References of "Gérard, Jean-Claude"
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See detailA nearly corotating long lasting auroral spiral at Saturn
Palmaerts, Benjamin ULiege; Yao, Zhonghua ULiege; Sergis, N. et al

Poster (2019, June 04)

The main ultraviolet auroral emission at Saturn consists of multiple structures of various sizes forming a discontinuous ring of emissions around Saturn’s poles. For decades, it is known that the main ... [more ▼]

The main ultraviolet auroral emission at Saturn consists of multiple structures of various sizes forming a discontinuous ring of emissions around Saturn’s poles. For decades, it is known that the main emission is occasionally organized in a global spiral surrounding the pole. In August 2016, the Ultraviolet Imaging Spectrograph (UVIS) on board the Cassini spacecraft proceeded to a 7h-long imaging of Saturn’s northern aurora. During this observing sequence, the main emission displayed a spiral wrapping around the pole by more than 370° in longitude. The spiral was in rotation around the pole at ~90% of rigid corotation, which is an unusually high velocity for extended auroral structures. A spiral was again observed during a shorter UVIS sequence, sixteen hours after the end of the first sequence. Simultaneously to the first UVIS sequence, imaging of the energetic neutral atom (ENA) emissions revealed a hot plasma population in the same local time sector as the extremity of the UV spiral. The leading edge of the plasma population follows the spiral structure around the planet. This correspondence suggests that the presence of the hot plasma distorted the magnetospheric current system, resulting in the spiral shape of the main emission. Furthermore, simultaneous in-situ measurements of the ion fluxes exhibit enhancements recurring every ~10.5 hours. The nearly corotating aurora, ENA emissions and ions revealed by this multi-instrument dataset are likely three signatures of a magnetosphere-ionosphere coupling current system and of the associated hot plasma population corotating with the planet. [less ▲]

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See detailMAVEN‐IUVS observations of the CO2+ UV doublet and CO Cameron bands in the Martian thermosphere: Aeronomy, seasonal and latitudinal distribution.
Gérard, Jean-Claude ULiege; Gkouvelis, Leonardos ULiege; Ritter, Birgit ULiege et al

in Journal of Geophysical Research. Space Physics (2019)

We analyze two Martian years of dayglow measurements of the CO Cameron bands and the CO2+ ultraviolet doublet (UVD) at 298-299 nm with the Imaging UltraViolet Spectrograph on board the Maven orbiter. We ... [more ▼]

We analyze two Martian years of dayglow measurements of the CO Cameron bands and the CO2+ ultraviolet doublet (UVD) at 298-299 nm with the Imaging UltraViolet Spectrograph on board the Maven orbiter. We show that the altitude and the brightness of the two emissions peaks are strongly correlated, although data were collected over a wide range of latitudes and seasons. veraged limb profiles are presented and compared with numerical simulations based on updated calculations of the production of the CO (a3Π) and the CO2+ (B 2Σ) states. The model simulations use the solar flux directly measured on board MAVEN with the Extreme Ultraviolet Monitor (EUVM) and the neutral densities provided by the Mars Climate Database (MCD) version 5.3, adapted to the conditions of the observations. We show that the altitude and the shape of the sample limb profiles are well reproduced using the MCD neutral atmosphere. The simulated peak intensities of the CO2+ UVD and Cameron bands are in good agreement considering the uncertainties on the excitation cross sections and the calibration of the IUVS and EUVM instruments. No significant adjustment of the electron impact cross section on CO2 to produce the a3Π state is needed. Seasonal-latitudinal maps of the Cameron and UVD peak altitude observed during two Martian years show variations as large as 23 km. Model simulations of the amplitude of these changes are in fair agreement with the observations except during the southern summer dust period (Ls = 270°-320°) when the calculated rise of the dayglow layer is underestimated. [less ▲]

