(S (S (NP (DT The) (NP (NP (BASENP (NNP Ion)) (CC and) (BASENP (NNP Neutral) (NNP Mass))) (NNP Spectrometer))) (VP (VBD saw) (NP (NP (BASENP (DT a) (ADJP (RB much) (JJR higher)) (NN density)) (PP (IN of) (NP (NP (NP (NP (BASENP (JJ volatile) (NNS gases)) (COMMA ,) (BASENP (NN water) (NN vapor))) (COMMA ,) (BASENP (NN carbon) (NN dioxide))) (CC and) (BASENP (NN carbon) (NN monoxide))) (CONJP (COMMA ,) (CONJP (ADVP (RB as) (RB well)) (IN as))) (BASENP (JJ organic) (NNS materials))))) (COMMA ,) (ADJP (ADJP (QP (QP (DT some) (NN 20)) (NNS times)) (JJR denser)) (SBAR (IN than) (S (VP (VBN expected)))))))) (PERIOD .))