References of "Stiepen, Arnaud"
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See detailFirst Detection of the Nitric Oxide Dayglow on Mars
Stevens, Michael H.; Siskind, David E.; Evans, J. Scott et al

Conference (2017, October 01)

Nitric oxide (NO) is a well-known indicator of solar and auroral activity in the terrestrial upper atmosphere. Direct measurements of NO on Mars can therefore constrain studies of energetic processes ... [more ▼]

Nitric oxide (NO) is a well-known indicator of solar and auroral activity in the terrestrial upper atmosphere. Direct measurements of NO on Mars can therefore constrain studies of energetic processes controlling the composition and structure of its upper atmosphere (80-200 km). Identifying and quantifying these processes is one of the science objectives of NASA’s Mars Atmosphere and Volatile Evolution (MAVEN) mission currently orbiting Mars. NO can be observed directly by solar resonance fluorescence in the mid-ultraviolet (MUV). Indeed, this approach has routinely been used to measure terrestrial NO for 50 years. On Mars, this “dayglow” emission is very weak relative to other bright MUV features and thus has confounded attempts at its detection there for nearly the same amount of time. Here, we report the first detection of the NO dayglow in the Martian atmosphere using limb observations by the Imaging Ultraviolet Spectrograph (IUVS) on the MAVEN spacecraft. The detection is enabled by the spectral modeling and removal of the carbon monoxide Cameron bands, which dominate the MUV limb spectra. We focus on the spectral region between 213.0-225.5 nm, where three NO gamma bands emit. We will infer NO densities from the dayglow spectra and compare our observations with predictions from a photochemical model. We will discuss the implications, particularly in the context of previous in situ measurements. [less ▲]

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See detailMars topographic clouds: MAVEN/IUVS observations and LMD MGCM predictions
Schneider, Nicholas M.; Connour, Kyle; Forget, Francois et al

Conference (2017, October 01)

The Imaging Ultraviolet Spectrograph (IUVS) instrument on the Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft takes mid-UV spectral images of the Martian atmosphere. From these apoapse disk ... [more ▼]

The Imaging Ultraviolet Spectrograph (IUVS) instrument on the Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft takes mid-UV spectral images of the Martian atmosphere. From these apoapse disk images, information about clouds and aerosols can be retrieved and comprise the only MAVEN observations of topographic clouds and cloud morphologies. Measuring local time variability of large-scale recurring cloud features is made possible with MAVEN’s ~4.5-hour elliptical orbit, something not possible with sun-synchronous orbits. We have run the LMD MGCM (Mars global circulation model) at 1° x 1° resolution to simulate water ice cloud formation with inputs consistent with observing parameters and Mars seasons. Topographic clouds are observed to form daily during the late mornings of northern hemisphere spring and this phenomenon recurs until late summer (Ls = 160°), after which topographic clouds wane in thickness. By northern fall, most topographic clouds cease to form except over Arsia Mons and Pavonis Mons, where clouds can still be observed. Our data show moderate cloud formation over these regions as late as Ls = 220°, something difficult for the model to replicate. Previous studies have shown that models have trouble simulating equatorial cloud thickness in combination with a realistic amount of water vapor and not-too-thick polar water ice clouds, implying aspects of the water cycle are not fully understood. We present data/model comparisons as well as further refinements on parameter inputs based on IUVS observations. [less ▲]

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See detailFirst Retrieval of Thermospheric Carbon Monoxide From Mars Dayglow Observations
Evans, J. Scott; Stevens, Michael H.; Jain, Sonal et al

Conference (2017, October 01)

As a minor species in the Martian thermosphere, Carbon Monoxide (CO) is a tracer that can be used to constrain changing circulation patterns between the lower thermosphere and upper mesosphere of Mars. By ... [more ▼]

