Morphology of Extreme and Far Ultraviolet Martian Airglow Emissions Observed by the EMUS Instrument on Board the Emirates Mars Mission

Jain, Sonal; Deighan, Justin; Chaffin, Michael; Holsclaw, G. M.; Lillis, Robert J.; Fillingim, M. O.; Evans, J. Scott; Correira, J.; Matroushi, Hessa Al; Lootah, Fatma; England, S.; AlMazmi, Hoor; Thiemann, E.; Chamberlin, Phillip C.; Eparvier, F.

doi:10.1029/2022gl099885

Cited by 4 publications

(4 citation statements)

References 27 publications

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“…The discrepancy between the values could be due to HUT observations covering northern latitudes, where we expect less of Ar as it increases closer to the southern latitudes (see Section 3.4). In addition, EMUS data shows a geophysical variability on the order of 20%, which may contribute to the difference between EMUS and HUT values (see England et al., 2022, this issue, and Jain et al., 2022, this issue). We also note that FUSE values at a similar L S are substantially brighter than those measured by EMUS.…”

Section: Resultsmentioning

confidence: 99%

“…In this paper, we have considered data up to the end of January 2022, due to an issue of reducing the Lyman‐α past that date (Jain et al., 2022, this issue). Specifically for our analysis of Ar I 106.6 nm variability due to geometrical, seasonal and temporal factors we utilize EMUS L2b data captured by U‐OS1 at the following conditions: Data set 1: Observed on 2021/07/02 at L s 66.4° at a phase angle of 19°, as seen in Figure 1. Data set 2: Observed on 2021/12/24 at L s 146.8° at a phase angle of 40°. …”

Section: Data Set Specificationsmentioning

confidence: 99%

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Emirates Mars Ultraviolet Spectrometer's (EMUS) Observation of Argon in the Martian Thermosphere

Lootah

Deighan

Fillingim

et al. 2022

Geophysical Research Letters

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EMM is designed to explore the dynamics of the Martian atmospheric layers on a global scale, simultaneously sampling diurnal, and seasonal timescales (Almatroushi et al., 2021;Amiri et al., 2022). On board the EMM's spacecraft "Hope Probe" are three scientific instruments designed to study these different layers: (a) Emirates eXploration Image (EXI) (Jones et al., 2021) (b) Emirates Infrared Spectrometer (EMIRS) (Edwards et al., 2021) and (c) Emirates Mars Ultraviolet Spectrometer (EMUS) (Holsclaw et al., 2021). EMUS is a far ultraviolet imaging spectrometer designed to investigate the abundance and spatial variability of key neutral species in the thermosphere (100-200 km) and in the exosphere (≥200 km). The EMUS wavelength range is from 100 to 170 nm, detecting key emissions in the upper atmosphere of Mars such as oxygen (135.6 nm, 130.4 nm), hydrogen (Lyman-β: 102.6 nm, Lyman-α: 121.6 nm), carbon monoxide Fourth Positive Group band system (140-170 nm) and argon (104.8 nm, 106.6 nm) (Holsclaw et al., 2021). Motivation to Study Argon on MarsArgon is a photochemically inert gas with molecular weight of 40 g/mol, close to carbon dioxide's (CO 2 ) 44 g/ mol, but does not condense at the temperatures found in the Martian atmosphere. This causes an apparent accumulation of Ar at the winter poles as CO 2 condenses near the surface, and this compositional change propagates to the upper atmosphere, making Ar/CO 2 mixing ratios a useful indicator of vertical transport in the atmosphere of Mars. Understanding the distribution of Ar has been of interest to scientists for some time, as it is a good

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Section: Resultsmentioning

confidence: 99%

Section: Data Set Specificationsmentioning

confidence: 99%

Emirates Mars Ultraviolet Spectrometer's (EMUS) Observation of Argon in the Martian Thermosphere

Lootah

Deighan

Fillingim

et al. 2022

Geophysical Research Letters

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“…(2022), and a comparison of the EMUS L2A spectrum to Feldman et al., 2000 is shown in Jain et al. (2022).…”

