( Mercury ( ( is ( by ( ( ( far ( the densest ) ) ( ( ( of ( ( the planets ) ( in ( the ( solar system ) ) ) ) ) , ) ( ( a fact ) that ) ) ) ( puzzles scientists ) ) ) ) . ) )
(ROOT (S (NP (NNP Mercury)) (VP (VBZ is) (PP (IN by) (NP (ADVP (RB far) (NP (DT the) (NN densest)) (PP (IN of) (NP (NP (DT the) (NNS planets)) (PP (IN in) (NP (DT the) (JJ solar) (NN system)))) (, ,) (ADVP (NP (DT a) (NN fact)) (IN that)))) (CD puzzles) (NNS scientists)))) (. .)))
Mercury is by far the densest of the planets in the solar system, a fact that puzzles scientists.
(ROOT (S (NP (NNP Mercury)) (VP (VBZ is) (NP (NP (DT the) (JJS smallest) (NN planet)) (PP (IN in) (NP (PRP$ our) (JJ solar) (NN system))))) (. .)))