EGU24-4022, updated on 08 Mar 2024
EGU General Assembly 2024
© Author(s) 2024. This work is distributed under
the Creative Commons Attribution 4.0 License.

Ground-based thermal mapping of Venus:  HDO and SO2 monitoring and upper limits of NH3, PH3 and HCN at the cloud top

Therese Encrenaz1, Thomas Greathouse2, Rohini Giles2, Thomas Widemann1, Bruno Bezard1, Franck Lefevre3, Maxence Lefevre4, Wencheng Shao5, Hideo Sagawa6, Emmanuel Marcq3, and Anicia Arredondo2
Therese Encrenaz et al.
  • 1Paris Observatory, LESIA, Meudon, France (
  • 2SWRI, San Antonio, TX, USA
  • 3LATMOS, IPSL, France
  • 4LMD, IPSL, France
  • 5DTU, Denmark
  • 6Kyoto University, Japan

As part of a long-term monitoring program, full disk thermal maps of HDO (near 7 microns) and SO2 (near 7 and 19 microns) have been obtained at the cloud top of Venus in 2023, using the TEXES(Texas Echelon Cross-Echelle Spectrograph)  imaging spectrometer at the Infrared Telescope Facility (IRTF) at Mauna Kea Observatory. Assuming a constant D/H isotopic ratio, the water abundance has been more or less constant since 2018, at about half its value in 2012-2016. In contrast, the SO2 abundance, which was very high in 2018-2019 and very low between July 2021 and March 2023, has increased by a factor of about 5 between February and July 2023 (close to its maximum level of 2018-2019), and has remained at its high level in September 2023. The origin of these long-term variations is still unclear. In addition, stringent upper limits of NH3 (at 927-931 cm-1), PH3 (at 1161-1164 cm-1) and HCN at 744-748 cm-1) at the cloud top have been obtained in July 2023. These results will be presented and discussed.

How to cite: Encrenaz, T., Greathouse, T., Giles, R., Widemann, T., Bezard, B., Lefevre, F., Lefevre, M., Shao, W., Sagawa, H., Marcq, E., and Arredondo, A.: Ground-based thermal mapping of Venus:  HDO and SO2 monitoring and upper limits of NH3, PH3 and HCN at the cloud top, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4022,, 2024.

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