If the microprobes work, the effort will pave the way for new studies of Mars and other planets and planetary moons.

There's a lump of rock orbiting it, too - about the size of a planetary moon.

Most of the books focus on the exploration of one particular planet or planetary moon.

Like most other regular planetary moons, Callisto's rotation is locked to be synchronous with its orbit.

A few, like the ones in the big planetary moons, are relatively fixed, but mostly things shift and change.

They are not as clearly distinguished as planetary moons, sometimes being almost as large as their partners.

Most of the planetary moons probably formed from the discs of gas and dust circulating around planets in the early solar system.

New objects were also introduced such as hidden storage containers with free items, planetary moons, particle nebula clouds, and wormholes.

It was the last planetary moon to be discovered directly by visual observation.

Odd fragments and planetary moons, as well as everything else, are now "small solar system bodies."