No detection of SO2, H2S, or OCS in the atmosphere of Mars from the first two Martian years of observations from TGO/ACS

The detection of sulphur species in the Martian atmosphere would be a strong indicator volcanic outgassing from surface Mars. We wish to establish presence SO2, H2S, or OCS determine upper limits on their concentration absence detection. perform comprehensive analysis solar occultation data mid-infrared channel Atmospheric Chemistry Suite instrument, board ExoMars Trace Gas Orbiter, obtained during years 34 and 35. For most optimal sensitivity conditions, we 1-sigma SO2 at 20 ppbv, H2S 15 0.4 ppbv; last value is lower than any previous imposed literature. find no evidence these above 3-sigma confidence threshold. therefore infer that passive must below 2 ktons/day.