( ( ( ( Mars , ) ( ( the ( fourth planet ) ) ( from ( the sun ) ) ) ) , ) ( ( ( has long ) ( ( been ( ( a subject ) ( of ( intense ( scientific interest ) ) ) ) ) ( as ( one ( of ( ( the ( most ( Earthlike planets ) ) ) ( in ( our ( solar system ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NP (NNP Mars)) (, ,) (NP (NP (DT the) (JJ fourth) (NN planet)) (PP (IN from) (NP (DT the) (NN sun)))) (, ,)) (VP (VBZ has) (ADVP (RB long)) (VP (VBN been) (NP (NP (DT a) (NN subject)) (PP (IN of) (NP (JJ intense) (JJ scientific) (NN interest)))) (PP (IN as) (NP (NP (CD one)) (PP (IN of) (NP (NP (DT the) (RBS most) (JJ Earthlike) (NNS planets)) (PP (IN in) (NP (PRP$ our) (JJ solar) (NN system))))))))) (. .)))
Mars, the fourth planet from the sun, has long been a subject of intense scientific interest as one of the most Earthlike planets in our solar system.
(ROOT (S (NP (NNP Mars)) (VP (VBZ is) (NP (NP (DT the) (JJ fourth) (NN planet)) (PP (IN from) (NP (DT the) (NN sun))))) (. .)))