( ( ( ( ( Astronomers ( have ( ( ( detected them ) ( in ( dense clouds ) ) ) ( since ( the ( 1960 's ) ) ) ) ) ) , ) and ) ( ( by ( carefully ( examining ( carbonaceous ( chrondritic meteorites ) ) ) ) ) ( , ( we ( ( know ( them ( to ( be ( part ( of ( ( the material ) ( of ( the ( early ( ` ( solar nebula ) ) ) ) ) ) ) ) ) ) ) ) ' ) ) ) ) ) . )
(ROOT (S (S (NP (NNS Astronomers)) (VP (VBP have) (VP (VBN detected) (NP (PRP them)) (PP (IN in) (NP (JJ dense) (NNS clouds))) (PP (IN since) (NP (DT the) (CD 1960) (NNS 's)))))) (, ,) (CC and) (S (PP (IN by) (S (ADVP (RB carefully)) (VP (VBG examining) (NP (JJ carbonaceous) (JJ chrondritic) (NNS meteorites))))) (, ,) (NP (PRP we)) (VP (VBP know) (S (NP (PRP them)) (VP (TO to) (VP (VB be) (NP (NP (NN part)) (PP (IN of) (NP (NP (DT the) (NN material)) (PP (IN of) (NP (DT the) (JJ early) (`` `) (JJ solar) (NN nebula)))))))))) ('' ')) (. .)))
Astronomers have detected them in dense clouds since the 1960's, and by carefully examining carbonaceous chrondritic meteorites, we know them to be part of the material of the early 'solar nebula'.
(ROOT (S (NP (NNS Meteorites)) (VP (VBP are) (ADVP (RB often)) (VP (VBN comprised) (PP (IN of) (NP (NP (NNS remnants)) (PP (IN of) (NP (NP (DT the) (JJS earliest) (NN material)) (SBAR (WHNP (WDT that)) (S (VP (VBN formed) (PP (IN in) (NP (DT the) (JJ solar) (NN system)))))))))))) (. .)))