TheattempttosendandlandastronautsonMarsrisksbillionsofdollarsandthelivesofthosebraveenoughtoattemptit.Isthepossiblebenefitreallyworththerisk?Andisitreallyachievable?　　GuidingusthroughthisethicalandscientificminefieldisDrKevinFong.Kevin'sdiversebackgroundinastrophysics,aeronauticsandmedicinemakeshimuniquelyplacedtounders..aaa