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See detailCharacteristics of Mars UV dayglow emissions from atomic oxygen at 130.4 and 135.6 nm: MAVEN/IUVS limb observations and modeling.
Ritter, Birgit ULiege; Gérard, Jean-Claude ULiege; Gkouvelis, Leonardos ULiege et al

in Journal of Geophysical Research. Space Physics (2019)

We present an overview of two Martian years oxygen dayglow limb observations of the ultraviolet (UV) emissions at 130.4 nm and 135.6 nm. The data have been collected with the IUVS instrument on board the ... [more ▼]

We present an overview of two Martian years oxygen dayglow limb observations of the ultraviolet (UV) emissions at 130.4 nm and 135.6 nm. The data have been collected with the IUVS instrument on board the MAVEN spacecraft. We use solar flux measurements of EUVM on board MAVEN to remove the solar induced variation and show the variations of the maximum limb brightness and altitude with season, SZA and latitude, which reflects the strong variability of the Martian atmosphere. The 130.4 and 135.6 nm peak brightness and altitudes are strongly correlated and behave similarly. Both emissions are modeled for selected data using Monte Carlo codes to calculate emissions arising from electron impact on O and CO2. Additional radiative transfer calculations are made to analyze the optically thick 130.4 nm emission. Model atmospheres from the Mars Climate Database serve as input. Both simulated limb profiles are in good agreement with the observations despite some deviations. We furthermore show that the observed 130.4 nm brightness is dominated by resonance scattering of the solar multiplet with a contribution (15-20%) by electron impact on O. Over 95% of the excitation at 135.6 nm arises from electron impact on O. Simulations indicate that the limb brightness is dependent on the oxygen and CO2 content, while the peak emission altitude is mainly driven by the CO2 content because of absorption processes. We deduce [O]/[CO2] mixing ratios of 3.1% and 3.0% at 130 km for datasets collected at LS=350° in Martian years 32 and 33. [less ▲]

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See detailMartian dust storm impact on atmospheric H 2 O and D/H observed by ExoMars Trace Gas Orbiter
Vandaele, A. C.; Korablev, O.; Daerden, F. et al

in Nature (2019), 568

Global dust storms on Mars are rare 1,2 but can affect the Martian atmosphere for several months. They can cause changes in atmospheric dynamics and inflation of the atmosphere 3 , primarily owing to ... [more ▼]

Global dust storms on Mars are rare 1,2 but can affect the Martian atmosphere for several months. They can cause changes in atmospheric dynamics and inflation of the atmosphere 3 , primarily owing to solar heating of the dust 3 . In turn, changes in atmospheric dynamics can affect the distribution of atmospheric water vapour, with potential implications for the atmospheric photochemistry and climate on Mars 4 . Recent observations of the water vapour abundance in the Martian atmosphere during dust storm conditions revealed a high-altitude increase in atmospheric water vapour that was more pronounced at high northern latitudes 5,6 , as well as a decrease in the water column at low latitudes 7,8 . Here we present concurrent, high-resolution measurements of dust, water and semiheavy water (HDO) at the onset of a global dust storm, obtained by the NOMAD and ACS instruments onboard the ExoMars Trace Gas Orbiter. We report the vertical distribution of the HDO/H 2 O ratio (D/H) from the planetary boundary layer up to an altitude of 80 kilometres. Our findings suggest that before the onset of the dust storm, HDO abundances were reduced to levels below detectability at altitudes above 40 kilometres. This decrease in HDO coincided with the presence of water-ice clouds. During the storm, an increase in the abundance of H 2 O and HDO was observed at altitudes between 40 and 80 kilometres. We propose that these increased abundances may be the result of warmer temperatures during the dust storm causing stronger atmospheric circulation and preventing ice cloud formation, which may confine water vapour to lower altitudes through gravitational fall and subsequent sublimation of ice crystals 3 . The observed changes in H 2 O and HDO abundance occurred within a few days during the development of the dust storm, suggesting a fast impact of dust storms on the Martian atmosphere. © 2019, The Author(s), under exclusive licence to Springer Nature Limited. [less ▲]

