Annual Appearance of Hydrogen Chloride on Mars and a Striking Similarity With the Water Vapor Vertical Distribution Observed by TGO/NOMAD

S. Aoki (1, 2, 3) , F. Daerden (2) , S. Viscardy (2) , I. R. Thomas (2) , Justin T. Erwin (2) , S. Robert (4, 2) , L. Trompet (2) , L. Neary (2) , G. L. Villanueva (5) , G. Liuzzi (6, 5) , M. M. J. Crismani (5, 7) , R. T. Clancy (8) , J. Whiteway (9) , F. Schmidt (10) , M. A. Lopez‐valverde (11) , B. Ristic (2) , M. R. Patel (12, 13) , G. Bellucci (14) , J.-J. Lopez‐moreno (11) , Kevin S. Olsen (15) , Franck Lefèvre (16) , Franck Montmessin (16) , A. Trokhimovskiy (17) , A. A. Fedorova (17) , Oleg Korablev (17) , A. C. Vandaele (2)

1 ISAS - Institute of Space and Astronautical Science
2 BIRA-IASB - Belgian Institute for Space Aeronomy / Institut d'Aéronomie Spatiale de Belgique
3 LPAP - Laboratoire de Physique Atmosphérique et Planétaire
4 IMCN - Institut de la matière condensée et des nanosciences / Institute of Condensed Matter and Nanosciences
5 GSFC - NASA Goddard Space Flight Center
6 Department of Physics [Washington]
7 CSUSB - California State University [San Bernardino]
8 SSI - Space Science Institute [Boulder]
9 CRESS - Centre for Research in Earth and Space Science [Toronto]
10 GEOPS - Géosciences Paris Saclay
11 IAA - Instituto de Astrofísica de Andalucía
12 School of Physical Sciences [Milton Keynes]
13 RAL Space - Space Science and Technology Department [Didcot]
14 IAPS - Istituto di Astrofisica e Planetologia Spaziali - INAF
15 Department of Physics [Oxford]
16 PLANETO - LATMOS
17 IKI - Space Research Institute of the Russian Academy of Sciences

Hydrogen chloride (HCl) was recently discovered in the atmosphere of Mars by two spectrometers onboard the ExoMars Trace Gas Orbiter. The reported detection made in Martian Year 34 was transient, present several months after the global dust storm during the southern summer season. Here, we present the full data set of vertically resolved HCl detections obtained by the NOMAD instrument, which covers also Martian year 35. We show that the particular increase of HCl abundances in the southern summer season is annually repeated, and that the formation of HCl is independent from a global dust storm event. We also find that the vertical distribution of HCl is strikingly similar to that of water vapor, which suggests that the uptake by water ice clouds plays an important role. The observed rapid decrease of HCl abundances at the end of the southern summer would require a strong sink independent of photochemical loss.

Domains: Sciences of the Universe [physics]

S. Aoki, F. Daerden, S. Viscardy, I. R. Thomas, Justin T. Erwin, et al.. Annual Appearance of Hydrogen Chloride on Mars and a Striking Similarity With the Water Vapor Vertical Distribution Observed by TGO/NOMAD. Geophysical Research Letters, 2021, 48 (11), pp.e2021GL092506. ⟨10.1029/2021GL092506⟩. ⟨insu-03251165⟩