Herschel/HIFI observations of Mars: first detection of O_2 at submillimetre wavelengths and upper limits on HCl and H_2O_2

Abstract

We report on an initial analysis of Herschel/HIFI observations of hydrogen chloride (HCl), hydrogen peroxide (H_2O_2), and molecular oxygen (O_2) in the Martian atmosphere performed on 13 and 16 April 2010 (L_s ~ 77°). We derived a constant volume mixing ratio of 1400 +/- 120 ppm for O_2 and determined upper limits of 200 ppt for HCl and 2 ppb for H_2O_2. Radiative transfer model calculations indicate that the vertical profile of O_2 may not be constant. Photochemical models determine the lowest values of H_2O_2 to be around L_s ~ 75° but overestimate the volume mixing ratio compared to our measurements.

Accepted for publication in Astronomy and Astrophysics (special issue on HIFI first results); minor changes to match published version

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• HIFI Observations of Water in the Atmosphere of Comet C/2008 Q3 (Garradd)
• Mesospheric vertical thermal structure and winds on Venus from HHSMT CO spectral-line observations
• Water production in comet 81P/Wild 2 as determined by Herschel/HIFI
• First results on Martian carbon monoxide from Herschel/HIFI observations

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