(S (S (S (NP (BASENP (DT This) (JJ dramatic) (NN increase)) (PP (IN in) (BASENP (NN density)))) (VP (VBD was) (ADJP (JJ evident)))) (SBAR (IN as) (S (BASENP (DT the) (NN spacecraft)) (VP (VBD flew) (PP (IN over) (NP (BASENP (DT the) (NN area)) (PP (IN of) (BASENP (DT the) (NNS plumes))))))))) (PERIOD .))