Thebe (moon)

Physical characteristics

Thebe is irregular in shape and appears heavily cratered and scarred, typical of small moons that lack sufficient gravity to become spherical. Its dimensions are roughly on the order of a few dozen to a few hundred kilometres across (often quoted as roughly 116×98×84 km), and it is believed to be composed of a mixture of rock and ice with a relatively low bulk density. The surface has a reddish tint, similar to that of the nearby moon Amalthea, suggesting space weathering or deposition of sulfur and other material transported within Jupiter's magnetosphere.

Orbit and dynamical role

Thebe orbits Jupiter inside the orbit of the Galilean satellites and just outside the orbit of Amalthea, completing one circuit in less than a Jovian day. It is thought to be tidally locked, keeping the same face toward the planet. Impacts on Thebe continually eject fine particles that have formed and sustain a faint, diffuse structure known as the Thebe gossamer ring; the moon therefore plays an active role in shaping Jupiter's ring system.

Discovery, name, and exploration

Stephen P. Synnott first identified Thebe in Voyager imagery; the designation S/1979 J 2 was used until the International Astronomical Union gave it the name Thebe in 1983. The name honors the mythological nymph Thebe, a daughter of the river god Asopus and a lover of Zeus. After Voyager, the Galileo orbiter obtained higher-resolution images that improved knowledge of Thebe's shape, surface features and orbital parameters.

Importance and notable facts

• Thebe is a source of dust for Jupiter's gossamer rings, linking small moons and ring dynamics.
• Its irregular shape and surface features provide clues about collisional history in the inner Jovian system.
• As an inner moon, Thebe helps scientists understand tidal interactions, space weathering, and the distribution of material around a giant planet.

Although small and faint, Thebe is an integral part of Jupiter's complex system of satellites and rings. Future missions and observations may refine its dimensions, composition and the processes that feed Jupiter's faint rings.