Research project P4S/251/MAESTRO (Research action P4S)
The MAESTRO project aims to advance our understanding of the internal structure of small Solar System bodies such as asteroids, comets, and irregular moons, by developing innovative methods to invert geodetic observations into three-dimensional density distributions. Determining the interior structure of these objects is essential for reconstructing the history and evolution of the Solar System. As remnants of planetary formation, they preserve valuable records of the physical and chemical conditions that prevailed during its earliest stages.
Investigating their interiors can reveal whether these bodies are solid monoliths, layered objects, or rubble piles, and whether they contain features such as voids, ice-rich layers, or subsurface reservoirs that generate complex gravitational and dynamical signatures. By combining gravity, rotational, and tidal information derived from spacecraft precise orbit determination with radar imaging, seismic measurements, and other in-situ observations, it becomes possible to probe these hidden structures and refine models of small-body formation and evolution. Knowledge of their interiors is also critical for planetary-defence strategies, resource assessment, and the planning of future exploration missions, including sample-return campaigns and potential asteroid-mining activities.
At the heart of MAESTRO lies GILA, a gravity inversion framework developed at the Royal Observatory of Belgium and UCLouvain that currently estimates subsurface density variations from gravity-field measurements and shape models. A central objective of the project is to extend GILA by integrating additional datasets that provide complementary constraints on interior structure. In addition to traditional gravity-field information, the enhanced framework will incorporate local gravity measurements, generalized moments of inertia, radar and seismic sounding data, as well as a priori constraints from geological maps, thermal-inertia observations, and tidal deformation measurements. Following its development and validation, the upgraded GILA framework will be applied to data acquired by the Hera and MMX missions, which are expected to arrive at Didymos in November 2026 and at Phobos in mid-2027, respectively. If either mission fails to deliver the anticipated datasets, the project will still yield valuable results by analysing observations from previous missions to Bennu, Ryugu, Eros, and comet 67P/Churyumov–Gerasimenko, leading to refined interior models of these bodies. GILA will also be used to perform simulations supporting the preparation of the RAMSES and OSIRIS-APEX missions targeting asteroid Apophis during its 2029 Earth flyby.
Ultimately, the MAESTRO project seeks to deliver an open, well-documented, and community-accessible scientific framework capable of jointly exploiting diverse geophysical observations to infer the interior structure of small bodies.
