Chapter 9, Problem 25TYU

The moons of Saturn may have large amounts of ammonia and methane ice, while those of Jupiter do not because (a) methane and ammonia come only from comets that exist in the Oort cloud; (b) Jupiter’s strong magnetic field encourages water ice to form; (c) the greater cold at Saturn’s distance from the Sun means that ices of ammonia and methane could condense there but not at Jupiter.