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The surface of the planet Mars exhibits a record of dessiccation and oxidation, the legacy of significant water escape to space as hydrogen and oxygen. This H escape can be constrained using ultraviolet observations of the planet's upper atmosphere, where neutral atomic hydrogen scatters UV sunlight. In the time since its orbit insertion in early 2021, the Emirates Mars Ultraviolet Spectrometer (EMUS) on the Emirates Mars Mission (EMM) has been observing this hydrogen at 102.6 nm and 121.6 nm, H Lyman beta and Lyman alpha. Here we present H escape rates retrieved from these observations, obtained using a 3D radiative transfer model that simulates the brightness of both spectral lines, combining their information content to constrain the atmospheric state. In agreement with past results, we find that H escape peaks around Southern Summer solstice, after perihelion, exhibiting a more than 10x increase relative to Northern Summer conditions. Importantly, our retrievals extract information about both the hydrogen density and temperature, and do not require independent assumptions about the upper atmosphere temperature. We will discuss prospects for extending these retrievals beyond the current EMM dataset as well as implications for the long-term evolution of the Mars atmosphere.

We present the first continuous observations of the extreme and far ultraviolet (EUV and FUV) dayglow emissions measured by Emirates Mars Ultraviolet Spectrometer (EMUS) onboard the Emirates Mars Mission. We found excellent agreement between the previous observations from the Hopkins Ultraviolet Telescope and recent observations by EMUS both in shape and magnitude. We presented the average disk brightness of major EUV and FUV emissions for about 10 months of data from April 2021 to February 2022. The solar activity was mild/minimum during the first half of the period presented in this study, but we noticed significant day-to-day variations in the major dayglow emissions independent of solar activity, indicating possible coupling from the lower atmosphere via waves/tides. The solar activity increased significantly during the second half of the study period. Our analysis showed that all major EUV and FUV emissions are highly correlated with solar forcing as well as seasonal changes. UAE government; NASA Published version Funding for the development of the Emirates Mars Mission mission was provided by the UAE government, and to co-authors outside of the UAE by MBRSC. Ed Thiemann, Phil Chamberlin, and Frank Eparvier are supported by NASA through the MAVEN project.

Water is lost from the Mars upper atmosphere to space as hydrogen and oxygen, both of which can be observed in scattered ultraviolet sunlight at 102.6 nm. We present Emirates Mars Mission Emirates Mars Ultraviolet Spectrometer (EMM/EMUS) insertion orbit observations of this airglow, resolving the independent altitude contributions of H and O for the first time. We present the first airglow modeling of the complete H and O 102.6 nm system and the first 3D azimuthally symmetric modeling of the O emission, retrieving temperatures and densities typical of northern spring. Our model reproduces the emission well above 200 km, but does not incorporate partial frequency redistribution needed to reproduce the observed O brightness at lower altitudes and on the disk. These results support future EMM/EMUS science orbit retrievals of H loss and the use of 102.6 nm observations to constrain planetary atmospheres across the solar system. UAE government; EMM/MBRSC; NASA through the MAVEN mission; KU-CU-LASP Space Sci. [8474000332] Published version Funding for development of the EMM mission was provided by the UAE government, and to co-authors outside of the UAE by MBRSC. Funding for the development of the radiative transfer model was provided by EMM/MBRSC and by NASA through the MAVEN mission. SR and KC are supported by the grant 8474000332-KU-CU-LASP Space Sci.

The Emirates Mars Ultraviolet Spectrometer (EMUS) instrument is one of three science instruments on board the “Hope Probe” of the Emirates Mars Mission (EMM). EMM arrived at Mars on February 9 2021, in order to explore the global dynamics of the Martian atmosphere, while sampling on both diurnal and seasonal timescales. The EMUS instrument is a far-ultraviolet imaging spectrograph, jointly developed by the Mohammed Bin Rashid Space Centre (MBRSC) in Dubai, UAE and the Laboratory for Atmospheric and Space Physics (LASP) at the University of Colorado Boulder, which measures emissions in the spectral range 100-170 nm. Using a combination of its one-dimensional imaging and spacecraft motion, it makes two-dimensional far-ultraviolet images of the Martian disk and near-space environment including the Lyman beta and alpha atomic hydrogen emissions (102.6 nm and 121.6 nm), two atomic oxygen emissions (130.4 nm and 135.6 nm), and the carbon monoxide fourth positive group band emission (140-170 nm). Measurements of radiance at these wavelengths are used to derive the column abundance of atomic oxygen and carbon monoxide in the Martian thermosphere, and the density of atomic oxygen and atomic hydrogen in the Martian exosphere both with spatial and sub-seasonal variability. We will present a survey of results from EMM/EMUS including observed variability in atomic oxygen and carbon monoxide emission, two kinds of aurora, and the status of atmospheric retrievals.

NASA’s Global-scale Observation of Limb and Disk’s (GOLD) instrument observed the July 2, 2019 total solar eclipse’s effect in the thermosphere from a geostationary orbit above South America. GOLD’s observations of compositional and neutral temperature changes induced by the eclipse are different from the modeled effects. Combined Thermospheric Ionospheric Electrodynamics General Circulation Model (TIE-GCM) and GLobal airglOW (GLOW) modeling of GOLD’s observation is relatively successful in reproducing morphologically changes. However, the model underestimates the compositional changes. GOLD observation show a ΣO/N2 column density ratio enhancement of ~ 80 % near the totality, but the model predicts ~ 10 % enhancement. This indicates that there are inadequacies in current modeling capabilities for thermospheric changes during an eclipse. GOLD’s thermospheric measurements provide an important, new test of the models. We will present detailed data-model comparisons of measurements versus modeling results for the July 2nd eclipse.