( ( Although ( Mercury ( is ( ( much closer ) ( to ( the Sun ) ) ) ) ) ) ( , ( Venus ( ( is ( ( the ( hottest planet ) ) ( in ( the ( Solar System ) ) ) ) ) . ) ) ) )
(ROOT (S (SBAR (IN Although) (S (NP (NNP Mercury)) (VP (VBZ is) (ADJP (ADJP (RB much) (JJR closer)) (PP (TO to) (NP (DT the) (NNP Sun))))))) (, ,) (NP (NNP Venus)) (VP (VBZ is) (NP (NP (DT the) (JJS hottest) (NN planet)) (PP (IN in) (NP (DT the) (NNP Solar) (NNP System))))) (. .)))
Although Mercury is much closer to the Sun, Venus is the hottest planet in the Solar System.
(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))))) (. .)))