# # Program information file # PROGRAM_ID 2023B002 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 Hideo Sagawa PROGRAM_INV5 Thomas Widemann 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 Venus atmosphere atop and within the clouds. Since 2012, maps of SO2 and HDO have been repeatedly recorded at 7 and 19 microns. These data have shown that SO2 atop the clouds shows strong long-term variations. Between 2014 and 2019, they also show 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, possibly the result of vertical motions. Since 2021, the SO2 abundance has also significantly decreased [by a factor 3] with respect to its highest values. In addition, since 2012, data show that SO2 plumes appear and disappear at the cloud top with a lifetime of a few hours. In November 2021, a very strong plume activity has been observed, in spite of the low disk-integrated abundance of SO2. We also noticed variations in the vertical gradient of SO2 which is usually close to zero, but in some cases positive or negative. We propose to continue this campaign with the following objectives: [1] to study the relative evolution of the disk-integrated SO2 and H2O abundances; [2] to further constrain the intensity, lifetime and evolution of the SO2 plumes; [3] to investigate the evolution of the SO2 vertical gradient as a function of time. 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. We plan to coordinate with the Akatsuki team for simultaneous observations, for comparing the SO2 measurements from Akatsuki UVI and from TEXES. PROGRAM_ABSTRACT_END