References of "Bertaux, J*-L"
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See detailThe 19 Feb. 2016 Outburst of Comet 67P/CG: An ESA Rosetta Multi-Instrument Study
Grün, E.; Agarwal, J.; Altobelli, N. et al

in Monthly Notices of the Royal Astronomical Society (2016)

On 19 Feb. 2016 nine Rosetta instruments serendipitously observed an outburst of gas and dust from the nucleus of comet 67P/Churyumov-Gerasimenko. Among these instruments were cameras and spectrometers ... [more ▼]

On 19 Feb. 2016 nine Rosetta instruments serendipitously observed an outburst of gas and dust from the nucleus of comet 67P/Churyumov-Gerasimenko. Among these instruments were cameras and spectrometers ranging from UV over visible to microwave wavelengths, in-situ gas, dust and plasma instruments, and one dust collector. At 9:40 a dust cloud developed at the edge of an image in the shadowed region of the nucleus. Over the next two hours the instruments recorded a signature of the outburst that significantly exceeded the background. The enhancement ranged from 50% of the neutral gas density at Rosetta to factors >100 of the brightness of the coma near the nucleus. Dust related phenomena (dust counts or brightness due to illuminated dust) showed the strongest enhancements (factors >10). However, even the electron density at Rosetta increased by a factor 3 and consequently the spacecraft potential changed from ˜-16 V to -20 V during the outburst. A clear sequence of events was observed at the distance of Rosetta (34 km from the nucleus): within 15 minutes the Star Tracker camera detected fast particles (˜25 m s[SUP]-1[/SUP]) while 100 μm radius particles were detected by the GIADA dust instrument ˜1 hour later at a speed of ~6 m s[SUP]-1[/SUP]. The slowest were individual mm to cm sized grains observed by the OSIRIS cameras. Although the outburst originated just outside the FOV of the instruments, the source region and the magnitude of the outburst could be determined. [less ▲]

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See detailThe dust environment of comet 67P/Churyumov-Gerasimenko from Rosetta OSIRIS and VLT observations in the 4.5 to 2.9 AU heliocentric distance range inbound
Moreno, F.; Snodgrass, C.; Hainaut, O. et al

in Astronomy and Astrophysics (2016), 587

Context. The ESA Rosetta spacecraft, currently orbiting around comet 67P/Churyumov-Gerasimenko, has already provided in situ measurements of the dust grain properties from several instruments,particularly ... [more ▼]

Context. The ESA Rosetta spacecraft, currently orbiting around comet 67P/Churyumov-Gerasimenko, has already provided in situ measurements of the dust grain properties from several instruments,particularly OSIRIS and GIADA. We propose adding value to those measurements by combining them with ground-based observations of the dust tail to monitor the overall, time-dependent dust-production rate and size distribution. <BR /> Aims: To constrain the dust grain properties, we take Rosetta OSIRIS and GIADA results into account, and combine OSIRIS data during the approach phase (from late April to early June 2014) with a large data set of ground-based images that were acquired with the ESO Very Large Telescope (VLT) from February to November 2014. <BR /> Methods: A Monte Carlo dust tail code, which has already been used to characterise the dust environments of several comets and active asteroids, has been applied to retrieve the dust parameters. Key properties of the grains (density, velocity, and size distribution) were obtained from Rosetta observations: these parameters were used as input of the code to considerably reduce the number of free parameters. In this way, the overall dust mass-loss rate and its dependence on the heliocentric distance could be obtained accurately. <BR /> Results: The dust parameters derived from the inner coma measurements by OSIRIS and GIADA and from distant imaging using VLT data are consistent, except for the power index of the size-distribution function, which is α = -3, instead of α = -2, for grains smaller than 1 mm. This is possibly linked to the presence of fluffy aggregates in the coma. The onset of cometary activity occurs at approximately 4.3 AU, with a dust production rate of 0.5 kg/s, increasing up to 15 kg/s at 2.9 AU. This implies a dust-to-gas mass ratio varying between 3.8 and 6.5 for the best-fit model when combined with water-production rates from the MIRO experiment. [less ▲]

