# # Program information file # PROGRAM_ID 2023A009 PROGRAM_TITLE Thermal mapping of SO2 and HDO at the cloud top of Venus PROGRAM_INV1 Therese Encrenaz PROGRAM_INV2 Thomas Greathouse PROGRAM_INV3 Rohini Giles PROGRAM_INV4 Thomas Widemann PROGRAM_INV5 Bruno Bezard PROGRAM_SCICAT major planets / satellites PROGRAM_ABSTRACT_BEG We propose to use TEXES to study spatial and temporal variations of SO2 and H2O [through its proxy HDO] in the atmosphere of Venus over and within the clouds. Since 2012, maps of SO2 and HDO have been repeatedly recorded at 7 and 19 microns to search for short-term and long-term temporal variations. These data have shown that the disk-integrated abundance of SO2 atop the clouds has significantly changed over this time period, by a factor up to 10. Between 2014 and 2019, they have also shown evidence for a long-term anticorrelation between SO2 and H2O, which has been analyzed through GCM photochemical models. Surprisingly, this anticorrelation is no more visible in 2021 and 2022, for reasons which are unclear; since. 2021, the SO2 abundance has also significantly decreased. [by a factor about 3] with respect to its highest values in 2018-2019. In addition, since 2012, the data have shown that SO2 plumes appear and disappear at the cloud top with a lifetime of a few hours. In November 2021, an unusual plume activity has been observed, the origin of which remains to be understood. We propose to continue this campaign with the following objectives: [1] to study the relative evolution of the disk-integrated SO2 and H2O abundances during 2023A; [2] to improve the statistics about the distribution of the SO2 plumes as a function of local time [which requires one measurement per day]; [3] to further constrain the lifetime and evolution of the SO2 plumes. In addition, [4] we plan to search for SO2 at 8.6 microns in a spectral range which probes a region located above the clouds, in order to better constrain the SO2 vertical profile within and above the clouds. PROGRAM_ABSTRACT_END