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See detailNo detection of methane on Mars from early ExoMars Trace Gas Orbiter observations
Korablev, O.; Vandaele, A. C.; Montmessin, F. et al

in Nature (2019), 568

The detection of methane on Mars has been interpreted as indicating that geochemical or biotic activities could persist on Mars today 1 . A number of different measurements of methane show evidence of ... [more ▼]

The detection of methane on Mars has been interpreted as indicating that geochemical or biotic activities could persist on Mars today 1 . A number of different measurements of methane show evidence of transient, locally elevated methane concentrations and seasonal variations in background methane concentrations 2–5 . These measurements, however, are difficult to reconcile with our current understanding of the chemistry and physics of the Martian atmosphere 6,7 , which—given methane’s lifetime of several centuries—predicts an even, well mixed distribution of methane 1,6,8 . Here we report highly sensitive measurements of the atmosphere of Mars in an attempt to detect methane, using the ACS and NOMAD instruments onboard the ESA-Roscosmos ExoMars Trace Gas Orbiter from April to August 2018. We did not detect any methane over a range of latitudes in both hemispheres, obtaining an upper limit for methane of about 0.05 parts per billion by volume, which is 10 to 100 times lower than previously reported positive detections 2,4 . We suggest that reconciliation between the present findings and the background methane concentrations found in the Gale crater 4 would require an unknown process that can rapidly remove or sequester methane from the lower atmosphere before it spreads globally. [less ▲]

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See detailH3+ characteristics in the Jupiter atmosphere as observed at limb with Juno/JIRAM
Migliorini, Alessandra; Dinelli, B.M.; Moriconi, M.L. et al

in Icarus (2019), 329

NASA’s Juno spacecraft has been orbiting Jupiter since August 2016, providing unprecedented insights into the giant planet’s atmosphere. The Jupiter Infrared Auroral Mapper (JIRAM) experiment on board ... [more ▼]

NASA’s Juno spacecraft has been orbiting Jupiter since August 2016, providing unprecedented insights into the giant planet’s atmosphere. The Jupiter Infrared Auroral Mapper (JIRAM) experiment on board Juno has made spectroscopic observations of the trihydrogen cation (H3+) emissions in both northern and southern auroral regions (Dinelli et al. 2017; Adriani et al. 2017; Mura et al. 2017) and at mid-to-low latitudes (this paper). Observations targeting the limb of the planet from 60° North to 60° South latitudes were acquired with JIRAM’s spectrometer in August 2016 and March 2017. We use these observations to characterize, for the first time, the vertical distribution of the H3+ emissions as a function of latitude across Jupiter’s sunlit face dayside. H3+ emission features in the 3-4 μm spectral band were used to retrieve the H3+ volume mixing ratio (VMR) and atmospheric temperatures as a function of altitude. The H3+ density profile has a quasi-symmetric distribution with latitude, decreasing from 5×105 cm-3 at 500 km altitude above the 1-bar level to 2×105 cm-3 at 650 km (column densities of 3.5×1013 cm-2 to 1.4×1013 cm-2, assuming a 700 km column depth; altitudes are referenced to 1-bar pressure level). The H3+ VMR is higher in the Southern hemisphere than in the North with values at 500 km altitude of ~4×10-4 ppmv at 40°N and ~8×10-4 ppmv at 40°S. Retrieved temperatures increase almost monotonically with increasing altitude, hovering around 400 K at 300 km and greater than 900 K at about 700 km. [less ▲]

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See detailUV Study of the Fourth Positive Band System of CO and OI 135.6 nm From Electron Impact on CO and CO2
Ajello, J. M.; Malone, C. P.; Evans, J. S. et al

in Journal of Geophysical Research: Space Physics (2019), 124

We have measured the 30 and 100 eV far ultraviolet (FUV) emission cross sections of the optically allowed Fourth Positive Group (4PG) band system (A 1 Π → X 1 Σ + ) of CO and the optically forbidden O (5S ... [more ▼]

