Japan’s MMX Mission: New Surface Atlas to Guide Phobos Sample Collection

The Japan Aerospace Exploration Agency’s Martian Moons eXploration mission, launching toward the Red Planet, has received a critical navigational upgrade. Researchers have published a comprehensive 3D morphodynamic surface atlas of Phobos. Developed using the RAVEL software code by Isabel Herreros and Sébastien Charnoz, this new model maps Regolith Migration Pathways to help the MMX spacecraft pinpoint optimal touchdown zones for collecting the first-ever samples from a Martian moon.

Decoding the Low-Gravity Dynamics of Phobos

Phobos exists in a complex mechanical environment. Unlike terrestrial bodies where simple gravitational pull dictates where loose dirt settles, this Martian moon operates under a equilibrium of self-gravity, time-dependent Martian tides, and inertial forces. In such a low-gravity regime, traditional topographic slope mapping falls short. Loose surface material cannot be inferred from topographic slope alone.

To solve this, the morphodynamic atlas applies a dynamical model. According to research detailed in the paper, the RAVEL code combines surface acceleration fields with friction applied directly to a digital terrain model of Phobos. Rather than trying to predict the triggering of slope failure, the model calculates where material would preferentially move once motion has been initiated.

Mapping Regolith Migration Pathways

The computational results expose a sparse network of preferred surface transport routes termed Regolith Migration Pathways. These RMPs dictate the redistribution of regolith across the moon.

The final positions of these pathways correlate with smooth, low-relief terrains and spectrally neutral units. These zones act as depositional mantles formed by long-term regolith infill. Conversely, rough, high-standing areas featuring abundant small craters and blue spectral slopes correspond to dynamically active or denuded source regions. Meanwhile, spectrally red terrains map to dynamically quiet, morphologically rough surfaces where the model predicts negligible regolith motion, suggesting older, less frequently reworked units.

Operational Impact for the MMX Spacecraft

Understanding these dynamics is a constraint for the mission. JAXA’s MMX spacecraft needs to collect samples. By mapping out where material collects via RMPs, mission planners can constrain the geographical provenance of samples to be collected by the MMX spacecraft.

Engineering Precision for Interplanetary Sampling

Building an atlas capable of guiding a landing sequence requires computational modeling. The interaction between tidal forces from Mars and the self-gravity of the body creates localized acceleration vectors. As the MMX mission progresses toward its operational phase, this dataset will be useful for constraining the geographical provenance of samples.