Small Moons - Aberrant gravity?

<i>Originally posted by Jeremy</i>
<br />If it were a rubble pile, it would probably be denser than it is. Such low densities suggest light materials, huge fissures, or bubbles in the interior. But it is legitimate to wonder about the accuracy of the mass estimates. The tug of these small moons on passing spacecraft is minumal and hard to measure. -|Tom|-

In the case of Amalthea it is my understanding that the measurement was fairly accurate as the probe made a very close flyby. Unfortunately we got no good images in the last passby that would have confirmed or denied the rubble pile theory. So far we haven't seen any sizeable fissures. I suppose interior bubbles are possible but how could we find them without drilling? My feeling is that these moons are chunks of rock with a coating of ice. Too bad we don't have a Deep Impact probe out there to get some more information.

JPL.NASA has the density of this moon posted as 1.8g/cc which is dense enough to be a solid moon it seems to me. What is your figure for the density? Or is this too low a density for some reason?

John Anderson originally announced that it was close to water-ice in density. If it is indeed 1.8 then I guess it is not that low.