( it ( ( is ( filled ( with ( ( very low ) ( density ( ( gas and ) dust ) ) ) ) ) ) . ) )
(ROOT (S (NP (PRP it)) (VP (VBZ is) (VP (VBN filled) (PP (IN with) (NP (ADJP (RB very) (JJ low)) (NN density) (NN gas) (CC and) (NN dust))))) (. .)))
it is filled with very low density gas and dust.
(ROOT (S (NP (NNS Gases)) (VP (VBP have) (NP (DT the) (JJS lowest) (NN density))) (. .)))