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# Program information file
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PROGRAM_ID           2024B017
PROGRAM_TITLE        Ground-based thermal mapping of Venus with TEXES: HDO & SO2 monitoring
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 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 7.4 microns, located in our model 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 since 2021, possibly the result of vertical motions. Since 2023, the SO2 abundance has shown strong variations [by a factor > 4] on a time scale of a few months only. In addition, the SO2 gradient between 57 km [19 microns] and 62 km [7.4 microns] shows strong variations, being either positive or negative. In October 2023, SO2 has been detected for the first time at 8.6 microns [67 km], which indicates a depletion by a factor 15 between 62 and 67 km; however, this signature was undetected in July 2023, implying a depletion factor  > 40. 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 improve 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 evolution of the SO2 plumes [given their lifetimes, which are typically a few hours], [4] to further constrain the vertical distribution of SO2 above and below the cloud top; [5] to compare the IR SO2 maps with the UV maps of Akatsuki, by performing simultaneous observations.  
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PROGRAM_ABSTRACT_END