As a minor species in the Martian thermosphere, Carbon Monoxide (CO) is a tracer that can be used to constrain changing circulation patterns between the lower thermosphere and upper mesosphere of Mars. By linking CO density distributions to dynamical wind patterns, the structure and variability of the atmosphere will be better understood. Direct measurements of CO can therefore provide insight into the magnitude and pattern of winds and provide a metric for studying the response of the atmosphere to solar forcing. In addition, CO measurements can help solve outstanding photochemical modeling problems in explaining the abundance of CO at Mars. CO is directly observable by electron impact excitation and solar resonance fluorescence emissions in the far-ultraviolet (FUV). The retrieval of CO from solar fluorescence was first proposed over 40 years ago, but has been elusive at Mars due to significant spectral blending. However, by simulating the spectral shape of each contributing emission feature, electron impact excitation and solar fluorescence brightnesses can be extracted from the composite spectrum using a multiple linear regression approach. We use CO Fourth Positive Group (4PG) molecular band emission observed on the limb (130 - 200 km) by the Imaging Ultraviolet Spectrograph (IUVS) on NASA’s Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft over both northern and southern hemispheres from October 2014 to December 2016. We present the first direct retrieval of CO densities by FUV remote sensing in the upper atmosphere of Mars. Atmospheric composition is inferred using the terrestrial Atmospheric Ultraviolet Radiance Integrated Code adapted to the Martian atmosphere. We investigate the sensitivity of CO density retrievals to variability in solar irradiance, solar longitude, and local time. We compare our results to predictions from the Mars Global Ionosphere-Thermosphere Model as well as in situ measurements by the Neutral Gas and Ion Mass Spectrometer on MAVEN and quantify any differences. [less ▲]

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See detailMars’ seasonal mesospheric transport seen through nitric oxide nightglow
Milby, Zachariah; Stiepen, Arnaud ULiege; Jain, Sonal et al

Conference (2017, October 01)

We analyze the ultraviolet nightglow in the atmosphere of Mars through nitric oxide (NO) δ and γ band emissions as observed by the Imaging UltraViolet Spectrograph (IUVS) instrument onboard the Mars ... [more ▼]

We analyze the ultraviolet nightglow in the atmosphere of Mars through nitric oxide (NO) δ and γ band emissions as observed by the Imaging UltraViolet Spectrograph (IUVS) instrument onboard the Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft when it is at apoapse and periapse.In the dayside thermosphere of Mars, solar extreme-ultraviolet radiation dissociates CO[SUB]2[/SUB] and N[SUB]2[/SUB] molecules. O([SUP]3[/SUP]P) and N([SUP]4[/SUP]S) atoms are carried from the dayside to the nightside by the day-night hemispheric transport process, where they descend through the nightside mesosphere and can radiatively recombine to form NO(C[SUP]2[/SUP]Π). The excited molecules rapidly relax by emitting photons in the UV δ and γ bands. These emissions are indicators of the N and O atom fluxes from the dayside to Mars’ nightside and the descending circulation pattern from the nightside thermosphere to the mesosphere (e.g. Bertaux et al., 2005 ; Bougher et al., 1990 ; Cox et al., 2008 ; Gagné et al., 2013 ; Gérard et al., 2008 ; Stiepen et al., 2015, 2017).Observations of these emissions are gathered from a large dataset spanning different seasonal conditions.We present discussion on the variability in the brightness and altitude of the emission with season, geographical position (longitude), and local time, along with possible interpretation by local and global changes in the mesosphere dynamics. We show the possible impact of atmospheric waves forcing longitudinal variability and data-to-model comparisons indicating a wave-3 structure in Mars’ nightside mesosphere. Quantitative comparison with calculations of the Laboratoire de Météorologie Dynamique-Mars Global Climate Model (LMD-MGCM) suggests the model reproduces both the global trend of NO nightglow emission and its seasonal variation. However, it also indicates large discrepancies, with the emission up to a factor 50 times fainter in the model, suggesting that the predicted transport is too efficient toward the night winter pole in the thermosphere by ˜20° latitude to the north.These questions are now addressed through an extensive dataset of disk images, in complement to improved simulations of the LMD-MGCM and the Mars Global Ionosphere-Thermosphere Model (MGITM) models. [less ▲]

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See detailUnveiling Mars nightside mesosphere dynamics by IUVS/MAVEN global images of NO nightglow
Stiepen, Arnaud ULiege; Jain, S. K.; Schneider, N. M. et al

Conference (2017, September 01)

We analyze the morphology of the ultraviolet nightglow in the Martian upper atmosphere through Nitric Oxide (NO) δ and γ bands emissions observed by the Imaging Ultraviolet Spectrograph instrument on the ... [more ▼]

We analyze the morphology of the ultraviolet nightglow in the Martian upper atmosphere through Nitric Oxide (NO) δ and γ bands emissions observed by the Imaging Ultraviolet Spectrograph instrument on the Mars Atmosphere and Volatile EvolutioN spacecraft. The seasonal dynamics of the Martian thermosphere-mesosphere can be constrained based on the distribution of these emissions. We show evidence for local (emission streaks and splotches) and global (longitudinal and seasonal) variability in brightness of the emission and provide quantitative comparisons to GCM simulations. [less ▲]

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See detailMAVEN IUVS Observations of the Aftermath of the Comet Siding Spring Meteor Shower on Mars
Schneider, N. M.; Crismani, M.; Deighan, J. I. et al

Conference (2017, September 01)

A comet's close passage by Mars deposited an unprecedented amount of vaporized dust whose elements were detected by the MAVEN spacecraft.

