To stay alive five years on Mars, you have to have a nose for trouble. You have to be able to smell it before it happens, to catch the oderiferous tang of it in the dry wind blowing across the red deserts, to sense it in the shifting shadows of the sunset. Otherwise you may not stay alive on Mars for five months let alone five years. Or for five days, if you happen to be in the wrong place. Boyd Larkin had lived seven years on Mars, in the wrongest of all wrong places on the red planet, the city