Key facts
- Category
- Moons
- Object class
- Co-orbital inner moon
- Composition
- Water ice (porous rubble pile)
- Temperature
- 78 K surface
Epimetheus
130 kmmaximum extent
Explore Epimetheus to scaleVisual creditCassini 2007 / NASA / JPL / Space Science Institute / Public domainSource: Wikimedia Commons
Details
Epimetheus is a porous, cratered inner moon of Saturn that shares two neighboring orbits with Janus. About every four years, the pair exchange momentum and swap which moon follows the inner path.
Epimetheus and Janus follow orbits separated by only about 50 kilometers. Roughly every four years the inner, faster moon catches the outer one; their gravitational interaction transfers momentum, and each moves onto the other path while they remain about 15,000 kilometers apart at closest approach. Voyager 1 confirmed in 1980 that the conflicting earlier observations belonged to two moons, not one.
Cassini images show Epimetheus as an irregular, cratered body with a flattened south-polar region. Its low density supports a porous, ice-rich structure, while dust knocked from Epimetheus and Janus may supply the faint ring along their shared orbit.
Links
- Wikipedia
- Epimetheus on Wikipedia
Size neighbors
Objects near Epimetheus on the scale
On the logarithmic size axis, Epimetheus falls between 21 Lutetia and Prometheus. The band uses nearby Co-orbital inner moon records.
Shared physical scale
155km
Sources
References for Epimetheus
Measurements and descriptive context are compiled by the Scale of Space team from the references below. If you find an error, please let us know.
- Epimetheus — Wikipedia
- Visual reference: Wikimedia Commons (Cassini 2007 / NASA / JPL / Space Science Institute, Public domain)
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About
Scale of Space is a scroll-based journey through the universe, placing objects on a single logarithmic scale so you can compare size across an unbroken range.
Guides explain selected parts of that range, while focused views filter the objects by subject.