( Mercury ( ( is ( ( the ( closet planet ) ) ( to ( the sun ) ) ) ) . ) )
(ROOT (S (NP (NNP Mercury)) (VP (VBZ is) (NP (NP (DT the) (NN closet) (NN planet)) (PP (TO to) (NP (DT the) (NN sun))))) (. .)))
Mercury is the closet planet to the sun.
(ROOT (S (NP (NNP Mercury)) (VP (VBZ is) (ADJP (ADJP (JJS closest)) (PP (TO to) (NP (PRP$ our) (NN sun))))) (. .)))