We have measured the 30 and 100 eV far ultraviolet (FUV) emission cross sections of the optically allowed Fourth Positive Group (4PG) band system (A 1 Π → X 1 Σ + ) of CO and the optically forbidden O (5S  →  3P) 135.6 nm atomic transition by electron-impact-induced-fluorescence of CO and CO2 . We present a model excitation cross section from threshold to high energy for the A 1Π state, including cascade by electron impact on CO. The A 1Π state is perturbed by triplet states leading to an extended FUV glow from electron excitation of CO. We derive a model FUV spectrum of the 4PG band system from dissociative excitation of CO2 , an important process observed on Mars and Venus. Our unique experimental setup consists of a large vacuum chamber housing an electron gun system and the Mars Atmosphere and Volatile EvolutioN (MAVEN) mission Imaging Ultraviolet Spectrograph optical engineering unit, operating in the FUV (110–170 nm). The determination of the total OI ( 5S o ) at 135.6 nm emission cross section is accomplished by measuring the cylindrical glow pattern of the metastable emission from electron impact by imaging the glow intensity about the electron beam from nominally zero to ~400 mm distance from the electron beam. The study of the glow pattern of O i (135.6 nm) from dissociative excitation of CO and CO 2 indicates that the OI (5 S) state has a kinetic energy of ~1 eV by modeling the radial glow pattern with the published lifetime of 180 μs for the OI (5 S) stat. [less ▲]

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See detailLyman-α emission in the Martian proton aurora: Line profile and role of horizontal induced magnetic field
Gérard, Jean-Claude ULiege; Hubert, Benoît ULiege; Ritter, Birgit ULiege et al

in Icarus (2019), 321

Enhancements of the dayside Lyman-α emission by as much as ∼50% have been observed between 120 and 130 km in the lower Martian thermosphere from the Mars Express and MAVEN satellites, usually following ... [more ▼]

Enhancements of the dayside Lyman-α emission by as much as ∼50% have been observed between 120 and 130 km in the lower Martian thermosphere from the Mars Express and MAVEN satellites, usually following solar events such as coronal mass ejections and corotating interaction regions. They have been assumed to be optical signatures of proton aurora related to an increase in the solar wind proton flux hitting Mars’ bow shock. We present model simulations of the Lyman-α line profiles at different altitudes. These are partly guided by in situ measurements of the energy spectrum of protons in the magnetosheath region by the SWIA instrument on board the MAVEN spacecraft. We show that the auroral Lyman-α line profile is significantly broader than the hydrogen core of the planetary thermal H atom. Consequently, most of the auroral emission is produced outside the optically thick hydrogen core and creates the observed intensity enhancement. Simulations with incident energetic hydrogen atoms (H ENAs) produce a somewhat broader line profile. Monte Carlo calculations are made separately for incident solar wind protons and H ENAs produced by charge exchange in the hydrogen corona. Absorption by CO2 along the line of sight significantly affects the intensity distribution in the lower thermosphere. The calculated altitude of the peak emission for both types of incident particles is consistent with the observed characteristics of the proton aurora. We show that the presence of a horizontal induced magnetic field somewhat increases the line width and decreases the altitude of the emission peak as a consequence of the magnetic barrier effect on proton precipitation. The brightness of the Lyman-α emission also drops as a result of increased magnetic shielding of the protons. [less ▲]

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See detailObservations of satellite footprints in Jupiter's Aurorae
Mura, A.; Adriani, A.; Altieri, F. et al

Conference (2018, December 12)

JIRAM (Jovian Infrared Auroral Mapper) on board Juno is an imager/spectrometer in the 2-5 um range. One imaging channel is designed to study the Jovian H3+ auroral emissions. Its high angular resolution ... [more ▼]

