References of "Crismani, M"
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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 detailMAVEN IUVS Remote Sensing Highlights Relevant to Upcoming TGO Observations
Chaffin, M.; Schneider, N. M.; Deighan, J. et al

in From Mars Express to ExoMars (2018, February 01)

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See detailThree types of aurora on Mars
Schneider, N.; Jain, S.; Deighan, J. et al

Conference (2017, December)

Observations by the Imaging UltraViolet Spectrograph (IUVS) on the MAVEN spacecraft have identified three types of aurora on Mars, each profoundly different from comparable types on Earth and other ... [more ▼]

Observations by the Imaging UltraViolet Spectrograph (IUVS) on the MAVEN spacecraft have identified three types of aurora on Mars, each profoundly different from comparable types on Earth and other planets. The primary reason for these differences is Mars’ lack of a global magnetic field and presence of localized crustral magnetic fields primarily in the southern hemisphere. IUVS is MAVEN’s remote sensing instrument for study of the Mars atmosphere. The instrument records spatially-resolved spectra in the far-UV (110-190 nm) and Mid-UV (180-340 nm). By virtue of an internal scan mirror and a gimbaled instrument platform, IUVS obtains useful spectra on Mars with >50% duty cycle, including Mars’ nightside. IUVS performs limb scans during the spacecraft periapse, and obtains UV images of the planet from reconstructed apoapse disk scans. Two types of aurora have been detected on Mars’ nightside by virtue of emissions requiring excitation by precipitating charged particles. The first type, discrete aurora, are localized near the boundary between open and closed crustal magnetic field lines. They generally appear at ~140 km altitude and the spectra correspond to moderate mean electron energy precipitation. These detections confirm the discovery of discrete discovered by Mars Express/SPICAM. IUVS has discovered a second type, diffuse aurora, which are widespread and potentially global. They occur as low as 70 km altitude; the spectra, depth of penetration and timing are consistent with the precipitation of relativistic electrons from the Sun. IUVS has discovered a third type, proton aurora, on Mars’ dayside as excess hydrogen Lyman alpha emission confined to Mars’ thermosphere. The intermittent excesses appear correlated with enhanced solar wind conditions. This type is the most common form of aurora detected by IUVS. IUVS results dispel a common misconception that aurora only occur near the edges of closed planetary magnetic field lines. While this is true for terrestrial aurora and discrete aurora on Mars, it is false for Mars’ diffuse and proton auroras. In this sense, Mars serves as the best archetype for auroral processes on unmagnetized planets in our solar system and beyond. [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 detailVariability of D and H in the Martian Upper Atmosphere Observed with the MAVEN IUVS Echelle Channel
Clarke, J. T.; Mayyasi, M.; Bhattacharyya, D. et al

in Journal of Geophysical Research. Space Physics (2017)

The MAVEN IUVS instrument contains an echelle spectrograph channel designed to measure D and H Ly α emissions from the upper atmosphere of Mars. This channel has successfully recorded both emissions ... [more ▼]

The MAVEN IUVS instrument contains an echelle spectrograph channel designed to measure D and H Ly α emissions from the upper atmosphere of Mars. This channel has successfully recorded both emissions, which are produced by resonant scattering of solar emission, over the course of most of a martian year. The fundamental purpose of these measurements is to understand the physical principles underlying the escape of H and D from the upper atmosphere into space, and thereby to relate present-day measurements of an enhanced HDO/H2O ratio in the bulk atmosphere to the water escape history of Mars. Variations in these emissions independent of the solar flux reflect changes in the density and/or temperature of the species in the upper atmosphere. The MAVEN measurements show that the densities of both H and D vary by an order of magnitude over a martian year, and not always in synch with each other. This discovery has relevance to the processes by which H and D escape into space. One needs to understand the controlling factors to be able to extrapolate back in time to determine the water escape history from Mars at times when the atmosphere was thicker, when the solar flux and solar wind were stronger, etc. Further measurements will be able to identify the specific controlling factors for the large changes in H and D, which likely result in large changes in the escape fluxes of both species. [less ▲]

