CAPE CANAVERAL -- All eyes here are on shuttle Discovery's scheduled landing this morning, but in reality NASA considers the fleet of shuttles to be outmoded flying cargo trucks soon destined for mothballs. The agency is increasingly turning its full focus to the goal that truly drives it: placing humans on Mars. This week the National Aeronautics and Space Administration plans to launch the Mars Reconnaissance Orbiter, an unmanned satellite-like probe that will study the red planet for signs of past life and of existing water supplies -- as well as potential landing spots for manned missions. Meanwhile, NASA officials...