JIRAM (Jovian Infrared Auroral Mapper) on board Juno is an imager/spectrometer in the 2-5 um range. One imaging channel is designed to study the Jovian H3+ auroral emissions. Its high angular resolution, combined with the unique vantage point provided by Juno, allows JIRAM to observe the aurorae in unprecedented detail. Here we present the results from ~2 years of observations of the auroral footprints of the Galilean moons. These are bright spots and associated tail that appear in Jupiter’s ionosphere at the base of the magnetic field lines which sweep past Io, Europa, and Ganymede. The moons are obstacles in the path of Jupiter’s rapidly rotating magnetospheric plasma, and the resulting electromagnetic interaction launches Alfvén waves along the magnetic field towards Jupiter, where intense electron bombardment of the hydrogen atmosphere causes it to glow. Recent observations reveal for the first time that the footprint of Io is comprised of a regularly spaced array of emission features, extending downstream of the leading footprint. Contrary to the larger spots seen in lower resolution images, the small scale of these multiple features (~100 km) is incompatible with the simple paradigm of multiple Alfvén wave reflections. Additionally, observations of Io’s trailing tail well downstream of the main footprint reveal a pair of closely spaced parallel arcs, previously unresolved. The temperatures of the main spot and tail, retrieved with the JIRAM spectrometer, are lower than the main auroral oval. This could indicate that the emission is located at a deeper level, possibly caused by higher energy electrons. Ganymede’s footprint spots (main and secondary) appear as a pair of emission features that provide a remote measure of the size Ganymede’s magnetosphere, mapped from its distant orbit onto Jupiter’s magnetosphere. [less ▲]

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See detailAnalytic methods for the Abel transform of exponential functions describing planetary and cometary atmospheres.
Hubert, Benoît ULiege; Munhoven, Guy ULiege; Opitom, Cyrielle et al

Poster (2018, December 11)

Remote sensing of planetary and cometary atmosphere is one of the most important source of data and knowledge of the gas layers surrounding the celestial objects of our solar system, including our own ... [more ▼]

Remote sensing of planetary and cometary atmosphere is one of the most important source of data and knowledge of the gas layers surrounding the celestial objects of our solar system, including our own planet. Most of the instruments used up to now and that will be used in a near future study the emission of radiations directly produced by the atmosphere. Under optically thin conditions, this observation method provides the local volume emission rate (VER) originating from the atmosphere, integrated along the full line of sight (l.o.s.) of the instrument. Under a spherical or cylindrical symmetry assumption, the l.o.s. integration of the VER takes the form of the Abel transform of the vertical VER profile. The simplest analytical functions representing VER profiles in real planetary and cometary atmosphere include an exponential function of the altitude (or radial distance), giving the isothermal profile for a planet and the Haser model for a coma. The Abel transform of these functions can be computed analytically using combinations of special functions. Retrieving the vertical (radial) profile of the VER does however require to invert the observed Abel transform to account for possible departures from these idealized analytical expressions, so that indefinite integrals defined from the Abel integral (which we will call indefinite Abel transforms) are needed (or numerical integrations need to be performed). In this study, we present a new method to produce a workable series development allowing accurate computation of the indefinite Abel transforms that appear in the study of optically thin emissions of planetary and cometary atmospheres. Indeed, taking the Taylor series development of the exponential function to reduce the problem to a series of indefinite Abel transforms of polynomial functions (which can be carried analytically) does not work. It leads to the computation of the difference of large, nearly equal numbers, which cannot be done accurately. Our method rather relies on an appropriate series development of the Jacobian of the Abel transform. We show that the computation can be done reliably up to near machine precision, and that accuracy control can be enforced for tailored applications. Possible applications are considered, that include the study of comas and of the upper atmosphere of Mars and the Earth [less ▲]

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See detailFlying through a Dawn Storm : an analysis of Juno-UVS images during PJ11
Bonfond, Bertrand ULiege; Gladstone, G. R.; Grodent, Denis ULiege et al

Poster (2018, December 11)

Auroral dawn storms at Jupiter are spectacular brightenings of the dawn arc of the main emission. These events are relatively rare, but they account for some of the brightest aurorae ever observed at ... [more ▼]