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See detailTwo Types of Aurora on Mars as Observed by MAVEN's Imaging UltraViolet Spectrograph
Schneider, Nicholas M.; Deighan, J.; Jain, S. K. et al

in AAS/Division for Planetary Sciences Meeting Abstracts (2015, November 01)

The Imaging UltraViolet Spectrograph (IUVS) on the MAVEN spacecraft has detected two distinct types of auroral emission on Mars. First, we report the discovery of a low altitude, diffuse aurora spanning ... [more ▼]

The Imaging UltraViolet Spectrograph (IUVS) on the MAVEN spacecraft has detected two distinct types of auroral emission on Mars. First, we report the discovery of a low altitude, diffuse aurora spanning much of Mars’ northern hemisphere coincident with a solar energetic particle outburst. IUVS observed northerly latitudes during late December 2014, detecting auroral emission in virtually all nightside observations for ~5 days spanning virtually all geographic longitudes. The vertical profile showed emission down to ~70 km altitude (1 microbar), deeper than confirmed at any other planet. The onset and duration of emission coincide with the observed arrival of solar energetic particles up to 200 keV precipitating directly and deeply into the atmosphere. Preliminary modeling of the precipitation, energy deposition and spectral line emission yields good matches to the observations. These observations represent a new class of planetary auroras produced in the Martian middle atmosphere. Given minimal magnetic fields over most of the planet, Mars is likely to exhibit aurora more globally than Earth.Second, we confirm the existence of small patches of discrete aurora near crustal magnetic fields in Mars' southern hemisphere, as observed previously by SPICAM on Mars Express (Bertaux et al., Nature, 435, 790-794 (2005)). IUVS observed southern latitudes in July and August 2015, detecting discrete auroral emission in ~1% of suitable observations. Limb scans resolved both vertically and along-slit indicate this type of auroral emission was patchy on the scale of ~40 km, and located at higher altitudes ~140 km. The higher altitudes imply a lower energy of precipitating particles. The mix of spectral emissions also differed signficiantly from the diffuse aurora, indicating different excitation and quenching processes.We will discuss the observed properties of the aurora and associated charged particle precipitation, as well as the broader implications of this high-energy deposition into Mars' atmopshere. [less ▲]

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See detailDiscovery of diffuse aurora on Mars
Schneider, N. M.; Deighan, J. I.; Jain, S. K. et al

in Science (2015), 350(6261),

Planetary auroras reveal the complex interplay between an atmosphere and the surrounding plasma environment.We report the discovery of low-Altitude, diffuse auroras spanning much of Mars' northern ... [more ▼]

Planetary auroras reveal the complex interplay between an atmosphere and the surrounding plasma environment.We report the discovery of low-Altitude, diffuse auroras spanning much of Mars' northern hemisphere, coincident with a solar energetic particle outburst. The Imaging Ultraviolet Spectrograph, a remote sensing instrument on the Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft, detected auroral emission in virtually all nightside observations for ~5 days, spanning nearly all geographic longitudes. Emission extended down to ~60 kilometer (km) altitude (1 microbar), deeper than confirmed at any other planet. Solar energetic particles were observed up to 200 kilo-electron volts; these particles are capable of penetrating down to the 60 km altitude. Given minimal magnetic fields over most of the planet, Mars is likely to exhibit auroras more globally than Earth. [less ▲]

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See detailMAVEN observations of the response of Mars to an interplanetary coronal mass ejection
Jakosky, B. M.; Grebowsky, J. M.; Luhmann, J. G. et al

in Science (2015), 350(6261),

Coupling between the lower and upper atmosphere, combined with loss of gas from the upper atmosphere to space, likely contributed to the thin, cold, dry atmosphere of modern Mars. To help understand ... [more ▼]

