( ( As ( ( the comet ) passed ) ) ( , ( it ( ( left ( behind ( ( a trail ) ( of ( ( dust and ) particles ) ) ) ) ) . ) ) ) )
(ROOT (S (SBAR (IN As) (S (NP (DT the) (NN comet)) (VP (VBD passed)))) (, ,) (NP (PRP it)) (VP (VBD left) (PP (IN behind) (NP (NP (DT a) (NN trail)) (PP (IN of) (NP (NN dust) (CC and) (NNS particles)))))) (. .)))
As the comet passed, it left behind a trail of dust and particles.
(ROOT (S (NP (JJ Comet) (NNS tails)) (VP (ADVP (RB always)) (VBP point) (PRT (RP away)) (PP (IN from) (NP (NP (DT the) (NN sun)) (PP (RB instead) (IN of) (S (VP (VBG trailing) (PP (IN behind) (NP (DT the) (ADJP (JJ comet) (PP (IN because) (NP (NN dust) (NNS particles)))) (NN recoil))))))))) (. .)))