Auroral dawn storms at Jupiter are spectacular brightenings of the dawn arc of the main emission. These events are relatively rare, but they account for some of the brightest aurorae ever observed at Jupiter. An event with a total power emitted by the UV aurora in excess of 8.5 TW was even observed by Hisaki and the Hubble Space Telescope on May 21st 2016, during Juno’s approach of Jupiter. On February 7th 2018 (perijove 11, or PJ11), Juno’s ultraviolet imaging spectrograph, called Juno-UVS, observed the development of such a dawn storm, right before Juno flew right through the magnetic field line connected to this feature. The storm started around 13:15 UT as a limited enhancement of the main emission around midnight before slowly migrating and expanding on the dusk flank. As the brightness increased, the arc began to thicken and fork into two separate arcs. Simultaneously, the signatures of methane absorption of the UV light progressively intensified, indicative of a precipitation of increasingly energetic particles. Then, around 18:15 UT, Juno entered the field lines feeding the dawn storm. The remote auroral observations thus provide extremely valuable context information for the in-situ radio waves, particle and magnetic field observations gathered at this time. [less ▲]

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See detailMartian upper-atmosphere circulation and tides revealed through MAVEN/IUVS observations of nitric oxide nightglow
Schneider, N.M.; Stiepen, A.; Milby, Z. et al

Conference (2018, December 11)

The nitric oxide δ and γ bands are ultraviolet emissions which reflect the production rate of nitric oxide (NO) from the recombination of excited nitrogen and oxygen atoms. We use it as a tracer of the ... [more ▼]

The nitric oxide δ and γ bands are ultraviolet emissions which reflect the production rate of nitric oxide (NO) from the recombination of excited nitrogen and oxygen atoms. We use it as a tracer of the dynamics between Mars’ upper- and middle-atmospheres, particularly of day-to-night and summer-to-winter pole circulation. We analyse this rate as it varies over Mars’ surface in mission-long aggregations and local-time divisions. Our data were gathered by the Mars Atmosphere and Volatile Evolution (MAVEN) mission’s Imaging UltraViolet Spectrograph (IUVS) and span different seasonal conditions and latitudes. The data span allows a limited comparison between two subsequent Mars years. In our previous study from a limited dataset of atmospheric limb scans (Stiepen 2017, doi:10.1002/2016JA023523), we discovered a wave-3 structure to the nightglow at equatorial latitudes. For this study, we use scans taken of the full disk of Mars as seen at apoapse over 1.25 Mars years. We observe the same wave-3 structure, and find strong seasonal and local-time dependencies on position and brightness. We also discovered a wave-2 structure in northern polar regions that persists through all observed local times and seasons. We compare our observations to model calculations from the LMD-MGCM. We find the model generally under-predicts the brightness of the nightglow at all sub-polar latitudes, suggesting it over-estimates the efficiency of atomic transport to the poles. However, we also find that the model reproduces the observed equatorial wave-3 and polar wave-2 structures. We identify the dominant atmospheric tide component of the equatorial wave-3 structure and analysis of the local-time dependencies of the wave structures and the brightness across all latitudes. We also compare the observed polar nightglow wave structure to contemporaneous dayside ozone distributions also measured by IUVS. [less ▲]

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See detailThe O(1S) 297.2 nm dayglow emission: a tracer of CO2 density variations in the Martian lower thermosphere
Gkouvelis, Leonardos ULiege; Gérard, Jean-Claude ULiege; Ritter, Birgit ULiege et al

in Journal of Geophysical Research. Planets (2018), 123

The O(1S) metastable atoms can radiatively relax by emitting airglow at 557.7 and 297.2 nm. The latter one has been observed with the Imaging Ultraviolet Spectrograph onboard the Mars Atmosphere and ... [more ▼]

