphere between 105 and 125 km. By analogy with the Earth, these metals should provide important tracers of both chemistry and atmospheric dynamics. In order to guide future observations of these metals, both from terrestrial telescopes and spacecraft, we have developed detailed chemical networks for each of the elements. These networks are extensions of those used to model these metals in the terrestrial atmosphere, where the Fe, Mg and Na networks have been rigorously tested against observations of neutral and ionized metal atoms made with ground-based lidars, spaceborne spectrometers, and sub-orbital rockets. For Venus, we now include a detailed chlorine chemistry because of the very large concentration of HCl produced by volcanic emissions. Where reactions have not been studied in the laboratory, we have employed quantum chemistry calculations combined with master equation rate theory for reactions taking place on multi-well potential energy surfaces. These networks were then inserted into the global Venus Planetary Climate Model. The simulations reveal that the metal atoms occur in layers about 10 km wide which peak around 110 km, and the metal ion layers peak about 10 km higher. Below 105 km the metals form carbonates, which are then converted into chlorides by reaction with HCl emitted by surface volcanoes. In this presentation we will discuss the metal layer variability on the day- and night-side, and the feasibility of detecting Mg, Mg⁺ and Na by observing solar-pumped resonance fluorescence on the dayside, and Na chemiluminescence on the night-side.