The O₂ nightglow in the martian atmosphere by SPICAM onboard of Mars-Express

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• 作者：A.A. Fedorovap>ap>p> ; p>p>bp>p> ; p>p>fedorova@iki.rssi.rup> ; F. Lefè ; vrep>cp> ; S. Guslyakovap>ap>p> ; p>p>bp> ; O. Korablevp>ap>p> ; p>p>bp> ; J.-L. Bertauxp>cp> ; F. Montmessinp>cp> ; A. Reberacp>cp> ; B. Gondetp>dp>
• 关键词：Mars ; Atmosphere ; Infrared observations ; Aeronomy
• 刊名：Icarus
• 出版年：2012
• 出版时间：June, 2012
• 年：2012
• 卷：219
• 期：2
• 页码：596-608
• 全文大小：2280 K

文摘

We present observations of the O₂(ap>1p>¦¤_g) nightglow at 1.27 ¦Ìm on Mars using the SPICAM IR spectrometer onboard of the Mars Express orbiter. In contrast to the O₂(ap>1p>¦¤_g) dayglow that results from the ozone photodissociation, the O₂(ap>1p>¦¤_g) nightglow is a product of the recombination of O atoms formed by CO₂ photolysis on the dayside at altitudes higher than 80 km and transported downward above the winter pole by the Hadley circulation. The first detections of the O₂(ap>1p>¦¤_g) nightglow in 2010 indicate that it is about two order of magnitude less intense than the dayglow (Bertaux, J.-L., Gondet, B., Bibring, J.-P., Montmessin, F., Lef¨¨vre, F. [2010]. Bull. Am. Astron. Soc. 42, 1040; Clancy et al. [2010]. Bull. Am. Astron. Soc. 42, 1041). SPICAM IR sounds the martian atmosphere in the near-IR range (1-1.7 ¦Ìm) with the spectral resolution of 3.5 cmp>?p> in nadir, limb and solar occultation modes. In 2010 the vertical profiles of the O₂(ap>1p>¦¤_g) nightside emission have been obtained near the South Pole at latitudes of 82-83¡ãS for two sequences of observations: L_s = 111-120¡ã and L_s = 152-165¡ã. The altitude of the emission maximum varied from 45 km on L_s = 111-120¡ã to 38-49 km on L_s = 152-165¡ã. Averaged vertically integrated intensity of the emission at these latitudes has shown an increase from 0.22 to 0.35 MR. Those values of total vertical emission rate are consistent with the OMEGA observations on Mars-Express in 2010. The estimated density of oxygen atoms at altitudes from 50 to 65 km varies from 1.5 ¡Á 10p>11p> to 2.5 ¡Á 10p>11p> cmp>?p>. Comparison with the LMD general circulation model with photochemistry (Lef¨¨vre, F., Lebonnois, S., Montmessin, F., Forget, F. [2004]. J. Geophys. Res. 109, E07004; Lef¨¨vre et al. [2008]. Nature 454, 971-975) shows that the model reproduces fairly well the O₂(ap>1p>¦¤_g) emission layer observed by SPICAM when the large field of view (>20 km on the limb) of the instrument is taken into account.