The O(1S) metastable atoms can radiatively relax by emitting airglow at 557.7 and 297.2 nm. The latter one has been observed with the Imaging Ultraviolet Spectrograph onboard the Mars Atmosphere and Volatile Evolution Mars orbiter since 2014. Limb profiles of the 297.2-nm dayglow have been collected near periapsis with a spatial resolution of 5 km or less. They show a double-peak structure that was previously predicted but never observed during earlier Mars missions. The production of both 297.2-nm layers is dominated by photodissociation of CO2. Their altitude and brightness is variable with season and latitude, reflecting changes in the total column of CO2 present in the lower thermosphere. Since the lower emission peak near 85 km is solely produced by photodissociation, its peak is an indicator of the unit optical depth pressure level and the overlying CO2 column density. Its intensity is directly controlled by the Lyman-α solar flux reaching the Martian upper atmosphere. We take advantage of the Lyman-α flux measurements of the solar Extreme Ultraviolet Monitor instrument onboard Mars Atmosphere and Volatile Evolution to model the observed OI 297.2-nm limb profiles. For this, we combine photodissociation sources with chemical processes and photoelectron impact excitation. To determine the relative importance of the excitation processes, we apply the model to the atmospheric structure measured by the Viking 1 lander before applying it to a model atmosphere. We find very good agreement with the lower peak structure and intensity if the CO2 density provided by the Mars Climate Database is scaled down by a factor between 0.50 and 0.66. We also determine that the previously uncertain quantum yield for production of O(1S) atoms by photodissociation of CO2 at Lyman-α wavelength is about 8%. [less ▲]

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See detailObservations of Jupiter by the Juno Ultraviolet Spectrograph (Juno-UVS)
Greathouse, T. E.; Gladstone, G.R.; Hue, V. et al

Conference (2018, September 20)

We present an overview of the science performed by Juno’s Ultraviolet Spectrograph, UVS, over the first 11 successful perijove sequences performed since orbital insertion on July 4th, 2016. We will ... [more ▼]

We present an overview of the science performed by Juno’s Ultraviolet Spectrograph, UVS, over the first 11 successful perijove sequences performed since orbital insertion on July 4th, 2016. We will discuss the measured local time dependence of Jupiter’s polar auroral emissions, simultaneous UV and H3+ observations and their correlations or lack thereof, evolution and morphology of Io’s magnetic footprint in Jupiter’s atmosphere, measurements concerning the spatial and temporal variation of high energy particles (>7 MeV) in the polar regions of Jupiter’s magnetosphere, and finally the production of a dataset that could be used to produce an all sky UV stellar atlas at wavelengths between 70 and 205 nm. [less ▲]

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See detailCO2 variations in the Martian lower thermosphere from IUVS-MAVEN airglow observations.
Gkouvelis, Leonardos; Gérard, Jean-Claude ULiege; Ritter, Birgit ULiege et al

Conference (2018, September 17)

IUVS-MAVEN limb observations have been performed since 2014. We have analyzed almost four years of observations focusing on the O(1S) 297.2 nm dayglow emission line. We have developed an automatic ... [more ▼]

IUVS-MAVEN limb observations have been performed since 2014. We have analyzed almost four years of observations focusing on the O(1S) 297.2 nm dayglow emission line. We have developed an automatic methodology to retrieve the CO2 column densities near 80 km, a region difficult to probe by other techniques. We present nearly two Martian years of observations of pressure variations at different latitudes and comparisons withMCD model predictions. Generally, the best agreement is reached following scaling down of the MCD values from 0.3 to 0.8 to fit the observations. This result was previously expected on the basis of model comparisons with ultraviolet occultation measurements. [less ▲]

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See detailMars emissions from CO and CO2+: IUVS-MAVEN limb observations and model
Gérard, Jean-Claude ULiege; Gkouvelis, Leonardos ULiege; Ritter, Birgit ULiege et al

Poster (2018, September 17)

The IUVS Ultraviolet spectrograph (McClintock et al. 2014) on board MAVEN has been collecting thousands of airglow (Jain et al. 2015) or auroral (Schneider et al., 2015) limb profiles in the range 120 to ... [more ▼]

