about 10 seconds with google came up with this article.
https://phys.org/news/2015-09-moons-neptune.html
It lists the moons, along with their sizes and masses, so if you want, you can calculate their density and compare it with known rocky/icy densities.
But even without doing that, it is likely that the moons are not rocky, but rather icy. Uranus and Neptune are ice giants, with large deep atmospheres. So they have solid surfaces. But the whole region of the solar system out beyond Neptune is mainly ice worlds. Some may have rocky cores, but most of the solid stuff that far out is what we would normally consider gases, but frozen solid. The heavier elements (what we consider rocks on earth) are almost all in the inner solar system.
Which one of neptune's moons are solid rock or ground?
1 answer