Key facts
- Category
- Moons
- Object class
- Co-orbital inner moon
- Composition
- Water ice and rock (rubble pile)
- Temperature
- 76 K surface
Janus
203 kmmaximum extent
203km
Visual creditCassini 2010 / NASA / JPL / Space Science Institute / Public domainSource: Wikimedia Commons
Details
Janus is a cratered inner moon of Saturn that shares almost the same orbit as Epimetheus. Roughly every four years, the two moons exchange momentum and swap which one follows the inner path without ever colliding.
Janus is the larger member of the only known moon pair that repeatedly exchanges neighboring orbits. When it and Epimetheus approach about every four years, mutual gravity moves the inner moon outward and the outer moon inward without a collision. Janus is an oblong, heavily cratered body whose low density suggests a porous aggregate dominated by water ice.
Links
- Universe journey
- Asteroid belt & Jupiter
- Wikipedia
- Janus on Wikipedia
Size neighbors
Objects near Janus on the scale
Shared physical scale
155km
Sources
References for Janus
Measurements and descriptive context are compiled by the Scale of Space team from the references below. If you find an error, write to hello@scaleofspace.org.
- Janus on Wikipedia
- Visual reference: Wikimedia Commons (Cassini 2010 / NASA / JPL / Space Science Institute, Public domain)
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