( ( ( Saturn 's ) atmosphere ) ( ( is ( ( ( ( composed mainly ) ( of ( ( hydrogen and ) helium ) ) ) , ) ( ( ( the ( same gases ) ) out ) ( ( of which ) ( ( ( ( the Sun ) and ) ( most stars ) ) ( are made ) ) ) ) ) ) . ) )
(ROOT (S (NP (NP (NNP Saturn) (POS 's)) (NN atmosphere)) (VP (VBZ is) (VP (VBN composed) (ADVP (RB mainly)) (PP (IN of) (NP (NN hydrogen) (CC and) (NN helium))) (, ,) (ADVP (ADVP (NP (DT the) (JJ same) (NNS gases)) (IN out)) (SBAR (WHPP (IN of) (WHNP (WDT which))) (S (NP (NP (DT the) (NNP Sun)) (CC and) (NP (JJS most) (NNS stars))) (VP (VBP are) (VP (VBN made)))))))) (. .)))
Saturn's atmosphere is composed mainly of hydrogen and helium, the same gases out of which the Sun and most stars are made.
(ROOT (S (NP (NNP Saturn)) (VP (VBZ is) (VP (VBN made) (ADVP (RB mostly)) (PP (IN of) (NP (NN helium) (CC and) (NN hydrogen))))) (. .)))