Concerning the density of small bodies (Prometheus)

[Percebob]

I was looking at the physical properties of some of Saturn's moons and I found that Prometheus was denser in game than planet Earth (IG : Prometheus : 5.66g/cm^3 , Earth : 5.51 g/cm^3 ). Where did you find the data ? Because apparently the error margin is important :"Mass, density and surface gravity all very uncertain" (http://cseligman.com/text/moons/prometheus.htm) Also according to the numbers given by NASA (http://solarsystem.nasa.gov/planets/profile.cfm?Object=Sat_Prometheus) the density should be closer to 0.48g/cm^3. But that's only me doing a quick search, and it's really not that big of a deal, I just wanted to let you know what I found while fiddling around.

[C7]

The mass of bodies is determined by its composition, so a body with more iron will be more dense then one made of lighter materials. This is used to produce a radius for the body, and in turn an average density.

I'll have to check if we've specifically defined a composition for Prometheus or not. But you'll find discrepancies where we've had to more or less "guess" what a body is made out of, when it might not be know in real life. This is often the case for extra-solar bodies and planets.