Subsatellite

Subsatellite is a satellite (artificial or natural) that orbits a natural satellite, i.e. a "moon of a moon". There are no known natural subsatellites in the Solar System. In most cases, the tidal effects of the primary would make such a system unstable.

Rhea

Artist impression of Rhea's rings

The possible detection[1] of a ring system around Saturn's natural satellite Rhea lead to calculations that indicated that satellites orbiting Rhea would have stable orbits. Furthermore, the suspected rings are thought to be narrow,[2] a phenomenon normally associated with shepherd moons. However, targeted images taken by the Cassini spacecraft failed to detect any rings associated with Rhea.[3]

Iapetus

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 equatorial ridge.[4]

Artificial subsatellites

Many spacecraft have orbited the Moon, including manned craft of the Apollo program. As of 2016 none have orbited other moons, though several unmanned attempts have been made for Phobos.

References

  1. ↑ "The Dust Halo of Saturn's Largest Icy Moon, Rhea – Jones et al. 319 (5868): 1380 – Science". Retrieved 2008-03-06.
  2. ↑ "Saturn satellite reveals first moon rings – 06 March 2008 – New Scientist". Retrieved 2008-03-06.
  3. ↑ http://www.agu.org/pubs/crossref/2010/2010GL043663.shtml
  4. ↑ "How Iapetus, Saturn's outermost moon, got its ridge". Retrieved 2010-12-18.
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