References of "Stiepen, Arnaud"
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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 ▲]

Detailed reference viewed: 17 (0 ULg)
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 ▲]

Detailed reference viewed: 13 (0 ULg)
See detailScience Highlights from MAVEN/IUVS After Two Years in Mars Orbit
Jain; Schneider; Stiepen, Arnaud ULg 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 ▲]

Detailed reference viewed: 43 (0 ULg)
See detailSeasonal Transport in Mars’ Mesosphere revealed by Nitric Oxide Nightglow
Stiepen, Arnaud ULg

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 ▲]

Detailed reference viewed: 18 (1 ULg)
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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 ▲]

Detailed reference viewed: 18 (3 ULg)
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 ▲]

Detailed reference viewed: 16 (1 ULg)
See detailObjectif Mars
Stiepen, Arnaud ULg

Conference given outside the academic context (2017)

Detailed reference viewed: 18 (0 ULg)
See detailEmbarquement pour Mars: défi et opportunité
Stiepen, Arnaud ULg

Conference given outside the academic context (2017)

Detailed reference viewed: 15 (1 ULg)
See detailEmbarquement pour Mars
Stiepen, Arnaud ULg

Conference given outside the academic context (2017)

Detailed reference viewed: 27 (4 ULg)
See detailObjectif Mars: défi ou utopie?
Stiepen, Arnaud ULg

Conference given outside the academic context (2017)

Detailed reference viewed: 19 (1 ULg)
See detailMars Ozone mapping with MAVEN IUVS
Lefèvre; Stiepen, Arnaud ULg; IUVS team

Conference (2017, January 20)

Detailed reference viewed: 15 (1 ULg)
See detailCharacterization of High Altitude Clouds at the Martian Limb and Terminator Using MAVEN IUVS Observations
Deighan; Stiepen, Arnaud ULg; IUVS team

Conference (2017, January 20)

Detailed reference viewed: 10 (1 ULg)
See detailGlobal Simulation of UV atmospheric Emissions
Gonzalez-Galindo; Lopez-Valverde; Forget et al

Poster (2017, January 19)

Detailed reference viewed: 16 (2 ULg)
See detailA persistent meteoric layer in Mars' atmosphere
Crismani; Schneider; Plane et al

Poster (2017, January 18)

Detailed reference viewed: 15 (0 ULg)
See detailThree Types of Aurora observed by MAVEN/IUVS: Implications for Mars’ upper Atmosphere Energy Budget
Connour; Schneider; Jain et al

Poster (2017, January 17)

Detailed reference viewed: 36 (4 ULg)
See detailGlobal UV Imaging by MAVEN/IUVS: Diurnal Cloud Formation, Dust Storms and Atmospheric Scattering.
Schneider; Deighan; Jain et al

Conference (2017, January 17)

Detailed reference viewed: 15 (1 ULg)
See detailNO Nightglow studies status
Stiepen, Arnaud ULg; Jain; Deighan et al

Conference (2017, January 16)

Detailed reference viewed: 11 (1 ULg)
See detailEmbarquement pour Mars
Stiepen, Arnaud ULg

Conference given outside the academic context (2017)

Detailed reference viewed: 11 (1 ULg)