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See detailConcurrent observations of ultraviolet aurora and energetic electron precipitation with Mars Express
Gérard, Jean-Claude ULg; Soret, Lauriane ULg; Libert, Ludivine ULg et al

in Journal of Geophysical Research. Space Physics (2015)

The database of the Spectroscopy for the Investigation of the Characteristics of the Atmosphere of Mars (SPICAM) instrument between late January 2004 and Mars 2014 has been searched to identify signatures ... [more ▼]

The database of the Spectroscopy for the Investigation of the Characteristics of the Atmosphere of Mars (SPICAM) instrument between late January 2004 and Mars 2014 has been searched to identify signatures of CO Cameron and CO<inf>2</inf>+ doublet ultraviolet auroral emissions. This study has almost doubled the number of auroral detections based on SPICAM spectra. Auroral emissions are located in the vicinity of the statistical boundary between open and closed field lines. From a total of 113 nightside orbits with SPICAM pointing to the nadir in the region of residual magnetic field, only nine nightside orbits show confirmed auroral signatures, some with multiple detections along the orbital track, leading to a total of 16 detections. The mean energy of the electron energy spectra measured during concurrent Analyzer of Space Plasma and Energetic Atoms/Electron Spectrometer observations ranges from 150 to 280eV. The ultraviolet aurora may be displaced poleward or equatorward of the region of enhanced downward electron energy flux by several tens of seconds and shows no proportionality with the electron flux at the spacecraft altitude. The absence of further UV auroral detection in regions located along crustal magnetic field structures where occasional aurora has been observed indicates that the Mars aurora is a time-dependent feature. These results are consistent with the scenario of acceleration of electrons by transient parallel electric field along semiopen magnetic field lines. © 2015. American Geophysical Union. All Rights Reserved. [less ▲]

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See detailDiurnal thermosphere scale height from MEX/SPICAM grazing limb data
Stiepen, Arnaud ULg; Gérard, Jean-Claude ULg; Bougher, S et al

Conference (2014, July 01)

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See detailVenus night side measurements of winds at 115 km altitude from NO bright patches tracking.
Bertaux, J.-L.; Gérard, Jean-Claude ULg; Stiepen, Arnaud ULg et al

Conference (2013, June)

N and O atoms produced by photo-dissociation of CO2 and N2 on the day side of Venus are transported to the night side in the thermospheric circulation. When the air parcel is descending, the recombination ... [more ▼]

N and O atoms produced by photo-dissociation of CO2 and N2 on the day side of Venus are transported to the night side in the thermospheric circulation. When the air parcel is descending, the recombination N+O→ NO produces the famous γ and δ bands of NO emission. Pioneer Venus (1978) suggested that the statistical center of the emission is off from the anti-solar point, about one- two hours in Local time after midnight. This is confirmed from SPICAV/VEX results, and the explanation generally accepted is the influence of retrograde super rotation. However, the emission takes place at 115 km, while VIRTIS/VEX, with maps of O2 emission (peak altitude 95 km) in the night side of Venus (recombination of O+O coming from the day side), has shown that the maximum of emission is statistically centered on the antisolar point. Therefore, there is no influence of super-rotation at 95 km. One way to explain this paradox is that the cause of the super rotation is different at 115 km and in the lower atmosphere. Alternately, some gravity waves could propagate from below, crossing the altitude 95 km with minimal interaction, and breaking around 115, depositing their momentum. Another consideration is that the altitude of N2 photo-dissociation is higher in the thermosphere than CO2, therefore the thermospheric circulation pattern may be different for the transport of N atoms, and O atoms. We have started building maps of the NO emission by moving around the spacecraft along its orbit on the night side. The idea is that NO emission is concentrated generally in rather well defined patches of light. Therefore, by comparing maps taken at 1 hour or 24 hr interval, we can make a “bright patch tracking”, and derive directly the velocity of the moving air parcel containing N and O (we are aware that a part of the motion could be due to a phase shift of a gravity wave, if it has some influence on the NO emission). Preliminary results from this exercise with Venus Express will be presented and discussed. [less ▲]

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See detailThe HARPS search for southern extra-solar planets: XXXI. The M-dwarf sample
Bonfils, X.; Delfosse, X.; Udry, S. et al

in Astronomy and Astrophysics (2013), 549

(Abridged) Searching for planets around stars with different masses probes the outcome of planetary formation for different initial conditions. This drives observations of a sample of 102 southern nearby ... [more ▼]

