( ( ( ( ( Mars ( ( is often ) ( referred ( to ( ( ( as ( the ( Red Planet ) ) ) ( because ( ( its ( surface ( ( rocks and ) soil ) ) ) ( are ( colored ( by ( oxidized ( iron minerals ) ) ) ) ) ) ) ) ( -LRB- ( ( ( e.g. , ) rust ) -RRB- ) ) ) ) ) ) ) , ) and ) ( ( dust ( blown ( into ( its ( thin atmosphere ) ) ) ) ) ( ( makes ( its ( sky ( look reddish ) ) ) ) ( as well ) ) ) ) . )
(ROOT (S (S (NP (NNP Mars)) (VP (VBZ is) (ADVP (RB often)) (VP (VBN referred) (PP (TO to) (NP (NP (RB as) (DT the) (JJ Red) (NN Planet)) (SBAR (IN because) (S (NP (PRP$ its) (NN surface) (NNS rocks) (CC and) (NN soil)) (VP (VBP are) (VP (VBN colored) (PP (IN by) (NP (JJ oxidized) (NN iron) (NNS minerals))))))) (PRN (-LRB- -LRB-) (NP (NNP e.g.)) (, ,) (NP (NN rust)) (-RRB- -RRB-))))))) (, ,) (CC and) (S (NP (NP (NN dust)) (VP (VBN blown) (PP (IN into) (NP (PRP$ its) (JJ thin) (NN atmosphere))))) (VP (VBZ makes) (NP (PRP$ its) (NN sky) (NN look) (NN reddish)) (ADVP (RB as) (RB well)))) (. .)))
Mars is often referred to as the Red Planet because its surface rocks and soil are colored by oxidized iron minerals (e.g., rust), and dust blown into its thin atmosphere makes its sky look reddish as well.
(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)))))) (. .)))