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

Abstract

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

Retrieval of Ar, N2, O, and CO in the Martian Thermosphere Using Dayglow Limb Observations by EMM EMUS

“…It is worth mentioning that Feldman et al (2000) and Krasnopolsky and Feldman (2002) ignored multiple scattering and photoelectron impact excitation in their analyses. However, Lootah et al (2022) concluded that the Ar I 106.6 nm emission is optically thick to self-absorption in the Martian thermosphere.…”

“…However, Lootah et al. (2022) concluded that the Ar I 106.6 nm emission is optically thick to self‐absorption in the Martian thermosphere.…”