KHALIFA UNIVERSITY STUDY: THE FIRST LIMBS SCAN OBSERVATION OF MARS CO MOLECULE

Dr. Nayla El Kork (Associate professor at the Department of Physics at Khalifa University) and her research group, provided insightful data to the EMM ( Emirates Mars Mission) science team for a better analysis of spectra collected by the Emirates Mars Ultraviolet Spectrometer (EMUS), onboard the EMM spacecraft, better known as the HOPE probe. EMUS is used to image the upper atmosphere of Mars at wavelengths extending from approximately 100 to 170 nm.

This work was presented at the AGU annual meeting 2023 under the paper entitled, “P51E-2749 Retrieval of Ar (Argon), N2 (Nitrogen), O (Oxygen), and CO₂ (Carbon Dioxide) in the Martian Thermosphere Using Dayglow Limb Observations by the Emirates Mars Ultraviolet Spectrometer”. This investigation reports the first limbs scan observation at Mars of ultraviolet emissions Ar I 106.6 nm, N I 120 nm, and carbon monoxide (CO) Hopfield-Birge C–X (0,0) at 108.8 nm and E–X (0,0) at 107.6 nm.

Limb scan observation can be understood by considering the term “Atmospheric Limb”. The term represents the outer edge or boundary of a planet›s atmosphere as viewed from space.

When observing a planet from a distance, such as from a spacecraft or satellite, the atmosphere appears as a thin layer surrounding the planet. The limb is the apparent edge of this atmospheric layer as seen against the backdrop of space.

As such, a limb scan observation involves systematically scanning or profiling a planet›s atmosphere along its limb, or outer edge, from a spacecraft or satellite. In the case of EMUS onboard the HOPE probe, special observations were designed for the EMM insertion orbit to allow for atmospheric limb scans.

According to El Kork, the molecular CO emission lines obtained in collaboration with the ExoMol team were used by the EMM team to understand the abundance of atoms and molecules on Mars.

El Kork states, “The research will be used to understand the Martian atmosphere›s composition better. More specifically, the UV emission lines we calculate are used to better analyze the spectra recorded by the Emirates Mars Ultraviolet spectrometer onboard the HOPE probe.”

Emission profiles of different species in the Martian atmosphere can be very hard to analyze, and the work provided ways to distinguish between emissions of different constituents, in the deconvolution process. As such, the research helped to better understand the composition and emission properties of Mars constituent atoms and molecules.

The EMUS limb scan observations were used to retrieve altitude profiles of number density for argon, molecular nitrogen, atomic oxygen, and CO in the upper atmosphere of Mars.

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.

The CO number densities retrieved from EMUS observations provide an important first step towards filling a gap in the knowledge of the abundance of CO and its variability at altitudes from 100 to 160 km.

Importance of studying

CO emissions

The importance of studying CO emissions is that it offers better knowledge about interactions between the lower and higher atmosphere of Mars.

El Kork explains, “Our research comes in as a continuation to the MAVEN mission, which aimed to understand the structure, composition, and dynamics, of the Martian atmosphere, as well as to investigate how the loss of volatile compounds, such as water and carbon dioxide, has affected the planet›s climate over time. In other words, this research allows us to better understand the depletion processes, which are thought to be responsible for the transformation of Mars from a rich water containing planet into the current arid one.”

The depletion can be attributed to many processes, one of which is the photochemical dissociation of Carbon Dioxide, the most abundant gas on the red planet, into Carbon Monoxide molecules and Oxygen atoms.

El Kork states, “CO molecule is consequently a very important indicator in the atmospheric chemistry of Mars and knowledge about its abundance provides insights into such complex chemical processes happening in the atmosphere, including interactions with other gasses and the influence of solar radiation. This was an essential component of both the EMM and MAVEN missions.”

The effect on UAE Mars Mission

This research falls directly into the theme of the UAE MARS mission. The research helped to elucidate the hidden information about the Martian atmospheric limb including Nitrogen, Argon and CO emissions.

El Kork elaborates, “This data is of high importance in the understanding of the different chemical and photochemical processes that take place in the Martian atmosphere, at different altitudes, an important piece of the puzzle in our quest for Martian atmosphere exploration”.

In terms of future missions such as the UAE Asteroid Mission, El Kork believes that while different in nature, she is still considering ways to which they can make a contribution.

A journal paper including these results will soon be available to the scientific community and the audience interested in the subject.