Letter to the Editor

Herschel/HIFI observations of Mars: First detection of O₂ at submillimetre wavelengths and upper limits on HCl and H₂O₂ ^*

¹ Max-Planck-Institut für Sonnensystemforschung, 37191 Katlenburg-Lindau, Germany
² LESIA, Observatoire de Paris, 5 place Jules Janssen, 92195 Meudon, France
³ Environmental Sensing & Network Group, NICT, 4-2-1 Nukui-kita, Koganei, Tokyo 184-8795, Japan
⁴ STFC Rutherford Appleton Laboratory, Harwell Innovation Campus, Didcot, OX11 0QX, UK
⁵ California Institute of Technology, Pasadena, CA 91125, USA
⁶ Space Research Centre, Polish Academy of Sciences, Warsaw, Poland
⁷ Rosetta Science Operations Centre, European Space Astronomy Centre, European Space Agency, Spain
⁸ Instituto de Astrofísica de Andalucía (CSIC), Spain
⁹ Instituut voor Sterrenkunde, Katholieke Universiteit Leuven, Belgium
¹⁰ DLR, German Aerospace Centre, Bonn-Oberkassel, Germany
¹¹ Astronomy Department, University of Michigan, USA
¹² Université de Bordeaux, Laboratoire d'Astrophysique de Bordeaux, France
¹³ Laboratory of Molecular Astrophysics, CAB-CSIC, INTA, Spain
¹⁴ Sterrenkundig Instituut Anton Pannekoek, University of Amsterdam, Science Park 904, 1098 Amsterdam, The Netherlands
¹⁵ LERMA, Observatoire de Paris, France
¹⁶ Max-Planck-Institut für extraterrestrische Physik, Giessenbachstraße, 85748 Garching, Germany
¹⁷ Bluesky Spectroscopy, Lethbridge, Canada
¹⁸ SRON Netherlands Institute for Space Research, Landleven 12, 9747 AD, Groningen, The Netherlands
¹⁹ Leiden Observatory, University of Leiden, The Netherlands
²⁰ Atacama Large Millimeter/Submillimeter Array, Joint ALMA Office, Santiago, Chile
²¹ Institute d'Astrophysique et de Geophysique, Université de Liège, Belgium
²² Science Centre, European Space Astronomy Centre, ESA, PO Box 78, 28691 Villanueva de la Cañada, Madrid, Spain
²³ Department of Physics and Astronomy, University of Lethbridge, Canada
²⁴ Physikalisches Institut, University of Bern, Switzerland
²⁵ KOSMA, I. Physik. Institut, Universität zu Köln, Zülpicher Str. 77, 50937 Köln, Germany
²⁶ Jet Propulsion Laboratory, Caltech, Pasadena, CA 91109, USA

Received: 5 June 2010
Accepted: 6 July 2010

Abstract

We report on an initial analysis of Herschel/HIFI observations of hydrogen chloride (HCl), hydrogen peroxide (H₂O₂), and molecular oxygen (O₂) 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 O₂ and determined upper limits of 200 ppt for HCl and 2 ppb for H₂O₂. Radiative transfer model calculations indicate that the vertical profile of O₂ may not be constant. Photochemical models determine the lowest values of H₂O₂ to be around L_s ~ 75° but overestimate the volume mixing ratio compared to our measurements.