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See detailHydrogen Loss from Mars: Seasonal and Sourced from Upper Atmospheric Water
Chaffin; Deighan; Stewart et al

Conference (2017, August 09)

Mars has lost a significant fraction of its initial water inventory to space over its history. This loss proceeds via a chemical chain initiated in the lower and middle atmosphere below 100 km altitude ... [more ▼]

Mars has lost a significant fraction of its initial water inventory to space over its history. This loss proceeds via a chemical chain initiated in the lower and middle atmosphere below 100 km altitude, which results in H escape to space in the collisionless corona above about 200 km altitude. Hydrogen loss from Mars is tracked via brigtness measurements of this corona in Lyman alpha light at 121.6 nm, which is scattered by neutral H orbiting and escaping the planet. Here we present observations of H escape variability made by the Mars Atmosphere and Volatile EvolutioN (MAVEN) mission's Imaging Ultraviolet Spectrograph (IUVS) that demonstrate the seasonal dependence of H escape, adding to evidence initially gathered by Mars Express and the Hubble Space Telescope. We show that for two Mars years the atmosphere has exhibited enhanced H escape in Southern Summer near perihelion. We also present the result of photochemical model calculations which demonstrate that this variation can be explained as a result of high concentrations of water vapor in the upper atmosphere, consistent with Mars Express solar occultation measurements and several general circulation models. Our results demonstrate that the large variations in H escape at high altitudes can be driven by lower atmospheric dynamics, suggesting that Mars hydrogen escape may depend on climate, in addition to the long-term evolution of Martian climate depending on atmospheric escape. [less ▲]

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See detailState of Martian Upper Atmosphere as Observed by Imaging Ultraviolet Spectroscope Onboard MAVEN
Jain; Stewart; Deighan et al

Conference (2017, August 09)

NASA’s MAVEN spacecraft has taken more than two earth years (one Martian year) of observations of Mars to understand the process of Martian atmospheric evolution. The Imaging Ultraviolet Spectrograph ... [more ▼]

NASA’s MAVEN spacecraft has taken more than two earth years (one Martian year) of observations of Mars to understand the process of Martian atmospheric evolution. The Imaging Ultraviolet Spectrograph (IUVS) on board MAVEN observes Mars in far and mid ultraviolet (110-340 nm) with unique scanning and pointing capabilities, which are optimized for airglow studies. Dayglow emissions observed on Mars are a perfect tracer for the processes occurring in the emitting region of the atmosphere (100-200 km) and provide basic information about atmospheric composition (and its structure), and give insight into the dynamics, energetics, and physics and chemistry of the thermosphere. With its wide spatial and temporal coverage, IUVS observations of Martian dayglow has contributed immensely to our understanding of the Martian upper atmosphere and its response to incoming solar flux (EUV/FUV) and coupling between lower and upper atmosphere through tides and waves. In this presentation, I will talk about an overview of scientific results obtained by IUVS dayglow measurements, including (1) spatial/temporal distribution of major MUV and FUV emissions and their seasonal variability; (2) the seasonal variation of thermosphere temperatures inferred from dayglow measurements; (3) the effect of solar EUV flux (including the ~27-day solar rotation) and heliocentric distance on upper atmosphere temperature structure. We will present an overview of these results and a discussion of their implications for the state of the Martian upper atmosphere. [less ▲]

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See detailMAVEN/IUVS Observations of the Reflectance Spectrum of Phobos
Chaffin; Deighan; Schneider et al

Conference (2017, August 08)

The Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft occasionally has close encounter seasons with Phobos as a consequence of its orbital precession and its apoapsis being near the orbit of the ... [more ▼]

The Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft occasionally has close encounter seasons with Phobos as a consequence of its orbital precession and its apoapsis being near the orbit of the moon. During one encounter season in late 2015, MAVEN's Imaging Ultraviolet Spectrograph (IUVS) was able to gather the first ever spectral images of the moon in the mid-ultraviolet. During these flybys, IUVS was able to observe the trailing hemisphere of the moon, producing spectra useful for comparison with the Mariner 9 Ultraviolet Spectrometer measurements, which observed only the moon's leading side. The IUVS data reveal that the trailing side of the Moon is bluer than the leading side, indicating possible differences in the weathering history of the hemispheres. In addition, we see some evidence for an absorption feature longward of 300 nm, potentially produced by organic compounds, in accordance with Mariner 9 and SPICAM/UV observations. We will present an overview of our images and spectra and a discussion of their interpretation for the history and formation of Phobos. [less ▲]

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See detailScience Highlights from MAVEN/IUVS After Two Years in Mars Orbit
Jain; Schneider; Stiepen, Arnaud ULiege et al

Conference (2017, August 08)

The Mars Atmosphere and Volatile EvolutioN (MAVEN) mission's Imaging Ultraviolet Spectrograph (IUVS) observes Mars in the far and mid ultraviolet (110-340 nm), investigating lower and upper atmospheric ... [more ▼]

The Mars Atmosphere and Volatile EvolutioN (MAVEN) mission's Imaging Ultraviolet Spectrograph (IUVS) observes Mars in the far and mid ultraviolet (110-340 nm), investigating lower and upper atmospheric structure and indirectly probing neutral atmospheric escape. The instrument is among the most powerful spectrographs sent to another planet, with several key capabilities: separate Far-UV & Mid-UV channels for stray light control; a high-resolution echelle mode to resolve deuterium and hydrogen emission; internal instrument pointing and scanning capabilities to allow complete mapping and nearly continuous operation; and optimization for airglow studies. After two Earth years in orbit (one Mars year), IUVS has assembled a large quantity of data and provided insights on present-day processes at Mars including dayglow, nightglow, aurora, meteor showers, clouds, and solar-planetary interactions. In this presentation, we will highlight several new discoveries made by IUVS. Among the key results obtained by IUVS are: (1) discovery of the widespread occurrence of a diffuse proton aurora representing a previously unknown source of energy deposition into the atmospheres of unmagnetized planets; (2) first spatial mapping of nitric oxide nightglow reveals regions of atmospheric downwelling necessitating substantial changes to global atmospheric circulation models; (3) a new high-spatial-resolution UV imaging mode allows detection of clouds from nadir to limb and their local time evolution, as well as unprecedented determinations of Mars’ low-altitude ozone; (4) discovery of a persistent meteoric metal layer in Martian atmosphere; (5) atmospheric structure, composition and dynamics from stellar occultation. We will present an overview of these results and a discussion of their implications for characterizing the state of the atmosphere and its evolution. [less ▲]

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See detailSeasonal Transport in Mars’ Mesosphere revealed by Nitric Oxide Nightglow
Stiepen, Arnaud ULiege

Conference (2017, June 21)

We analyze the ultraviolet nightglow in the atmosphere of Mars through Nitric Oxide (NO) δ and γ bands emissions. On the dayside thermosphere of Mars, solar extreme ultraviolet radiation partly ... [more ▼]

We analyze the ultraviolet nightglow in the atmosphere of Mars through Nitric Oxide (NO) δ and γ bands emissions. On the dayside thermosphere of Mars, solar extreme ultraviolet radiation partly dissociates CO2 and N2 molecules. O(3P) and N(4S) atoms are carried by the day-to-night hemispheric transport. They preferentially descend in the nightside mesosphere in the winter hemisphere, where they can radiatively recombine to form NO(C2Π). The excited molecules promptly relax by emitting photons in the UV δ bands and in the γ bands through cascades via the A2Σ, v’ = 0 state. These emissions are thus indicators of the N and O atom fluxes transported from the dayside to Mars’ nightside and the winter descending circulation pattern from the nightside thermosphere to the mesosphere (e.g. Bertaux et al., 2005 ; Bougher et al., 1990 ; Cox et al., 2008 ; Gagné et al., 2013 ; Gérard et al., 2008 ; Stiepen et al., 2015, 2017). Observations of these emissions have been accumulated on a large dataset of nightside disk images and vertical profiles obtained at the limb by the Imaging Ultraviolet Spectrograph (IUVS, McClintock et al., 2015) instrument when the Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft is at its apoapsis and its periapsis phases along its orbit, respectively. We present discussion on the variability in the brightness and altitude and of the emission with season, geographical position and local time and possible interpretation for local and global changes in the mesosphere dynamics. IUVS images and limb scans reveal unexpected complex structure of the emission. The brightest emission is observed close to the winter pole. The emission is also surprisingly more intense in some longitude, revealing possible impact of tides and waves in Mars’ nightside mesosphere. Observations also reveal spots and streaks, indicating irregularities in the wind circulation pattern. The disk images and limb profiles are compared to the LMD-MGCM model (Gonzàlez-Galindo et al., 2009 ; Lopez-Valverde et al., 2011) to focus on the seasonal, local time and geographical influences on the NO Nightglow emission. We will also provide a statistical study of the regions of enhanced brightness (i.e. splotches and streaks) and discuss possible interpretation from the comparison to the GCM. [less ▲]

