Moonlet

Origin

From moon + the diminutive suffix -let.

Full definition of moonlet

Noun

1. (astronomy) a very small body orbiting a planet, often as part of a ring.
• 1981, Nature http://books.google.com/books?id=5KEoAAAAMAAJ&q=define:moonlet&dq=define:moonlet&pgis=1:"A moonlet within the ring system will exert a systematic torque on ring material."