Subsatellite

[9] It has also been proposed that Saturn's satellite Iapetus possessed a subsatellite in the past; this is one of several hypotheses that have been put forward to account for its unusual equatorial ridge.

Such a scenario could have happened on the other giant-planet satellites as well, but only for Iapetus and perhaps Oberon would the resulting ridge have formed after the Late Heavy Bombardment and thus survived to the present day.

In 1988, the Soviet Union unsuccessfully attempted to put two robotic probes on quasi-orbits around the Martian moon Phobos.

Data collected by LRO have been described as essential for planning NASA's future human and robotic missions to the Moon.

Its detailed mapping program is identifying safe landing sites, locating potential resources on the Moon, characterizing the radiation environment, and demonstrating new technologies.