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See detailMartian mesospheric cloud observations by IUVS on MAVEN: Thermal tides coupled to the upper atmosphere
Stevens; Siskind; Evans et al

in Geophysical Research Letters (2017), 44

The manuscript describes the observation of Martian mesosphericclouds between 60 and 80 km altitude by the Imaging Ultraviolet Spectrograph (IUVS) on NASA’sMAVEN spacecraft. The cloud observations are ... [more ▼]

The manuscript describes the observation of Martian mesosphericclouds between 60 and 80 km altitude by the Imaging Ultraviolet Spectrograph (IUVS) on NASA’sMAVEN spacecraft. The cloud observations are uniquely obtained at early morning local times, whichcomplement previous observations obtained primarily later in the diurnal cycle. Differences in thegeographic distribution of the clouds from IUVS observations indicate that the local time is crucial for theinterpretation of mesospheric cloud formation. We also report concurrent observations of upperatmospheric scale heights near 170 km altitude, which are diagnostic of temperature. These observationssuggest that the dynamics enabling the formation of mesospheric clouds propagate all the way to theupper atmosphere. [less ▲]

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See detailHighlights from two years of remote sensing at Mars with MAVEN’s Imaging Ultraviolet Spectrograph
Chaffin; Schneider; Deighan et al

Poster (2017, April 27)

The Mars Atmosphere and Volatile EvolutioN (MAVEN) mission’s Imaging Ultraviolet Spectrograph (IUVS) observes Mars in the far and mid ultraviolet (110-340 nm), investigating lower and upper atmospheric ... [more ▼]

The Mars Atmosphere and Volatile EvolutioN (MAVEN) mission’s Imaging Ultraviolet Spectrograph (IUVS) observes Mars in the far and mid ultraviolet (110-340 nm), investigating lower and upper atmospheric structure and indirectly probing neutral atmospheric escape. After two Earth years in orbit (one Mars year), IUVS has assembled a large quantity of data and made many discoveries, some of which we report here. Among the key results obtained by IUVS are: (1) discovery of the widespread occurrence of a diffuse proton aurora, representing a newly discovered means of energy deposition into the atmospheres of unmagnetized planets; (2) continued investigation of time-variability in H and O escape, which have dessicated the planet over its history; and (3) synoptic characterization of thermospheric variability and response to solar input. We will present an overview of these results and a discussion of their implications for the state of the atmosphere and its evolution. [less ▲]

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See detailObjectif Mars
Stiepen, Arnaud ULiege

Conference given outside the academic context (2017)

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See detailEmbarquement pour Mars: défi et opportunité
Stiepen, Arnaud ULiege

Conference given outside the academic context (2017)

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See detailEmbarquement pour Mars
Stiepen, Arnaud ULiege

Conference given outside the academic context (2017)

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See detailObjectif Mars: défi ou utopie?
Stiepen, Arnaud ULiege

Conference given outside the academic context (2017)

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See detailMars Ozone mapping with MAVEN IUVS
Lefèvre; Stiepen, Arnaud ULiege; IUVS team

Conference (2017, January 20)

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See detailCharacterization of High Altitude Clouds at the Martian Limb and Terminator Using MAVEN IUVS Observations
Deighan; Stiepen, Arnaud ULiege; IUVS team

Conference (2017, January 20)

Detailed reference viewed: 10 (0 ULiège)
See detailA persistent meteoric layer in Mars' atmosphere
Crismani; Schneider; Plane et al

Poster (2017, January 18)

Detailed reference viewed: 13 (0 ULiège)