Section: Datamentioning

confidence: 89%

Spatio‐Temporal Structure of Far Ultraviolet Martian Dayglow Observed by EMM‐EMUS

England

Jain

Deighan

et al. 2022

Geophysical Research Letters

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Mars' ultraviolet dayglow has been used to study its upper atmosphere for over four decades. Identifying variations in emission features has provided information on composition, density, and temperature. The Emirates Mars Ultraviolet Spectrometer onboard the Emirates Mars Mission observes Mars' dayglow at Far and Extreme UV wavelengths. Variations in disk emission features are studied, with a focus on O I 130.4, CO Fourth Positive Group and C I 156.1 nm. All show variations with local time (LT) and emission angle as expected. Dawn‐dusk asymmetry observed is attributed to LT differences in advection. Variations in the brightness of several dayglow features, including 130.4 nm, with irregular shapes are noted in around 25% of the disk images. These display some LT and hemispheric asymmetry in their occurrence rates. Examination of their spatial structure, occurrence, and spectra suggests these are associated with variations in composition and photoelectron flux.

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“…Hydrogen Lyman alpha (HI 121.6 nm) is by far the brightest emission line in EMUS data, and all other emissions are sitting either on the shorter wavelength side or the longer wavelength side of this bright emission feature. Hence, the spectral smearing of an atomic line is characterized by the instrument Line Spread Function (LSF) (Chaffin et al, 2015(Chaffin et al, , 2018Deighan et al, 2015;Jain et al, 2022). This background is subtracted by calculating the baseline fit based on the shorter wavelength and longer wavelength sides of 130.4 nm core, that falls on the Lyman alpha wing, but not on the 130.4 nm emission feature itself.…”

Section: Emus Cross Exospheric and Background Observationsmentioning

confidence: 99%

EMM EMUS Observations of Hot Oxygen Corona at Mars: Radial Distribution and Temporal Variability

Chirakkil,

Deighan,

Chaffin

et al. 2024

JGR Space Physics

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We present the first observations of the dayside coronal oxygen emission in far ultraviolet (FUV) measured by the Emirates Mars Ultraviolet Spectrometer (EMUS) onboard the Emirates Mars Mission (EMM). The high sensitivity of EMUS is providing an opportunity to observe the tenuous oxygen corona in FUV, which is otherwise difficult to observe. Oxygen resonance fluorescence emission at 130.4 nm provides a measurement of the upper atmospheric and exospheric oxygen. More than 500 oxygen corona profiles are constructed using the long–exposure time cross–exospheric mode (OS4) of EMUS observations. These profiles range from ∼200 km altitude up to several Mars radii (>6 RM) across all seasons and for two Mars years. Our analysis shows that OI 130.4 nm is highly correlated with solar irradiance (solar photoionizing and 130.4 nm illuminating irradiances) as well as changes in the Sun–Mars distance. The prominent short term periodicity in oxygen corona brightness is consistent with the solar rotation period (quasi–27–day). A comparison between the perihelion seasons of Mars Year (MY) 36 and MY 37 shows interannual variability with enhanced emission intensities during MY 37, due to the rise of Solar Cycle 25. These observations show a highly variable oxygen corona, which has significant implications on constraining the photochemical escape of atomic oxygen from Mars.

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Morphology of Extreme and Far Ultraviolet Martian Airglow Emissions Observed by the EMUS Instrument on Board the Emirates Mars Mission

Cited by 4 publications

References 27 publications

Emirates Mars Ultraviolet Spectrometer's (EMUS) Observation of Argon in the Martian Thermosphere

Emirates Mars Ultraviolet Spectrometer's (EMUS) Observation of Argon in the Martian Thermosphere

Spatio‐Temporal Structure of Far Ultraviolet Martian Dayglow Observed by EMM‐EMUS

EMM EMUS Observations of Hot Oxygen Corona at Mars: Radial Distribution and Temporal Variability

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