( Saturn ( ( is ( ( made mostly ) ( of ( hydrogen ( and ( helium gas ) ) ) ) ) ) . ) )
(ROOT (S (NP (NNP Saturn)) (VP (VBZ is) (VP (VBN made) (ADVP (RB mostly)) (PP (IN of) (NP (NN hydrogen) (CC and) (NN helium) (NN gas))))) (. .)))
Saturn is made mostly of hydrogen and helium gas.
(ROOT (S (NP (NNP Saturn)) (VP (VBZ is) (VP (VBN made) (ADVP (RB mostly)) (PP (IN of) (NP (NN helium) (CC and) (NN hydrogen))))) (. .)))