(Abridged) Searching for planets around stars with different masses probes the outcome of planetary formation for different initial conditions. This drives observations of a sample of 102 southern nearby M dwarfs, using a fraction of our guaranteed time on the ESO/HARPS spectrograph (Feb. 11th, 2003 to Apr. 1st 2009). This paper makes available the sample's time series, presents their precision and variability. We apply systematic searches and diagnostics to discriminate whether the observed Doppler shifts are caused by stellar surface inhomogeneities or by the radial pull of orbiting planets. We recover the planetary signals corresponding to 9 planets already announced by our group (Gl176b, Gl581b, c, d & e, Gl674b, Gl433b, Gl 667Cb and c). We present radial velocities that confirm GJ 849 hosts a Jupiter-mass planet, plus a long-term radial-velocity variation. We also present RVs that precise the planetary mass and period of Gl 832b. We detect long-term RV changes for Gl 367, Gl 680 and Gl 880 betraying yet unknown long-period companions. We identify candidate signals in the radial-velocity time series and demonstrate they are most probably caused by stellar surface inhomogeneities. Finally, we derive a first estimate of the occurrence of M-dwarf planets as a function of their minimum mass and orbital period. In particular, we find that giant planets (m sin i = 100-1,000 Mearth) have a low frequency (e.g. f<1% for P=1-10 d and f=0.02^{+0.03}_{-0.01} for P=10-100 d), whereas super-Earths (m sin i = 1-10 Mearth) are likely very abundant (f=0.36^{+0.25}_{-0.10} for P=1-10 d and f=0.35^{+0.45}_{-0.11} for P=10-100 d). We also obtained eta_earth=0.41^{+0.54}_{-0.13}, the frequency of habitable planets orbiting M dwarfs (1<m sin i<10 Mearth). For the first time, eta_earth is a direct measure and not a number extrapolated from the statistic of more massive and/or shorter-period planets. [less ▲]

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See detailSPICAM dayglow measurements: a tool to retrieve CO2 vertical density profile and exospheric temperatures
Stiepen, Arnaud ULg; Gérard, Jean-Claude ULg; Bougher, S. et al

Conference (2012, September)

We analyze the behavior of the CO2+ and CO Cameron ultraviolet dayglow in the atmosphere of Mars through a large dataset of dayside grazing limb observations performed by the Spectroscopy for ... [more ▼]

We analyze the behavior of the CO2+ and CO Cameron ultraviolet dayglow in the atmosphere of Mars through a large dataset of dayside grazing limb observations performed by the Spectroscopy for Investigation of Characteristics of the Atmosphere of Mars (SPICAM) on board the Mars Express spacecraft. Limb profiles are studied to retrieve the temperature of the Martian exosphere and its variability with season, latitude and solar activity. We use a one-dimensional chemical-diffusive model to retrieve the main features of the emissions and constrain the temperature and density vertical profiles of the main components of the Martian atmosphere. [less ▲]

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See detailA layer of ozone detected in the nightside upper atmosphere of Venus
Montmessin, Franck; Bertaux, J.-L.; Lefèvre, F. et al

in Icarus: International Journal of Solar System Studies (2011)

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See detailDiscovery and characterization of an ozone layer in Venus’atmosphere
Montmessin, F.; Bertaux, J.-L.; Lefèvre, F. et al

Conference (2011)

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See detailThe NO Venus nightglow: SPICAV observations and implications on transport in the lower thermosphere
Gérard, Jean-Claude ULg; Cox, Cédric ULg; Bertaux, J.-L.