Coupling between the lower and upper atmosphere, combined with loss of gas from the upper atmosphere to space, likely contributed to the thin, cold, dry atmosphere of modern Mars. To help understand ongoing ion loss to space, the Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft made comprehensive measurements of the Mars upper atmosphere, ionosphere, and interactions with the Sun and solar wind during an interplanetary coronal mass ejection impact in March 2015. Responses include changes in the bow shock and magnetosheath, formation of widespread diffuse aurora, and enhancement of pick-up ions. Observations and models both show an enhancement in escape rate of ions to space during the event. Ion loss during solar events early in Mars history may have been a major contributor to the long-Term evolution of the Mars atmosphere. [less ▲]

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See detailEarly MAVEN Deep Dip campaign reveals thermosphere and ionosphere variability
Bougher, S.; Jakosky, B.; Halekas, J. et al

in Science (2015), 350(6261),

The Mars Atmosphere and Volatile Evolution (MAVEN) mission, during the second of its Deep Dip campaigns, made comprehensive measurements of martian thermosphere and ionosphere composition, structure, and ... [more ▼]

The Mars Atmosphere and Volatile Evolution (MAVEN) mission, during the second of its Deep Dip campaigns, made comprehensive measurements of martian thermosphere and ionosphere composition, structure, and variability at altitudes down to ~130 kilometers in the subsolar region. This altitude range contains the diffusively separated upper atmosphere just above the well-mixed atmosphere, the layer of peak extreme ultraviolet heating and primary reservoir for atmospheric escape. In situ measurements of the upper atmosphere reveal previously unmeasured populations of neutral and charged particles, the homopause altitude at approximately 130 kilometers, and an unexpected level of variability both on an orbit-To-orbit basis and within individual orbits. These observations help constrain volatile escape processes controlled by thermosphere and ionosphere structure and variability. [less ▲]

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See detailNew observations of molecular nitrogen in the Martian upper atmosphere by IUVS on MAVEN
Stevens, M. H.; Evans, J. S.; Schneider, N. M. et al

in Geophysical Research Letters (2015)

We identify molecular nitrogen (N2) emissions in the Martian upper atmosphere using the Imaging Ultraviolet Spectrograph (IUVS) on NASA's Mars Atmosphere and Volatile EvolutioN (MAVEN) mission. We report ... [more ▼]

We identify molecular nitrogen (N2) emissions in the Martian upper atmosphere using the Imaging Ultraviolet Spectrograph (IUVS) on NASA's Mars Atmosphere and Volatile EvolutioN (MAVEN) mission. We report the first observations of the N2 Lyman-Birge-Hopfield (LBH) bands at Mars and confirm the tentative identification of the N2 Vegard-Kaplan (VK) bands. We retrieve N2 density profiles from the VK limb emissions and compare calculated limb radiances between 90 and 210km against both observations and predictions from a Mars general circulation model (GCM). Contrary to earlier analyses using other satellite data, we find that N2 abundances exceed GCM results by about a factor of 2 at 130km but are in agreement at 150km. The analysis and interpretation are enabled by a linear regression method used to extract components of UV spectra from IUVS limb observations. © 2015. American Geophysical Union. All Rights Reserved. [less ▲]

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See detailThe structure and variability of Mars upper atmosphere as seen in MAVEN/IUVS dayglow observations
Jain, S. K.; Stewart, A. I. F.; Schneider, N. M. et al

in Geophysical Research Letters (2015)

We report a comprehensive study of Mars dayglow observations focusing on upper atmospheric structure and seasonal variability. We analyzed 744 vertical brightness profiles comprised of ∼109,300 spectra ... [more ▼]

We report a comprehensive study of Mars dayglow observations focusing on upper atmospheric structure and seasonal variability. We analyzed 744 vertical brightness profiles comprised of ∼109,300 spectra obtained with the Imaging Ultraviolet Spectrograph (IUVS) aboard the Mars Atmosphere and Volatile EvolutioN (MAVEN) satellite. The dayglow emission spectra show features similar to previous UV measurements at Mars. We find a significant drop in thermospheric scale height and temperature between LS = 218° and LS = 337-352°, attributed primarily to the decrease in solar activity and increase in heliocentric distance. We report the detection of a second, low-altitude peak in the emission profile of OI 297.2 nm, confirmation of the prediction that the absorption of solar Lyman alpha emission is an important energy source there. The CO2+ UV doublet peak intensity is well correlated with simultaneous observations of solar 17-22 nm irradiance at Mars. © 2015. American Geophysical Union. All Rights Reserved. [less ▲]

