( ( return ( ( A transit ) ( is ( ( the passing ) ( of ( ( ( a planet ) ( -LRB- ( ( ( Mercury or ) Venus ) -RRB- ) ) ) ( between ( ( ( the Earth ) and ) ( the Sun ) ) ) ) ) ) ) ) ) . )
(ROOT (S (VP (VB return) (SBAR (S (NP (DT A) (NN transit)) (VP (VBZ is) (NP (NP (DT the) (NN passing)) (PP (IN of) (NP (NP (NP (DT a) (NN planet)) (PRN (-LRB- -LRB-) (NP (NNP Mercury) (CC or) (NNP Venus)) (-RRB- -RRB-))) (PP (IN between) (NP (NP (DT the) (NN Earth)) (CC and) (NP (DT the) (NNP Sun))))))))))) (. .)))
return A transit is the passing of a planet (Mercury or Venus) between the Earth and the Sun.
(ROOT (S (NP (NNP Mercury)) (VP (VBZ is) (ADVP (RB always)) (ADJP (ADJP (JJR closer)) (PP (TO to) (NP (DT the) (NN sun)))) (SBAR (IN than) (S (NP (PRP it)) (VP (VBZ is) (PP (TO to) (NP (NN earth))))))) (. .)))
Mercury is always closer to the sun than it is to earth.