The IUVS Ultraviolet spectrograph (McClintock et al. 2014) on board MAVEN has been collecting thousands of airglow (Jain et al. 2015) or auroral (Schneider et al., 2015) limb profiles in the range 120 to 340 nm (Fig. 1) since November 2014. We have analyzed more that three years of airglow observations and compared them to model simulations. MAVEN has been quasi-continuously collecting airglow observations since November 2014, covering more than 1.5 Martian year and various latitudes ranges. The main features are emissions from CO, CO2+, O, N2 and C. In this work, we compare the characteristics of the CO2+ ultraviolet doublet (UVD) limb profiles with model simulations. From this comparison, we derive the CO2 column density above the 120-130 km region. [less ▲]

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See detailA chemical survey of exoplanets with ARIEL
Tinetti, Giovanna; Drossart, Pierre; Eccleston, Paul et al

in Experimental Astronomy (2018)

Thousands of exoplanets have now been discovered with a huge range of masses, sizes and orbits: from rocky Earth-like planets to large gas giants grazing the surface of their host star. However, the ... [more ▼]

Thousands of exoplanets have now been discovered with a huge range of masses, sizes and orbits: from rocky Earth-like planets to large gas giants grazing the surface of their host star. However, the essential nature of these exoplanets remains largely mysterious: there is no known, discernible pattern linking the presence, size, or orbital parameters of a planet to the nature of its parent star. We have little idea whether the chemistry of a planet is linked to its formation environment, or whether the type of host star drives the physics and chemistry of the planet's birth, and evolution. ARIEL was conceived to observe a large number ( 1000) of transiting planets for statistical understanding, including gas giants, Neptunes, super-Earths and Earth-size planets around a range of host star types using transit spectroscopy in the 1.25-7.8 μm spectral range and multiple narrow-band photometry in the optical. ARIEL will focus on warm and hot planets to take advantage of their well-mixed atmospheres which should show minimal condensation and sequestration of high-Z materials compared to their colder Solar System siblings. Said warm and hot atmospheres are expected to be more representative of the planetary bulk composition. Observations of these warm/hot exoplanets, and in particular of their elemental composition (especially C, O, N, S, Si), will allow the understanding of the early stages of planetary and atmospheric formation during the nebular phase and the following few million years. ARIEL will thus provide a representative picture of the chemical nature of the exoplanets and relate this directly to the type and chemical environment of the host star. ARIEL is designed as a dedicated survey mission for combined-light spectroscopy, capable of observing a large and well-defined planet sample within its 4-year mission lifetime. Transit, eclipse and phase-curve spectroscopy methods, whereby the signal from the star and planet are differentiated using knowledge of the planetary ephemerides, allow us to measure atmospheric signals from the planet at levels of 10-100 part per million (ppm) relative to the star and, given the bright nature of targets, also allows more sophisticated techniques, such as eclipse mapping, to give a deeper insight into the nature of the atmosphere. These types of observations require a stable payload and satellite platform with broad, instantaneous wavelength coverage to detect many molecular species, probe the thermal structure, identify clouds and monitor the stellar activity. The wavelength range proposed covers all the expected major atmospheric gases from e.g. H[SUB]2[/SUB]O, CO[SUB]2[/SUB], CH[SUB]4[/SUB] NH[SUB]3[/SUB], HCN, H[SUB]2[/SUB]S through to the more exotic metallic compounds, such as TiO, VO, and condensed species. Simulations of ARIEL performance in conducting exoplanet surveys have been performed - using conservative estimates of mission performance and a full model of all significant noise sources in the measurement - using a list of potential ARIEL targets that incorporates the latest available exoplanet statistics. The conclusion at the end of the Phase A study, is that ARIEL - in line with the stated mission objectives - will be able to observe about 1000 exoplanets depending on the details of the adopted survey strategy, thus confirming the feasibility of the main science objectives. [less ▲]

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