( ( ( ( ( ( The ( Martian day ) ) , ) or ) ( ( the time ) ( it ( takes ( Mars ( to ( ( rotate once ) ( on ( its axis ) ) ) ) ) ) ) ) ) , ) ( ( is ( ( ( ( about ( a half ) ) ( an hour ) ) longer ) ( than ( an ( Earth day ) ) ) ) ) . ) )
(ROOT (S (NP (NP (DT The) (JJ Martian) (NN day)) (, ,) (CC or) (NP (NP (DT the) (NN time)) (SBAR (S (NP (PRP it)) (VP (VBZ takes) (S (NP (NNP Mars)) (VP (TO to) (VP (VB rotate) (ADVP (RB once)) (PP (IN on) (NP (PRP$ its) (NNS axis)))))))))) (, ,)) (VP (VBZ is) (ADJP (ADJP (NP (NP (QP (RB about) (DT a) (NN half))) (NP (DT an) (NN hour))) (JJR longer)) (PP (IN than) (NP (DT an) (NNP Earth) (NN day))))) (. .)))
The Martian day, or the time it takes Mars to rotate once on its axis, is about a half an hour longer than an Earth day.
(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))))) (. .)))