IRTF Data Archive Program Information

# # Program information file # PROGRAM_ID 2021A008 PROGRAM_TITLE HDO and SO2 thermal mapping in the atmosphere of Venus PROGRAM_INV1 Therese Encrenaz PROGRAM_INV2 Thomas Greathouse PROGRAM_INV3 Rohini Giles PROGRAM_INV4 Emmanuel Marcq PROGRAM_INV5 Thomas Widemann PROGRAM_SCICAT solar system PROGRAM_ABSTRACT_BEG We are pursuing our ground-based campaign to monitor H2O and SO2 at the cloud top of Venus in the thermal infrared with TEXES [Encrenaz et al. [A&A 530, id.A37, 2012; 559, id.A65, 2013; 595, id.A74, 2016; 623, A70, 2019; 639, A69, 2020]. The main result is that SO2 and HDO behave very differently. SO2 shows strong local variations over the disk, and strong temporal variations [both short-term and long-term]. The lifetime of the SO2 plumes is a few hours at maximum. Between 2012 and 2019, the variations of the SO2 volume mixing ratio vary by a factor higher than 10 while, in contrast, the H2O volume mixing ratio [inferred from a HDO line] shows moderate variations with time and over the disk. Using new data obtained in 2019, we have shown that there is an anticorrelation between the two species [cc = - 0.8 between 2012 and 2019, and - 0.9 between 2014 and 2019]. This result has important implications in terms of photochemical models [Encrenaz et al. A&A, under revision, 2020]. We have also started a statistical analysis of the behavior of the SO2 plumes as a function of date, latitude, longitude and local time. The SO2 plumes appear to be localized at the equator, with two maxima around the terminators. There is a very good agreement between the TEXES data and the UV data of SPICAV/Venus Express and UVI/Akatsuki, which demonstrates that TEXES can be used as a proxy of the UV data to monitor SO2 during the night. The TEXES 2020 runs cancelled because of the pandemia. We ask for more time in 2021A to improve our statistics, enlarge our time coverage, and continue our comparison with Akatsuki data. PROGRAM_ABSTRACT_END