Search

International audience; A new UV spectral imaging dataset of Mars global images is being obtained by the Imaging Ul- traViolet Spectrograph (IUVS) on the Mars Atmos- phere and V olatile Evolution mission (MA VEN). Of particular interest for atmospheric studies are spec- trally-resolved mid-UV datacubes as shown in Fig- ure 1. Clouds, haze, dust and ozone can all be detect- ed and quantified through image analysis and re- trieval. IUVS observations are the only MAVEN data capable of probing below the spacecraft alti- tude, and provide an important link between the denser atmosphere and escape processes which are MAVEN’s primary focus (Jakosky et al. 2015).

International audience; The Imaging Ultraviolet Spectrograph (IUVS) aboard the Mars Atmosphere and Volatile EvolutioN (MAVEN) mission has systematically observed the Martian oxygen exosphere for nearly one Martian year now. The OI 130.4 nm resonance scattering line is observed all the time at the dayside providing unprecedented information on the oxygen content of the Martian upper atmosphere. These variations are important to understand the chemistry, dynamics, energetics and escape processes of the Martian upper atmosphere. Using a radiative transfer model, we have estimated the amount of oxygen in the Martian exosphere needed to reproduce the observations of IUVS during the first Martian year of the mission. In this work, we will present the seasonal variations of the exospheric oxygen density derived from this set of observations and discussed these variations in the frame of global models of the Martian upper atmosphere.

International audience; The Imaging Ultraviolet Spectrograph (IUVS) on NASA's Mars Atmosphere and Volatile Evolution (MAVEN) mission observed the Martian upper atmosphere in late 2015 (Ls ~ 70) and early 2016 (Ls ~ 150). Although designed to measure the dayglow between 90-200 km IUVS also scans the limb down to 60 km, where solar scattered light dominates the mid-ultraviolet (MUV) signal. Occasionally, this MUV light shows enhanced scattering between 60-90 km indicating the presence of aerosols in the mesosphere. We quantify the solar scattering for each daylight scan obtained between October and December, 2015 and between April and June, 2016. We then identify over 100 scans of enhanced scattering between 60-90 km and assemble them both geographically and diurnally. The geographical distribution of the enhancements in 2015 is preferentially located near the equator, consistent with previous observations of mesospheric clouds for this part of the season. A wave three pattern in equatorial cloud occurrence suggests forcing from a non-migrating tide, possibly linked to the longitudinal variation of Mars surface topography. At the same time, there are indications of a diurnal variation such that the clouds seen in 2015 and 2016 are preferentially observed in the early morning, between 0600-0900 local solar time. This suggests an important role for a migrating temperature tide controlling the formation of Martian mesospheric clouds.

We have developed a model to calculate the emission intensities of various vibrational transitions of N$_2$ triplet band and Lyman-Birge-Hopfield (LBH) band emissions in the dayglow of Pluto for solar minimum, moderate, and maximum conditions. The calculated overhead intensities of Vegard-Kaplan ($ A^3\Sigma_u^+ - X^1\Sigma^+_g $), First Positive ($ B^3\Pi_g - A^3\Sigma^+_u $), Second Positive ($ C^3\Pi_u - B^3\Pi_g $), Wu-Benesch ($W^3\Delta_u - B^3\Pi_g$), Reverse First Positive, and LBH ($a^1\Pi_g$-- $X^1\Sigma^+_g$) bands of N$_2$ are 17 (74), 14.8 (64), 2.4 (10.8), 2.9 (12.7), 2.9 (12.5), and 2.3 (10) R, respectively, for solar minimum (maximum) condition. We have predicted the overhead and limb intensities of VK (150-190 nm) and LBH (120-190 nm) bands of N$_2$ on Pluto for the New Horizons (NH) flyby condition that can be observed by Alice: the ultraviolet imaging spectrograph also know as P-Alice. The predicted limb intensities of VK and LBH bands peak at radial distance of $ \sim$2000 km with the value of about 5 (13) and 9.5 (22) R for solar zenith angle 60$ ^\circ $ (0$ ^\circ $), respectively. We have also calculated overhead and limp intensities of few prominent transition of CO Fourth Positive bands for NH flyby condition., Comment: 7 pages, 5 figures, 2 tables

Present study deals with the model calculations of CO Cameron band and CO2+ ultraviolet doublet emissions in the dayglow of Venus. The overhead and limb intensities of CO Cameron band and CO2+ UV doublet emissions are calculated for low, moderate, and high solar activity conditions. Using updated cross sections, the impact of dierent e-CO cross section for Cameron band production is estimated. The electron impact on CO is the major source mechanism of Cameron band, followed by electron and photon impact dissociation of CO2. The overhead intensities of CO Cameron band and CO2+ UV doublet emissions are about a factor of 2 higher in solar maximum than those in solar minimum condition. The effect of solar EUV flux models on the emission intensity is ~30-40% in solar minimum condition and ~2-10% in solar maximum condition. At the altitude of emission peak (135 km), the model predicted limb intensity of CO Cameron band and CO2+ UV doublet emissions in moderate (F10.7 = 130) solar activity condition is about 2400 and 300 kR, respectively, which is in agreement with the very recently published SPICAV/Venus Express observation. The model limb intensity profiles of CO Cameron band and CO2+ UV doublet are compared with SPICAV observation. We also calculated intensities of N2 Vegard-Kaplan UV bands and OI 2972 {\AA} emissions during moderate and high solar activity conditions., Comment: 12 pages, 10 figures. In Journal of Geophysical Research, 2013