Exogeology

Exogeology is the scientific study of the geology of planetary bodies beyond Earth, including planets, moons, asteroids, comets, and dwarf planets, as well as the processes that shape their surfaces and interiors. The field overlaps with planetary geology and astrogeology and is concerned with understanding how geological activity and history vary across the solar system and, in some discussions, around exoplanets as data allow.

Core objectives include mapping surface geology, characterizing crustal structure, and unraveling geological histories through volcanism, tectonics, impact cratering, erosion, sedimentation, and, on icy worlds, cryovolcanism and ice tectonics. Exogeology uses geological timelines—crater dating, stratigraphy, and differentiations of crust and mantle—to reconstruct evolutionary sequences. It also studies geochemical and geophysical signatures, including gravity and magnetic fields, to infer internal processes.

Methods and data are drawn from remote sensing, high-resolution imaging, spectroscopy, radar sounding, and, where possible, in situ measurements from landers and rovers or sample analyses. Laboratory work on Earth, meteorite studies, and modeling support interpretation. Space missions provide primary data, including lunar and planetary orbiter observations, lander and rover results, and targeted studies of asteroids and comets (for example, data from missions to the Moon, Mars, Mercury, asteroid Bennu, and comet 67P/Churyumov-Gerasimenko). Notable missions include Cassini, Dawn, Rosetta, MESSENGER, and New Horizons.

In exoplanet contexts, geology is inferred indirectly through mass–radius relations, density, atmospheric composition, and thermal evolution models, as direct surface data remain unavailable. Exogeology contributes to understanding solar system formation, planetary evolution, habitability, and future exploration and resource utilization.