The Spatial and Temporal Distribution of Nighttime Ozone and Sulfur Dioxide in the Venus Mesosphere as Deduced from SPICAV UV Stellar Occultations

Abstract : The nighttime ozone and sulfur dioxide distributions were analyzed using the entire SPICAV‐UV/Venus Express stellar occultation dataset. After the discovery of an ozone layer at 100 km in the mesosphere reported by Montmessin et al. (2011), 132 other detections were made during the entire 8 years long observing period of the SPICAV UV instrument. In the rare detections the peak abundances of O3 accumulating in the mesosphere are observed with densities from 107 to 108 molecules⋅cm‐3 at 85‐110 km. The ozone layer is estimated to vary from 1 ppbv to 30 ppbv at 85‐95 km while at 95‐105 km the VMR is expected within an interval from 6 ppbv to 120 ppbv. Below 93 km, a puzzling decrease of mixing ratio is observed toward midnight at 30°N. Our work also provides an improved sequel to the analysis of the sulfur dioxide survey previously made in the upper mesosphere by Belyaev et al. (2017). On average, the SO2 content is found to remain constant throughout the vertical profile at a value of around 135±21 ppbv between 85 and 100 km. Rapid and large variations prevent to conclude firmly on any time or space pattern of SO2.