No Detection Of SO2, H2S, or OCS In The Atmosphere Of Mars From The First Two Martian Years Of Observations From TGO/ACS


Spatial and temporal distribution of all the ACS MIR observations covered in this analysis. Squares represent observations made by ACS using grating position 9 (sensitive to SO2), diamonds using grating position 5 (H2S), and triangles using grating position 11 (OCS). The colour of each symbol represents the time, in units of solar longitude (Ls) over Martian years (MY) 34 and 35, at which the observation was obtained. The relative concentration of observations made closer to the poles is due to the TGO orbital geometry. Latitude values are planetocentric. The background image of Mars is based on topography data from the Mars Orbiter Laser Altimeter (MOLA) instrument on board Mars Global Surveyor (Smith et al. 2001).

The detection of sulphur species in the Martian atmosphere would be a strong indicator of volcanic outgassing from the surface of Mars.

We wish to establish the presence of SO2, H2S, or OCS in the Martian atmosphere or determine upper limits on their concentration in the absence of a detection. We perform a comprehensive analysis of solar occultation data from the mid-infrared channel of the Atmospheric Chemistry Suite instrument, on board the ExoMars Trace Gas Orbiter, obtained during Martian years 34 and 35.

For the most optimal sensitivity conditions, we determine 1-sigma upper limits of SO2 at 20 ppbv, H2S at 15 ppbv, and OCS at 0.4 ppbv; the last value is lower than any previous upper limits imposed on OCS in the literature. We find no evidence of any of these species above a 3-sigma confidence threshold. We therefore infer that passive volcanic outgassing of SO2 must be below 2 ktons/day.

Ashwin S. Braude, F. Montmessin, K. S. Olsen, A. Trokhimovskiy, O. I. Korablev, F. Lefèvre, A. A. Fedorova, J. Alday, L. Baggio, A. Irbah, G. Lacombe, F. Forget, E. Millour, C. F. Wilson, A. Patrakeev, A. Shakun

Comments: 13 pages, 12 figures, received for production in A&A on the 19th of November 2021
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2111.10222 [astro-ph.EP] (or arXiv:2111.10222v1 [astro-ph.EP] for this version)
Submission history
From: Ashwin Braude
[v1] Fri, 19 Nov 2021 13:56:44 UTC (7,815 KB)
https://arxiv.org/abs/2111.10222
Astrobiology, Astrochemistry,

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