( ( ( Roughly 1 ) ( per ( cent ( of ( the ( interstellar medium ) ) ) ) ) ) ( is ( ( dust , ) ( ( the ( rest ( hydrogen gas ) ) ) ( -LRB- 80 ) ) ) ) )
(ROOT (S (NP (NP (QP (RB Roughly) (CD 1))) (PP (IN per) (NP (NP (NN cent)) (PP (IN of) (NP (DT the) (NN interstellar) (NN medium)))))) (VP (VBZ is) (NP (NP (NN dust)) (, ,) (NP (NP (DT the) (NN rest) (NN hydrogen) (NN gas)) (NP (QP (CD -LRB-) (CD 80))))))))
Roughly 1 per cent of the interstellar medium is dust, the rest hydrogen gas (80
(ROOT (S (NP (JJ Interstellar) (NN medium)) (VP (VBZ consists) (PP (IN of) (NP (NP (RB thinly) (NN spread) (NN gas)) (CC and) (NP (NN dust))))) (. .)))