( Mars ( ( ( looks red ) ( because ( ( its surface ) ( is ( covered ( with ( ( reddish ( iron ( oxide dust ) ) ) ( -LRB- ( rust -RRB- ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NNP Mars)) (VP (VBZ looks) (ADJP (JJ red)) (SBAR (IN because) (S (NP (PRP$ its) (NN surface)) (VP (VBZ is) (VP (VBN covered) (PP (IN with) (NP (NP (JJ reddish) (NN iron) (NN oxide) (NN dust)) (PRN (-LRB- -LRB-) (NP (NN rust)) (-RRB- -RRB-))))))))) (. .)))
Mars looks red because its surface is covered with reddish iron oxide dust (rust).
(ROOT (S (NP (NP (NNP Iron)) (PP (IN in) (NP (DT the) (NN soil)))) (VP (VBZ causes) (S (NP (NNS mars)) (VP (TO to) (VP (VB look) (ADJP (JJ red)))))) (. .)))