Inner moon

Thirty inner satellites are currently known, found orbiting around all four of the giant planets (Jupiter, Saturn, Uranus and Neptune).

Because of their small size, and glare from the nearby planet, they can be very difficult to observe from Earth.

These two moons share the same orbit, and the resulting confusion over their status was not resolved until the Voyager 1 flyby in 1980.

The innermost satellites orbit within the planetary rings, well within the fluid Roche limit, and only the internal strength and friction of their materials prevents them from being torn apart by tidal forces.

In the distant future these moons will impact the planet or penetrate deeply enough within their Roche limit to be tidally disrupted into fragments.

Unconfirmed bodies orbiting close to Saturn's F ring, such as S/2004 S 6, may be somewhat smaller moons, if they are not transient clumps of dust instead.

Inner satellites are all tidally locked, that is, their orbit is synchronous with their rotation so that they only show one face toward their parent planet.

All the inner satellites of Jupiter, Uranus, and Neptune have very dark surfaces with an albedo between 0.06 (Metis) and 0.10 (Adrastea).

This is thought to be because their surfaces are being coated with fresh ice particles swept up from the ring system within which they orbit.

As a result, it has been estimated that very small bodies in inner orbits are expected to be disrupted by external impactors on a timescale much shorter than the age of the solar system.

Further evidence for such a process may include the low density of these bodies (due, perhaps, to the looseness of material so accumulated), and their high albedo.

Jupiter has the smallest set of inner satellites, including only the following four: The Galileo spacecraft may have observed some moonlets near Amalthea's orbit.

These were strongly perturbed by Triton in the period soon after that moon's capture into a very eccentric initial orbit.