Amalthea And Company Options

[tedstryk]

I had a thought. Is it possible that there was once a fifth large moon in the Jovian system - maybe not another Galilean, but at least a Rhea or Enceladus? And perhaps it was ripped apart by a collison with a kuiperoid in Jovian orbit. The pieces of it, mixed with the fragments of the impactor, may have never been able to reassemble given the tidal environment, but instead formed the rings and the little group of inner moons. If the kuiperoid was much larger than the satellite it hit - but coming at a high enough relative speed to be shattered anyway, that would explain the lack of rocky materials. Any thoughts on this?

[Guest_BruceMoomaw_*]

By the way, the original theory was that Amalthea's low density was due to the fact that it was a loose, gravitationally clumped "rubble pile" -- which, in retrospect, is perfectly logical given the number of impacts it's undergone from infalling meteoroids. (Galileo's star sensor confirmed that some fairly large objects are being knocked off it right now and orbiting immediately nearby.)

However, the final figure for its density has turned out to be so low that it must be both a rubble pile AND largely icy -- just as with all of Saturn's moons closer than Mimas.