 Although close to Jupiter , New Horizons ' instruments made refined measurements of the orbits of Jupiter 's inner moons , particularly Amalthea . The probe 's cameras measured volcanoes on Io , studied all four Galilean moons in detail , and made long @-@ distance studies of the outer moons <unk> and <unk> . The craft also studied Jupiter 's Little Red Spot and the planet 's magnetosphere and tenuous ring system . 
