Hope Probe observes abundance of carbon monoxide that will redefine Martian atmosphere

Yamama Badwan, Staff Reporter

The Emirates Mars Ultraviolet Spectrometer onboard the Emirates Mars Mission observes light in a wavelength region referred to as far ultraviolet.

This study focuses on far ultraviolet light that is produced by carbon monoxide (CO).

Observations of far ultraviolet light can be used to determine the relative abundance of CO in the upper atmosphere of Mars.

Variations in the relative abundance of CO over time and across different locations can provide valuable information regarding the temperatures and winds in the middle atmosphere of Mars, as well as the chemistry that balances the whole atmosphere of Mars.

This study presents a method for converting observations of far ultraviolet light into relative abundances of CO in the upper atmosphere of Mars.

Carbon monoxide (CO) plays a major role in the chemical cycles of CO2, hydrogen, and oxygen, and is a tracer of the thermal profile and winds in the Martian middle atmosphere. With a mean lifetime of about 6 Mars years (Krasnopolsky, 2007), CO is produced primarily through CO2 photolysis in the middle atmosphere and is effectively lost in the lower atmosphere through catalysis by the OH radical produced by water vapor (H2O) photolysis.

Given such a long lifetime (relative to one Mars year), no variation of CO with local time is expected. However, as an incondensable, CO is expected to vary both locally and temporally with Mars season.

 The spatial distribution of CO is therefore an important quantity that can be used to constrain models of photochemical and dynamical processes in the Martian atmosphere.

Indeed, the model predicted long-term equilibrium value for the CO volume mixing ratio is smaller than observed by a factor two to four (Lefèvre & Krasnopolsky, 2017).

This disagreement suggests that our understanding of Martian atmospheric chemistry remains incomplete (Olsen et al., 2021).