( ( The planet ) ( ( ( ( ( ( ( rotates on ) ( its axis ) ) ( very slowly ) ) , ) once ) ( in ( 59 ( Earth days ) ) ) ) . ) )
(ROOT (S (NP (DT The) (NN planet)) (VP (VBZ rotates) (PRT (RP on)) (NP (PRP$ its) (NNS axis)) (ADVP (RB very) (RB slowly)) (, ,) (ADVP (RB once)) (PP (IN in) (NP (CD 59) (NNP Earth) (NNS days)))) (. .)))
The planet rotates on its axis very slowly , once in 59 Earth days.
(ROOT (S (NP (NNP Earth)) (VP (VBZ rotates) (PP (PP (IN on) (NP (PRP$ its) (NNS axis)) (ADVP (RB once))) (CC times) (PP (IN in) (NP (CD one) (NN day))))) (. .)))