First detection of Mars atmospheric hydroxyl: CRISM Near-IR measurement versus LMD GCM simulation of OH Meinel band emission in the Mars polar winter atmosphere

• Published in: Icarus (New York, N.Y. 1962) N.Y. 1962), 2013-09, Vol.226 (1), p.272-281
• Main Authors: Todd Clancy, R., Sandor, Brad J., García-Muñoz, Antonio, Lefèvre, Franck, Smith, Michael D., Wolff, Michael J., Montmessin, Franck, Murchie, Scott L., Nair, Hari
• Format: Article
• Language: English
• Subjects: Aeronomy; Astrophysics; Atmospheres, Dynamics; Earth and Planetary Astrophysics; Emission; Excitation; Mars; Mars, Atmosphere; Nightglow; Photochemistry; Physics; Quenching; Sciences of the Universe; Spectroscopy; Uncertainty; Winter
• ISSN: 0019-1035; 1090-2643
• DOI: 10.1016/j.icarus.2013.05.035

•The key radical OH is detected for the first time in the Mars atmosphere.•The OH emission appears as near-infrared night glow in the polar winter atmosphere.•The OH Meinel band structure constrains formation and de-excitation pathways.•The observations support current models of Mars atmospheric transport and chemistry. Visible and near-IR Meinel band emissions originate from excited OH in the terrestrial upper atmosphere (Meinel, I.A.B. [1950]. Astrophys. J. 111, 555. http://dx.doi.org/10.1086/145296), and have recently been detected in the Venus nightside upper mesosphere (Piccioni, G. et al. [2008]. Astron. Astrophys. 483, L29–L33. http://dx.doi.org/10.1051/0004-6361:200809761). Meinel band observations support key studies of transport and photochemistry in both of these atmospheres. In the case of Mars, OH regulates the basic stability of the CO2 atmosphere to photolytic decomposition (to CO and O2, e.g. Parkinson, T.D., Hunten, D.M. [1972]. J. Atmos. Sci. 29, 1380–1390. http://dx.doi.org/10.1175/1520-0469(1972)0292.0.CO;2), and yet has never been measured. We present the first detection of Mars atmospheric OH, associated with CRISM near-IR spectral limb observations of polar night Meinel band emissions centered at 1.45 and 2.9μm. Meinel band (1–0), (2–1), and (2–0) average limb intensities of 990±280, 1060±480, and 200±100kiloRayleighs (kR), respectively, are determined for 70–90 NS polar winter latitudes over altitudes of 40–56km. Additional OH bands, such as (3–2), (3–1), and (4–2), present ⩽1σ measurements. Uncertainty in the (4–2) band emission rate contributes to increased uncertainty in the determination of the O2(1Δg) (0–0)/(0–1) band emission ratio A00/A01=47-12+26. An average profile retrieval for Mars OH polar nightglow indicates 45–55km altitude levels for volume emission rates (VER) of 0.4 (2–0) to 2 (1–0, 2–1)×104photons/(cm3s). Similar to polar night O2(1Δg) emission (e.g. Clancy, R.T. et al. [2012]. J. Geophys. Res. (Planets) 117, E00J10. http://dx.doi.org/10.1029/2011JE004018), Meinel OH band emission is supported by upper level, winter poleward transport of O and H in the deep Hadley solsticial circulations of Mars. The retrieved OH emission rates are compared to polar winter OH nightglow simulated by the LMD (Laboratoire de Météorologie Dynamique) photochemical GCM (global climate model), employing detailed photochemistry (e.g. Lefèvre, F., Lebonnois, S., Montmessin, F., Forget, F. [2004]. J. Geophys. Res. (Planets) 109,