moonlets

Moonlets are small natural satellites, typically defined as bodies that orbit a planet or dwarf planet but are much smaller than the system’s major moons. They can range from tens of meters to hundreds of kilometers in diameter and often have irregular shapes. The term is frequently used for very small satellites in planetary ring systems and for small companions to asteroids.

Moonlets can form by accretion within a circumplanetary disk during the early stages of planet formation, by fragmentation from impacts, or by capture of passing bodies. In rings and dense debris disks, moonlets may grow from aggregates of ring particles or be remnants of larger bodies. Their gravity can perturb surrounding material, creating gaps, waves, and sharp edges in rings, or altering the orbits of nearby satellites.

Observationally, moonlets are detected by spacecraft imaging, by dynamical effects on rings, or by mutual events in binary systems. They are often irregular in shape and possess low surface gravity, which influences their surface geology and rotational states, including possible tidal locking.

Examples include small moons within ring regions that sculpt gaps and edges, as well as tiny natural satellites that orbit asteroids. The concept is also used in discussions of planet formation, where moonlets may act as building blocks that can coalesce into larger moons over time.