Conference (2010, June 22)

A new set of 725 NO limb profiles has been analyzed. The profiles have been deconvolved and inverted to get volume emission rates. Updates mean VER peak altitude is 115 km, in excellent agreement with PV ... [more ▼]

A new set of 725 NO limb profiles has been analyzed. The profiles have been deconvolved and inverted to get volume emission rates. Updates mean VER peak altitude is 115 km, in excellent agreement with PV results obtained 30 years ago. The corresponding average vertical intensity is 1.2 kR. The altitude of emission occurs at a higher altitude near the bright spot region than at larger distances (by about 7 km). The location of the statistical bright spot is the same as observed with PV (that is shifted dawnward by 2 hrs and slightly south of AS point). The nightside mean vertical intensity is between 0.4 and 1.8 kR, which brackets the values derived from the limb profiles. These results, coupled with other airglow measurements, provide constraints on global atmospheric circulation and vertical transport [less ▲]

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See detailMars ultraviolet dayglow variability: SPICAM observations and comparison with airglow model
Cox, Cédric ULg; Gérard, Jean-Claude ULg; Hubert, Benoît ULg et al

in Journal of Geophysical Research. Planets (2010), 115

Dayglow ultraviolet emissions of the CO Cameron bands and the CO[SUB]2[/SUB][SUP]+[/SUP] doublet in the Martian atmosphere have been observed with the Spectroscopy for Investigation of Characteristics of ... [more ▼]

Dayglow ultraviolet emissions of the CO Cameron bands and the CO[SUB]2[/SUB][SUP]+[/SUP] doublet in the Martian atmosphere have been observed with the Spectroscopy for Investigation of Characteristics of the Atmosphere of Mars on board the Mars Express spacecraft. A large amount of limb profiles has been obtained which makes it possible to analyze variability of the brightness as well as of the altitude of the emission peak. Focusing on one specific season (Ls = [90,180] °), we find that the average CO peak brightness is equal to 118 ± 33 kR, with an average peak altitude of 121.1 ± 6.5 km. Similarly, the CO[SUB]2[/SUB][SUP]+[/SUP] emission shows a mean brightness of 21.6 ± 7.2 kR with a peak located at 119.1 ± 7.0 km. We show that the brightness intensity of the airglows is mainly controlled by the solar zenith angle and by solar activity. Moreover, during Martian summer of year 2005, an increase of the airglow peak altitude has been observed between Ls = 120° and 180°. We demonstrate that this variation is due to a change in the thermospheric local CO[SUB]2[/SUB] density, in agreement with observations performed by stellar occultation. Using a Monte Carlo one-dimensional model, we also show that the main features of the emission profiles can be reproduced for the considered set of data. However, we find it necessary to scale the calculated intensities by a fixed factor. [less ▲]

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See detailThe Mars ultraviolet dayglow variability: SPICAM observations and model comparison
Gérard, Jean-Claude ULg; Cox, Cédric ULg; Bougher, S. W. et al

Conference (2009, September 16)

Limb profiles of the CO Cameron and CO2+ doublet airglow have been observed over different conditions (latitude, season, SZA, F10.7). They have been individually modelled using currently accepted cross ... [more ▼]

Limb profiles of the CO Cameron and CO2+ doublet airglow have been observed over different conditions (latitude, season, SZA, F10.7). They have been individually modelled using currently accepted cross sections, and outputs from the MTGCM. They have been shown to co-vary, with a ICO/ICO2+ ratio of about 4.7, less than the modelled ratio.The peak brightness varies linearly with the F10.7 solar flux proxy, in a way compatible with the Mariner 6 and 7 observations. The intensity of both emissions is overestimated by the model (but large uncertainties exist in excitation cross sections). An increase of the altitude of both emissions has been observed during the 2005 summer season. It is a consequence of the dust load, followed by an increased thermospheric CO2 density observed with SPICAV during the same period. This density enhancement is partly predicted by GCM models. [less ▲]

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See detailConcurrent observations of the ultraviolet nitric oxide and infrared O[SUB]2[/SUB] nightglow emissions with Venus Express
Gérard, Jean-Claude ULg; Cox, Cédric ULg; Soret, Lauriane ULg et al

in Journal of Geophysical Research. Planets (2009), 114

Two prominent features of the Venus nightside airglow are the nitric oxide delta and gamma bands produced by radiative association of O and N atoms in the lower thermosphere and the O[SUB]2[/SUB] infrared ... [more ▼]

