Venus' atmosphere: an overview before next exploration missions

International audienceDuring the last 15 years, our knowledge about the atmosphere of Venus has expanded greatly, mainly due to the contribution of two dedicated orbiters: Venus Express from ESA (2006-2014) and Akatsuki from JAXA (2015-present). Both missions included a comprehensive payload (imagers and/or spectrometers operating in the UV and/or IR range) which enabled them to measure key parameters about the atmosphere from the surface to the topmost layers. Among their discoveries are a much greater than anticipated spatial and temporal variability, in terms of minor species composition, cloud layers, dynamics and thermal structure. Most surprisingly, part of this variability was due to unsuspected coupling between the surface and the upper atmospheric layers at cloud top level. They also highlighted gaps in our knowledge, some of them long standing like the nature of the unknown UV absorber, that they could not solve. Undoubtedly, all these results contributed to the renewed interest for the planet Venus that was confirmed by the selection, in June 2021, of three space exploration missions targeting the planet in the 2030s. The science case of all these missions (DAVINCI and VERITAS from NASA, EnVision from ESA) include, to some extent, atmospheric characterization based on the aforementioned discoveries. This review talk will summarize our current knowledge about the atmosphere of Venus after Akatsuki and Venus Express, including some key outstanding questions. It will then proceed in a review of the planned atmospheric investigations from the above mentioned selected missions, as well as others from e.g. ISRO and Roscosmos