( ( ( Space-based observations ) ( of ( comets ( Cometary scientists ) ) ) ) ( ( all ( over ( the world ) ) ) ( ( are ( ( following ( ( the preparation ) ( of ( space missions ) ) ) ) ( to ( comets ( with ( great interest ) ) ) ) ) ) . ) ) )
(ROOT (S (NP (NP (JJ Space-based) (NNS observations)) (PP (IN of) (NP (NNP comets) (NNP Cometary) (NNS scientists)))) (ADVP (DT all) (PP (IN over) (NP (DT the) (NN world)))) (VP (VBP are) (VP (VBG following) (NP (NP (DT the) (NN preparation)) (PP (IN of) (NP (NN space) (NNS missions)))) (PP (TO to) (NP (NP (NNS comets)) (PP (IN with) (NP (JJ great) (NN interest))))))) (. .)))
Space-based observations of comets Cometary scientists all over the world are following the preparation of space missions to comets with great interest.
(ROOT (S (NP (NNS Scientists)) (VP (VBP explain) (NP (DT the) (NN world)) (PP (VBN based) (PP (IN on) (NP (NNS observations))))) (. .)))