Two prominent features of the Venus nightside airglow are the nitric oxide delta and gamma bands produced by radiative association of O and N atoms in the lower thermosphere and the O[SUB]2[/SUB] infrared emission generated by three-body recombination of oxygen atoms in the upper mesosphere. The O[SUB]2[/SUB] airglow has been observed from the ground, during the Cassini flyby, and with VIRTIS on board Venus Express. It now appears that the global structure of the two emissions shows some similarities, but the statistical location of the region of strongest emission is not coincident. The Spectroscopy for Investigation of Characteristics of the Atmosphere of Venus (SPICAV) ultraviolet spectrograph has collected a large number of spectra of the Venus nitric oxide nightside airglow. Visible and Infrared Thermal Imaging Spectrometer (VIRTIS) images have been obtained at the limb and in the nadir-viewing mode and have provided new information on the horizontal and vertical distribution of the emission. We present the first concurrent observations of the two emissions observed with Venus Express. We show that nadir observations generally indicate a low degree of correlation between the two emissions observed quasi-simultaneously at a common location. A statistical study of limb profiles indicates that the altitude and the brightness of the two airglow layers generally do not covary. We suggest that this lack of correlation is explained by the presence of strong horizontal winds in the mesosphere-thermosphere transition region. They carry the downflowing atoms over large distances in such a way that regions of enhanced NO emission generally do not coincide with zones of bright O[SUB]2[/SUB] airglow. [less ▲]

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See detailVenus express: Highlights of the nominal mission
Titov, D. V.; Svedhem, H.; Taylor, F. W. et al

in Solar System Research (2009), 43

Venus Express is the first European (ESA) mission to the planet Venus. Its main science goal is to carry out a global survey of the atmosphere, the plasma environment, and the surface of Venus from orbit ... [more ▼]

Venus Express is the first European (ESA) mission to the planet Venus. Its main science goal is to carry out a global survey of the atmosphere, the plasma environment, and the surface of Venus from orbit. The payload consists of seven experiments. It includes a powerful suite of remote sensing imagers and spectrometers, instruments for in-situ investigation of the circumplanetary plasma and magnetic field, and a radio science experiment. The spacecraft, based on the Mars Express bus modified for the conditions at Venus, provides a versatile platform for nadir and limb observations as well as solar, stellar, and radio occultations. In April 2006 Venus Express was inserted in an elliptical polar orbit around Venus, with a pericentre height of Ë 250 km and apocentre distance of Ë 66000 km and an orbital period of 24 hours. The nominal mission lasted from June 4, 2006 till October 2, 2007, which corresponds to about two Venus sidereal days. Here we present an overview of the main results of the nominal mission, based on a set of papers recently published in Nature, Icarus, Planetary and Space Science, and Geophysical Research Letters. [less ▲]

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See detailThe HARPS search for southern extra-solar planets. XIV. Gl 176b, a super-Earth rather than a Neptune, and at a different period
Forveille, T.; Bonfils, X.; Delfosse, X. et al

in Astronomy and Astrophysics (2009), 493

A 10.24-day Neptune-mass planet was recently announced as orbiting the nearby M2 dwarf Gl 176, based on 28 radial velocities measured with the HRS spectrograph on the Hobby-Heberly Telescope. We obtained ... [more ▼]

A 10.24-day Neptune-mass planet was recently announced as orbiting the nearby M2 dwarf Gl 176, based on 28 radial velocities measured with the HRS spectrograph on the Hobby-Heberly Telescope. We obtained 57 radial velocities of Gl 176 with the ESO 3.6 m telescope and the HARPS spectrograph, which is known for its sub-m s[SUP]-1[/SUP] stability. The median photon-noise standard error of our measurements is 1.1 m s[SUP]-1[/SUP], significantly lower than the 4.7 m s[SUP]-1[/SUP] of the HET velocities, and the 4-year period over which they were obtained overlaps considerably with the epochs of the HET measurements. The HARPS measurements show no evidence of a signal at the period of the putative HET planet, suggesting that its detection was spurious. We do find, on the other hand, strong evidence of a lower mass 8.4 M_Earth planet, in a quasi-circular orbit and at the different period of 8.78 days. The host star has moderate magnetic activity and rotates on a 39-day period, which we confirm through modulation of both contemporaneous photometry and chromospheric indices. We detect that period, as well, in the radial velocities, but it is well removed from the orbital period and offers no cause for confusion. This new detection of a super-Earth (2 M_Earth < M sin (i) < 10 M_Earth) around an M dwarf adds to the growing evidence that such planets are common around very low-mass stars. A third of the 20 known planets with M sin (i)< 0.1 M_Jup and 3 of the 7 known planets with M sin (i) < 10 M_Earth orbit an M dwarf, in contrast to just 4 of the ~300 known Jupiter-mass planets. Based on observations made with the HARPS instrument on the ESO 3.6-m telescope at La Silla Observatory under program ID 072.C-0488. [less ▲]

