PX282 - K5 - moons

jupiter

image: Galileo probe, NASA/JPL/DLR

four large galilean moons*, with many smaller, non-spherical moons, probably mostly captured asteroids
density decreases with separation from jupiter, as the volatile content (ices) increases
this is likely due to temperature gradients in the disc surrounding jupiter during the formation of the moons
also, tidal heating evaporates volatiles (due to resonant orbits of the moons)
io is rocky and volcanic, with a very young surface
europa has a rocky core, and a young icy surface as it is resurfaced by liquid water from tidally heated subsurface ocean
ganymede and callisto have masses dominated by ice, with older cratered surfaces, with some cracks due to geological activity (water ice, rather than rock)

seven spherical moons, with one very large moon, titan
titan has a thick $1.5$ bar N $_{2}$ atmosphere with photochemical hydrocarbon haze
radar imaging with huygens probe show liquid methane rivers and lakes
enceladus, a relatively small moon, which orbits relatively close to satrun
due to tidal heating, it has oceans of liquid water below a thin ice crust

at least 27 moons, with five approximately spherical ones with similar composition/density trends to the galilean moons
they are aligned with the $98 °$ spin obliquity of the planet, suggesting that the moon system formed from the debris disc from the giant collision that caused the tilt

at least fourteen moons, with one spherical, triton
it is probably a dwarf planet, captured from the kuiper belt as it has a retrograde orbit
it may have destabilized the primordial moon system of neptune

made up of ice particles of sizes: $\sim 0.01 - 1$ m
they have a complex structure due to orbital resonances with saturn's moons
it is extremely thin due to collisions when any particle orbits out of the disc plane, and have disc crossing orbits
the main rings extend from $\sim 1.2 - 2.3 R_{p}$
the roche limit:

a_{R} = 2.456 {(\frac{ρ_{p}}{ρ_{m}})}^{1 / 3} R_{p}

for saturn, $ρ_{p} = 700$ kg m $^{- 3}$ , and assuming that $ρ_{m} ≃ 1000$ kg m $^{- 3}$ (icy moon)

a_{R} = 2.2 R_{p}

this aligns with the outer extent of the rings
so, this implies that the rings were probably a tidally disrupted icy moon that migrated in to its roche limit, maybe due to tidal synchronization
there is also a dusty, 'E' ring, association with ejection from enceladus