Mars Atmospheric Science with MMX

Martian Moons eXploration [MMX] is a mission dedicated to addressing open science questions about Phobos and Deimos, with a particular emphasis on Phobos on which MMX is set to land a small rover and to perform sample collection for return on Earth.

The unique orbit (coined quasi-stationary orbit) followed by MMX around Phobos is designed to optimize science operations around and on Phobos and to maximize scientific return during the three years of operation in the Martian system.

Using MMX instruments to study Mars' atmosphere will be possible during various opportunity windows during which observing Phobos will not be possible while observing Mars will be favourable.

The unique combination of MMX's extensive instrumentation and equatorial orbital configuration is a unique opportunity to broaden our understanding of the water and dust cycle on Mars.

It is unusual yet stimulating for atmospheric science on Mars to envision observations for which the community has only few grasp and flexibility on the observed season, with some seasons not being covered given complex operations dedicated to Phobos.

There is actually always something interesting to observe in the Martian atmosphere, and many knowledge gaps to close, provided a detailed strategy is put forward. Furthermore, the original point of view offered by MMX reinforces the interest of any opportunity to observe the Mars' atmosphere that could be possible within the observation plan.

Based on past observations and global-climate modeling, we will show how the observing opportunities of Mars' atmosphere with MMX could offer observations of the aphelion cloud belt (including vertical transport of water vapor, e.g. Fedorova et al. JGR planets 2020, and cloud activity) and dust storms on Mars (of various types: local, A, C, Z, global dust events -- see statistics by Battalio and Wang Icarus 2021 and Leseigneur et al. 2026) including possible fast-developing dusty convective events akin to rocket dust storms.

To achieve this goal, MMX instruments for atmospheric science  (Ogohara et al. Earth, Planets and Space 2022) feature the MIRS pushbroom near-infrared spectrometer with 10 km resolution per pixel and temporal resolution less than 1 hour (Barucci et al. 2025), as well as two cameras OROCHI (wide-angle, possible high-frequency monitoring) and TENGOO (telescopic, close-up views). MIRS may operate in nominal mode with continuous observation of the same area (with access to diurnal variability) global mapping mode of the sunlit hemisphere, tracking mode to study specific regions and transient events, as well as potential for limb scanning. The MSA ion analyzer offers perspectives to study atmospheric escape processes and their link to lower atmospheric processes, in particular dust storm activity (e.g., Heavens et al. Nature Geoscience 2018).

We will discuss possible observation plans for observing key features of the dust and water cycles on Mars, related to the aforementioned analysis. Other possible perspectives for Mars' atmospheric science include determining aerosol optical properties, mapping pressure using the CO2 absorption band, studying signatures in O2 dayglow, assessing CO concentration and trace gases, conducting exploratory science for instance about surface-atmosphere interactions.

Possible synergetic approaches of MMX observations, with past and present spectrometry and imagery to study Mars' atmosphere from orbit, or with in-situ landers and rovers, offer potentially fruitful approaches.