Ground-based mapping of SO₂ and HDO on Venus in the thermal infrared

Abstract : This paper describes the results of an observing campaign devoted to thestudy of SO2 and HDO (as a tracer of H2O) at the cloudtop of Venus usingthermal imaging with the TEXES imaging spectrometer at the InfraRedTelescope Facility (MaunaKea Observatory). The data, recorded since2012, have shown that SO2 and H2O have very different behaviors. SO2shows a patchy distribution over the Venus disk and strong short-termvariations (with a time scale of a few hours), and also strong long-termvariations (by a factor higher than 10) between 2012 and 2018. H2O incontrast, is uniform over the disk with moderate long-term variations(about a factor 2 between 2012 and 2012). The SO2 plumes are mostlyconcentrated around the equator and seem to show a depletion aroundnoon. There is a very good ageement between the TEXES results on SO2,obtained in the thermal infrared, and the UV results of Venus Expressand Akatsuki.