( ( ( Saturn ( Saturn 's ) ) atmosphere ) ( ( ( is ( almost entirely ) ) ( ( hydrogen and ) helium ) ) . ) )
(ROOT (S (NP (NP (NNP Saturn) (NNP Saturn) (POS 's)) (NN atmosphere)) (VP (VBZ is) (ADVP (RB almost) (RB entirely)) (NP (NP (NN hydrogen)) (CC and) (NP (NNP helium)))) (. .)))
Saturn Saturn's atmosphere is almost entirely hydrogen and helium.
(ROOT (S (NP (NNP Saturn)) (VP (VBZ is) (VP (VBN made) (ADVP (RB mostly)) (PP (IN of) (NP (NN helium) (CC and) (NN hydrogen))))) (. .)))