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

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• 作者：R. Todd Clancy ; Brad J. S ; or ; Antonio Garc¨ªa-Mu?oz ; Franck Lef¨¨vre ; Michael D. Smith ; Michael J. Wolff ; Franck Montmessin ; Scott L. Murchie ; Hari Nair
• 关键词：Mars ; Atmosphere ; Aeronomy ; Photochemistry ; Spectroscopy ; Atmospheres ; Dynamics
• 刊名：Icarus
• 出版年：2013
• 出版时间：September-October, 2013
• 年：2013
• 卷：226
• 期：1
• 页码：272-281
• 全文大小：672 K

文摘

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. ), and have recently been detected in the Venus nightside upper mesosphere (Piccioni, G. et al. [2008]. Astron. Astrophys. 483, L29-L33. ). 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. ), 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 2.9 ¦Ìm. Meinel band (1-0), (2-1), and (2-0) average limb intensities of 990 ¡À 280, 1060 ¡À 480, and 200 ¡À 100 kiloRayleighs (kR), respectively, are determined for 70-90 NS polar winter latitudes over altitudes of 40-56 km. Additional OH bands, such as (3-2), (3-1), and (4-2), present ?1¦Ò measurements. Uncertainty in the (4-2) band emission rate contributes to increased uncertainty in the determination of the O₂(¹¦¤_g) (0-0)/(0-1) band emission ratio . An average profile retrieval for Mars OH polar nightglow indicates 45-55 km altitude levels for volume emission rates (VER) of 0.4 (2-0) to 2 (1-0, 2-1) ¡Á 10⁴ photons/(cm³ s). Similar to polar night O₂(¹¦¤_g) emission (e.g. Clancy, R.T. et al. [2012]. J. Geophys. Res. (Planets) 117, E00J10. ), 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 M¨¦t¨¦orologie Dynamique) photochemical GCM (global climate model), employing detailed photochemistry (e.g. Lef¨¨vre, F., Lebonnois, S., Montmessin, F., Forget, F. [2004]. J. Geophys. Res. (Planets) 109, E07004. ) and energy transfer processes (excitation and quenching) developed for Mars Meinel OH band nightglow by Garc¨ªa Mu?oz et al. (Garc¨ªa Mu?oz, A., McConnell, J.C., McDade, I.C., Melo, S.M.L. [2005]. Icarus 176, 75-95). Modeled versus observed OH emission behavior agrees within measurement uncertainties with the assumptions of a Bates-Nicolet (H + O₃) source for excited OH production, and ¡®collisional-cascade¡¯ quenching of the OH vibrational population by CO₂. ¡®Sudden-death¡¯ quenching of excited OH by CO₂ leads to 100¡Á less OH emission than observed. The combined agreement between LMD GCM simulated and CRISM observed O₂(¹¦¤_g) and Meinel OH polar nightglow behaviors represents a significant demonstration of the LMD model capability to couple odd oxygen and hydrogen photochemistry and transport by the Mars global circulation in a realistic fashion.