# # Program information file # PROGRAM_ID 2024A006 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 [at 7 um, located at z = 62 km] 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 until March 2023, the SO2 abundance has also significantly decreased [by a factor 3] with respect to its highest values [in 2018-19]. Surprisingly, SO2 has increased again in July 2023, back to its highest values; the reason for these long-term variations is unknown. In addition, we obtained in July 2023 an upper limit of SO2 in another band at 8.6 microns [z = 67 km], which implies that SO2 is depleted by a factor of 40 between 62 and 67 km altitude. 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 compare our results with the Akatsuki UVI images which measure the SO2 abundance in the UV at a slightly higher altitude level. PROGRAM_ABSTRACT_END