References of "Deighan, J"
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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 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 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 detailGlobal Simulation of UV Atmospheric Emissions
González-Galindo, F.; López-Valverde, M. A.; Forget, F. et al

Conference (2017, January 17)

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See detailThe structure and variability of Mars dayside thermosphere from MAVEN NGIMS and IUVS measurements: Seasonal and solar activity trends in scale heights and temperatures
Bougher, S. W.; Roeten, K. J.; Olsen, K. et al

in Journal of Geophysical Research. Space Physics (2017)

Mars dayside thermospheric temperature and scale height trends were examined using measurements from the Neutral Gas Ion Mass Spectrometer (NGIMS) and the Imaging Ultraviolet Spectrograph (IUVS) on the ... [more ▼]

Mars dayside thermospheric temperature and scale height trends were examined using measurements from the Neutral Gas Ion Mass Spectrometer (NGIMS) and the Imaging Ultraviolet Spectrograph (IUVS) on the Mars Atmosphere Volatile EvolutioN (MAVEN) spacecraft. Average scale heights (over 150-180 km for solar zenith angles ≤75°) from several different sampling periods were obtained from each instrument. NGIMS and IUVS scale height trends were found to be in good agreement, with both showing scale heights decreasing after perihelion and reaching a low value near aphelion (13.6 to 9.4 km). Between these two seasonal extremes, the temperature decreased by ∼70 K (from 240 to 170 K). These trends were also analyzed with respect to the changing solar flux reaching the planet, using the Lyman alpha irradiance measured by the Extreme Ultraviolet Monitor (EUVM) on MAVEN. Scale heights responded strongly to the changing solar flux. During this part of the MAVEN mission (October 2014 to May 2016), it was concluded that over longer timescales (at least several months), dayside thermospheric temperatures are chiefly driven by changing solar forcing, although it is the effects of changing heliocentric distance rather than changing solar activity which seem to have the greatest impact. Furthermore, effects of solar forcing were not observed on shorter timescales (less than a month), suggesting local wave effects may dominate solar forcing on these timescales. Finally, temperatures from two NGIMS sampling periods were compared to temperatures from the Mars Global Ionosphere-Thermosphere Model (M-GITM) and found to be in good agreement. © 2017. American Geophysical Union. All Rights Reserved. [less ▲]

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See detailThe Martian diffuse aurora: Monte Carlo simulations and comparison with IUVS-MAVEN observations
Gérard, Jean-Claude ULiege; Soret, Lauriane ULiege; Schneider, N. et al

Conference (2016, December)

A new type of Martian aurora, characterized by an extended spatial distribution, an altitude lower than the discrete aurora and electron precipitation up to 200 keV has been observed following solar ... [more ▼]

A new type of Martian aurora, characterized by an extended spatial distribution, an altitude lower than the discrete aurora and electron precipitation up to 200 keV has been observed following solar activity on several occasions with the IUVS on board the MAVEN spacecraft. We describe the results of Monte Carlo simulations of the production of several ultraviolet and visible auroral emissions for initial electron energies from 0.1 to 200 keV. These include the CO2+ ultraviolet doublet (UVD) at 288.3 and 289.6 nm and the Fox–Duffendack–Barker (FDB) bands, CO Cameron and Fourth Positive bands, OI 130.4 and 297.2 nm and CI 156.1 nm and 165.7 nm multiplets. We calculate the nadir and limb intensities of several of these emissions for a unit precipitated energy flux. Our results indicate that electrons in the range 100-200 keV produce maximum CO2+ UVD emission near 75 km. We combine SWEA and SEP electron energy spectra measured during diffuse aurora to calculate the volume emission rates and compare with IUVS observations of the emission limb profiles. The strongest predicted emissions are the CO2+ FDB, UVD and the CO Cameron bands. The metastable a 3Π state which radiates the Cameron bands is deactivated by collisions below ~110 km. As a consequence, we show that the CO2+ UVD to the Cameron bands ratio increases at low altitude in the energetic diffuse aurora. [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 detailMAVEN's Imaging Spectrograph and the Legacy of Charles Barth
Schneider, Nick; McClintock, W; Stewart, I et al

Scientific conference (2015, May 15)

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See detailDiscovery of Diffuse Aurora on Mars
Schneider, Nick; Stiepen, Arnaud ULiege; Jain, S et al

Conference (2015)

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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 detailProbing the Martian atmosphere with MAVEN/IUVS stellar occultations
Gröller, H.; Yelle, R. V.; Koskinen, T. T. et al

in Geophysical Research Letters (2015)

The first campaign of stellar occultations with the Imaging Ultraviolet Spectrograph (IUVS) instrument on board of Mars Atmosphere and Volatile EvolutioN (MAVEN) mission was executed between 24 and 26 ... [more ▼]

The first campaign of stellar occultations with the Imaging Ultraviolet Spectrograph (IUVS) instrument on board of Mars Atmosphere and Volatile EvolutioN (MAVEN) mission was executed between 24 and 26 March 2015. From this campaign 13 occultations are used to retrieve CO2 and O2 number densities in the altitude range between 100 and 150 km. Observations probe primarily the low-latitude regions on the nightside of the planet, just past the dawn and dusk terminator. Calculation of temperature from the CO2 density profiles reveals that the lower thermosphere is significantly cooler than predicted by the models in the Mars Climate Database. A systematically cold layer with temperatures of 105-120 K is seen in the occultations at a pressure level around 7 × 10-6 Pa. © 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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See detailThree-dimensional structure in the Mars H corona revealed by IUVS on MAVEN
Chaffin, M. S.; Chaufray, J. Y.; Deighan, J. et al

in Geophysical Research Letters (2015)

Loss of water to space via neutral hydrogen escape has been an important process throughout Martian history. Contemporary loss rates can be constrained through observations of the extended neutral ... [more ▼]

Loss of water to space via neutral hydrogen escape has been an important process throughout Martian history. Contemporary loss rates can be constrained through observations of the extended neutral hydrogen atmosphere of Mars in scattered sunlight at 121.6 nm. Historically, such observations have been interpreted with coupled density and radiative transfer models, inferring escape fluxes from brightness profiles gathered by flybys, orbiters, and telescope observations. Here we demonstrate that the spherical symmetry assumed by prior analyses cannot reproduce observations by the Imaging Ultraviolet Spectrograph (IUVS) on the Mars Atmosphere and Volatile EvolutioN (MAVEN) mission. We present unique observations of the Mars H corona to large radial distances and mapping results from initial MAVEN science at Mars. These observations represent the first detection of three-dimensional structure in the H corona of Mars, with implications for understanding the atmosphere today and the loss of H to space throughout Martian history. © 2015. American Geophysical Union. All Rights Reserved. [less ▲]

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