( ( ( Earth 's ) atmosphere ) ( ( consists ( of ( ( ( mainly oxygen ) and ) nitrogen ) ) ) . ) )
(ROOT (S (NP (NP (NNP Earth) (POS 's)) (NN atmosphere)) (VP (VBZ consists) (PP (IN of) (NP (NP (RB mainly) (NN oxygen)) (CC and) (NP (NN nitrogen))))) (. .)))
Earth's atmosphere consists of mainly oxygen and nitrogen.
(ROOT (S (NP (NN Oxygen) (CC and) (NN nitrogen)) (VP (VBP make) (PRT (RP up)) (NP (NP (JJS most)) (PP (IN of) (NP (NP (DT the) (NN earth) (POS 's)) (NN atmosphere))))) (. .)))
Oxygen and nitrogen make up most of the earth's atmosphere.