( ( ( The ( main gas ) ) ( in Earth ) ) ( ( 's ( atmosphere 7 ) ) . ) )
(ROOT (S (NP (NP (DT The) (JJ main) (NN gas)) (PP (IN in) (NP (NNP Earth)))) (VP (VBZ 's) (NP (NN atmosphere) (CD 7))) (. .)))
The main gas in Earth's atmosphere 7.
(ROOT (S (NP (JJ Volcanic) (NNS gases)) (VP (VBP helpe) (S (VP (TO to) (VP (VB form) (NP (DT the) (NN atmosphere)) (PP (IN on) (NP (NN earth))))))) (. .)))