Oxygen dayglow observations on Mars by SPICAM IR on Mars-Express

O2(1Δg) dayglow at 1.27 μm reflects the ozone distribution in the Martian atmosphere as a result of ozone photolysis by solar UV radiation. SPICAM IR on Mars-Express performed continuous observations of the O2 dayglow at limb and nadir from 2004 to 2012 with resolving power of 2200. The results of O2(1Δg) observations have been compared with LMD GCM simulation [1-3] to study its seasonal variations and sensitivity to kinetic parameters

O₂(a¹Δ_g) dayglow limb observations on Mars by SPICAM IR on Mars-Express and connection to water vapor distribution

International audienceThe 1.27-μm O2(a1Δg) dayglow on Mars is a product of the ozone photolysis by solar UV radiation. The intensity of the O2(a1Δg) emission rate depends on ozone concentration, atmospheric density and kinetic parameters of involved photochemical reactions. In turn, the distribution of ozone is sensitive to the vertical and spatial distribution of water vapor, which is an effective destructor of O3. SPICAM IR on the Mars-Express mission measures the O2(a1Δg) dayglow with spectral resolving power of 2200. The results of 147 limb observations from 2004 to 2013 are reported. Limb resolution of the instrument is variable and exceeds the scale height of the atmosphere. The slant emission rate reaches a maximum at the high northern latitudes at northern and southern springs Ls=0-50° and 160-190°, respectively and a minimum in middle and low latitudes at southern summer Ls=200-300°. We have compared the SPIVAM O2(a1Δg) limb profiles with the General Circulation Model simulation by the Laboratoire de Meteorologie Dynamique reduced to the vertical resolution of the instrument. The GCM includes the radiative effect of the water clouds and an interactive dust scheme, and well reproduces Martian Climate Sounder (MCS) temperature profiles. The model underestimates the emission for Ls=0-50°, Ls=160-180° and overestimates it from Ls=60° to Ls=150° at high northern latitudes. In the Southern hemisphere the model underestimates the emission for Ls = 170-200° and overestimates it for Ls = 200-230° at high southern latitudes. The disagreement could be related to the water vapor distribution as the model reproduces it. The most recent version of the LMD GCM including microphysical representation of cloud formation taking into account the effect of dust scavenging by water ice clouds gives much better agreement with SPICAM O2(a1Δg) dayglow limb observations. Characterization of the Mars water cycle by GCMs continues to improve, and the observations of the O2(a1Δg) dayglow offer a powerful tool for its validation

Long-term O2 nightglow observations in the polar night on Mars by SPICAM/MEx

International audienceWe will present preliminary results of the O nightglow observations in Northern and Southern hemispheres at different Martian years

The O2 Dayglow Observations with the SPICAM IR Experiment on Mars-Express

International audienc

Long-term nadir observations of the O₂ dayglow by SPICAM IR

International audienceThe O2(a1Δg) dayglow at the 1.27 µm band on Mars is produced by the solar UV photolysis of ozone and quenched in collisions with CO2. The SPICAM IR instrument onboard the Mars Express orbiter observes the O2(a1Δg) emission in the Martian atmosphere starting from 2004. We present a continuous set of O2(a1Δg) dayglow intensities from nadir measurements for six Martian years from the end of MY26 to MY32. Maximum values of the O2(a1Δg) dayglow reaching 31 MR were observed in early northern and southern springs in both hemispheres. Near the equator a spring maximum of 5–8 MR was observed for all years. The emission intensity is minimum in the Southern hemisphere in summer with values of 1–2 MR. Comparison of the data with GCM simulations and simultaneous ozone measurements by SPICAM UV allows to derive the quenching rate (k) of the excited O2 molecules by CO2, k=0.73×10−20 cm3 molecules−1 s−1. The interannual variation of the O2 emission has been studied after applying correction for the local time. The O2(a1Δg) seasonal pattern is rather stable with average year-to-year relative variation of about 21%, in accord with interannual variations detected from the ground (Krasnopolsky, 2013). The most variable region corresponds to northern and southern spring at middle latitudes, coinciding with sublimation of the polar caps in both hemispheres. Southern latitudes also show a high year-to-year variability in summer (Ls=270–330°) relating to the dust activity in this region. A comparison with simultaneous SPICAM water vapor observations shows that the O2(a1Δg) dayglow depends on the water vapor variations, and clearly confirms their anti-correlation, excepting the case of low and middle latitudes in the aphelion period

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

International audienceWe present observations of the O2(a1Δg) nightglow at 1.27 μm on Mars using the SPICAM IR spectrometer onboard of the Mars Express orbiter. In contrast to the O2(a1Δg) dayglow that results from the ozone photodissociation, the O2(a1Δg) 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(a1Δg) nightglow in 2010 indicate that it is about two order of magnitude less intense than the dayglow [ and ]. SPICAM IR sounds the Martian atmosphere in the near-IR range (1-1.7 μm) with the spectral resolution of 3.5 cm-1 in nadir, limb and solar occultation modes. In 2010 the vertical profiles of the O2(a1Δg) nightside emission have been obtained near the South Pole at latitudes of 82-83oS for two sequences of observations: Ls=111-120o and Ls=152-165o. The altitude of the emission maximum varied from 45 km on Ls=111-120o to 38-49 km on Ls=152-165o. 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 1011 to 2.5 1011 cm-3. Comparison with the LMD general circulation model with photochemistry [Lefèvre et al., 2004; 2008] shows that the model reproduces fairly well the O2(a1Δg) emission layer observed by SPICAM when the large field of view (> 20 km on the limb) of the instrument is taken into account