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See detailRetrieval of CO2 and N2 in the Martian thermosphere using dayglow observations by IUVS on MAVEN
Evans, J. S.; Stevens, M. H.; Lumpe, J. D. et al

in Geophysical Research Letters (2015)

We present direct number density retrievals of carbon dioxide (CO2) and molecular nitrogen (N2) for the upper atmosphere of Mars using limb scan observations during October and November 2014 by the ... [more ▼]

We present direct number density retrievals of carbon dioxide (CO2) and molecular nitrogen (N2) for the upper atmosphere of Mars using limb scan observations during October and November 2014 by the Imaging Ultraviolet Spectrograph on board NASA's Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft. We use retrieved CO2 densities to derive temperature variability between 170 and 220km. Analysis of the data shows (1) low-mid latitude northern hemisphere CO2 densities at 170km vary by a factor of about 2.5, (2) on average, the N2/CO2 increases from 0.042±0.017 at 130km to 0.12±0.06 at 200km, and (3) the mean upper atmospheric temperature is 324±22K for local times near 14:00. © 2015. American Geophysical Union. All Rights Reserved. [less ▲]

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See detailMAVEN IUVS observation of the hot oxygen corona at Mars
Deighan, J.; Chaffin, M. S.; Chaufray, J.-Y. et al

in Geophysical Research Letters (2015)

Observation of the hot oxygen corona at Mars has been an elusive measurement in planetary science. Characterizing this component of the planet's exosphere provides insight into the processes driving loss ... [more ▼]

Observation of the hot oxygen corona at Mars has been an elusive measurement in planetary science. Characterizing this component of the planet's exosphere provides insight into the processes driving loss of oxygen at the current time, which informs understanding of the planet's climatic evolution. The Mars Atmosphere and Volatile EvolutioN (MAVEN) Imaging Ultraviolet Spectrograph (IUVS) instrument is now regularly collecting altitude profiles of the hot oxygen corona as part of its investigation of atmospheric escape from Mars. Observations obtained thus far have been examined and found to display the expected gross structure and variability with EUV forcing anticipated by theory. The quality and quantity of the data set provides valuable constraints for the coronal modeling community. © 2015. American Geophysical Union. All Rights Reserved. [less ▲]

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See detailStudy of the Martian cold oxygen corona from the OI 130.4nm by IUVS/MAVEN
Chaufray, J. Y.; Deighan, J.; Chaffin, M. S. et al

in Geophysical Research Letters (2015)

First observations of the OI 130.4nm resonant line performed by the Imaging Ultraviolet Spectrograph (IUVS) aboard the Mars Atmosphere and Volatile EvolutioN mission (MAVEN) are presented in this paper ... [more ▼]

First observations of the OI 130.4nm resonant line performed by the Imaging Ultraviolet Spectrograph (IUVS) aboard the Mars Atmosphere and Volatile EvolutioN mission (MAVEN) are presented in this paper. This emission line is observed during the different orbit phases of MAVEN. The atomic oxygen density and the temperature at 200km are retrieved from an automatic pipeline using a radiative transfer model for resonant scattering lines for a selection of coronal profiles. These selected profiles are representative of the coronal scans done during the first months of the mission (from November 2014 to January 2015). The derived oxygen density and the temperature near the exobase are in the predicted range by the current thermospheric models of Mars for moderate solar activity, and some diurnal variations are observed. However, the absolute calibration of the instrument significantly limits the accuracy of density and temperature results. © 2015. American Geophysical Union. All Rights Reserved. [less ▲]

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