A measurement of the 362 GHz absorption line of Mars atmospheric H2O2

• Published in: Icarus (New York, N.Y. 1962) Vol. 168; no. 1; pp. 116 - 121
• Main Authors: CLANCY, R. T, SANDOR, B. J, MORIARTY-SCHIEVEN, G. H
• Format: Journal Article
• Language: English
• Published: San Diego, CA Elsevier 01-03-2004
• Subjects: Astronomy; Chemical composition; Earth, ocean, space; Exact sciences and technology; Mars; Planetary, asteroid, and satellite characteristics and properties; Planets, their satellites and rings. Asteroids; Solar system; Planetary atmospheres; Absorption line; Infrared spectroscopy; Hydrogen peroxide; Mars planet; Standard model; Abundance; Chemical composition; Radiative transfer; Absorption spectra; Mixing ratio; Photochemistry
• ISSN: 0019-1035; 1090-2643
• DOI: 10.1016/j.icarus.2003.12.003

The 362.156 GHz absorption spectrum of H2O2 in the Mars atmosphere was observed on September 4 of 2003, employing the James Clerk Maxwell Telescope (JCMT) sub-millimeter facility on Mauna Kea, Hawaii. Radiative transfer analysis of this line absorption yields an average volume mixing ratio of 18 +/-0.4 ppbv within the lower (0-30 km) Mars atmosphere, in general accordance with standard photochemical models (e.g. Nair et al. 1994, Icarus 111, 124-150). Our derived H2O2 abundance is roughly three times greater than the upper limit retrieved by Encrenaz et al. (2002, Astron. Astrophys. 396, 1037-1044) from infrared spectroscopy, although part of this discrepancy may result from the different solar longitudes (L(s)) of observation. Aphelion-to-perihelion thermal forcing of the global Mars hygropause generates substantial ( > 200 percent) increases in HO(x) abundances above about 10 km altitudes between the L(s) = 112 period of the Encrenaz et al. upper limit measurement and the current L(s) = 250 period of detection (Clancy and Nair, 1996, J. Geophys. Res. 101, 12785-12590). The observed H2O2 line absorption weakens arguments for non-standard homogeneous (Encrenaz et al. 2002, Astron. Astrophys. 396, 1037-1044) or heterogeneous (Krasnopolsky, 2003a, J. Geophys. Res. 108; 2003b, Icarus 165, 315-325) chemistry, which have been advocated partly on the basis of infrared (8-micron) non-detections for Mars H2O2. Observation of Mars H2O2 also represents the first measurement of a key catalytic specie in a planetary atmosphere other than our own.