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Orbit: 238,020 km from Saturn
Orbital period: 33 hours
Gravity: 0.113 m/s²
Diameter: 498 km
Mass: 7.30e19 kg
Enceladus is the sixth-largest of the moons of Saturn. It was discovered in 1789 by William Herschel. Enceladus seems to have liquid water under its icy surface. Cryovolcanoes at the south pole shoot large jets of water ice particles into space.
 Saturn's moon Enceladus

Enceladus has the highest albedo (>0.9) of any body in the solar system. Its surface is dominated by  fresh, clean ice.

At least five different types of terrain have been identified on  Enceladus.  In addition to craters there are smooth plains and extensive linear cracks and ridges. At least some of the surface is relatively young, probably  less than 100  million years.

This means that Enceladus must have been active until very recently  (and perhaps is still active today).  Perhaps some sort of “water volcanism”   is at work.

Enceladus is much too small to be  heated solely by the decay of  radioactive material in its interior at present.  But briefly after its  formation 4.5 billion years ago short-lived radioisotopes may have  provided  enough heat to melt and differentiate the interior.  That combined with modest  present day heating from long-lived isotopes and tidal heating may account for  the present day activity on Enceladus.

Saturn's moon Enceladus, surface shot from Cassini

Cassini closeup view (looks like Europa?)

Enceladus is locked in a 1:2 resonance with Dion (similar to the situation between Io and Europa). This may  provide a heating mechanism but it is probably insufficient to melt water  ice. Enceladus may  therefore be composed of some low-melting point  material rather than  pure water.

Enceladus is very likely the source of the material in Saturn’s tenuous E  ring.  And since the material cannot  persist in the ring for more than a few thousand years, it must be due to  very recent activity on Enceladus.  A less likely possibility is      that the  rings are maintained by high-velocity collisions between dust particles and  the various moons.




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