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