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See detailThe HARPS search for southern extra-solar planets. X. A m sin i = 11 M_â planet around the nearby spotted M dwarf <ASTROBJ>GJ 674</ASTROBJ>
Bonfils, X.; Mayor, M.; Delfosse, X. et al

in Astronomy and Astrophysics (2007), 474

Context: How planet properties depend on stellar mass is a key diagnostic of planetary formation mechanisms. Aims: This motivates planet searches around stars that are significantly more massive or less ... [more ▼]

Context: How planet properties depend on stellar mass is a key diagnostic of planetary formation mechanisms. Aims: This motivates planet searches around stars that are significantly more massive or less massive than the Sun, and in particular our radial velocity search for planets around very low-mass stars. Methods: As part of that program, we obtained measurements of <ASTROBJ>GJ 674</ASTROBJ>, an M 2.5 dwarf at d = 4.5 pc. These measurements have dispersion much in excess of their internal errors. An intensive observing campaign demonstrates that the excess dispersion is due to two superimposed coherent signals, with periods of 4.69 and 35 days. Results: These data are described well by a 2-planet Keplerian model where each planet has a ~11 M_â minimum mass. A careful analysis of the (low-level) magnetic activity of <ASTROBJ>GJ 674</ASTROBJ>, however, demonstrates that the 35-day period coincides with the stellar rotation period. This signal therefore originates in a spot inhomogeneity modulated by stellar rotation. The 4.69-day signal, on the other hand, is caused by a bona-fide planet, <ASTROBJ>GJ 674b</ASTROBJ>. Conclusions: Its detection adds to the growing number of Neptune-mass planets around M-dwarfs and reinforces the emerging conclusion that this mass domain is much more populated than the Jovian mass range. We discuss the metallicity distributions of M dwarf with and without planets and find a low 11% probability that they are drawn from the same parent distribution. Moreover, we find tentative evidence that the host star metallicity correlates with the total mass of their planetary system. Based on observations made with the HARPS instrument on the ESO 3.6 m telescope under the GTO program ID 072.C-0488 at Cerro La Silla (Chile). Radial-velocity, photometric and Ca II H+K index time series are only available in electronic format the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strabg.fr/cgi-bin/qcat?J/A+A/474/293 [less ▲]

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See detailThe NO Martian Nightglow observed with the SPICAM UV Spectrometer and comparison with a one-dimensional model.
Cox, Cédric ULg; Saglam, A.; Gérard, Jean-Claude ULg et al

Conference (2007, April)

Observations in the 108-317 nm wavelength range have been performed with the SPICAM ultraviolet spectrometer aboard the Mars Express (MEX) mission. SPICAM has observed the ultraviolet nightglow emission ... [more ▼]

Observations in the 108-317 nm wavelength range have been performed with the SPICAM ultraviolet spectrometer aboard the Mars Express (MEX) mission. SPICAM has observed the ultraviolet nightglow emission in the δ (190-240 nm) and γ (225-270 nm) bands of nitric oxide (Bertaux et al. 2005). This emission arises from the recombination between O(3P) and N(4S) atoms that are produced on the day side to form NO in the night side. We present a summary of the night limb observations performed during the MEX mission. In particular, we describe the variability of the brightness and peak altitude. We find that the altitude of maximum emission varies between 55 and 90 km and the brightness is in the range 0.2 to 4.5 kR. We compare these observations with the results of a chemical-diffusive atmospheric model which solves the continuity equation for O, N(4S) and NO continuity equation using the finite volume method on one dimensional grid. The eddy coefficient, whose value is very uncertain, is a free parameter adjusted to match the observational data. [less ▲]

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