Retrieval of Ar, N2, O, and CO in the Martian thermosphere using dayglow limb observations by EMM EMUS

The Emirates Ultraviolet Spectrometer (EMUS) onboard the Emirates Mars Mission (EMM) Hope probe images Mars at wavelengths extending from approximately 100 to 170 nm. EMUS observations began in February 2021 and cover over a full Mars year. We report the first limb scan observations at Mars of ultraviolet emissions Ar I 106.6 nm, N I 120 nm, and carbon monoxide (CO) Fourth Positive Group (A - X) band system excited by electron impact on CO. We use EMUS limb scan observations to retrieve number density profiles of argon, molecular nitrogen, atomic oxygen, and CO in the upper atmosphere of Mars from 130 to 160 km. CO is a sensitive tracer of the thermal profile and winds in Mars' middle atmosphere and the chemistry that balances CO2 in the atmosphere of Mars. EMUS insertion orbit special observations demonstrate that far ultraviolet limb measurements of the Martian thermosphere can be spectroscopically analyzed with a robust retrieval algorithm to further quantify variations of CO composi..., , , # Retrieval of Ar, N2, O, and CO in the Martian Thermosphere Using Dayglow Limb Observations by EMM EMUS

[https://doi.org/10.5061/dryad.dv41ns253](https://doi.org/10.5061/dryad.dv41ns253)

The data set contains altitude profiles of observed (kiloRayleighs) and retrieved intensities (Rayleighs) and number densities (cm-3) for Ar, N2, O, and CO for eight EMM insertion orbit observations. The density retrieval method is described by Evans et al. (2015; doi:10.1002/2015GL065489) and Evans et al. (2023; doi:10.1029/2022JE007325).

## Description of the data and file structure

The observed intensities are stored in ASCII files contained within a compressed tar file (emus_data.tgz). Retrieved intensities and densities are stored in ASCII files contained within a separate compressed tar file (retrieval_data.tgz). The folder names provide the EMUS observation date and time.

The content of each intensity file (Ar1066.txt, CO4PGfull.txt, NI1200.txt, OI1356.txt) is described within the file. The...