When two NASA rovers explore the surface of Mars in early 2004, 16 students will have a front-row seat in mission control to watch the action. They will be the winners of an essay contest, called the Red Rover Goes to Mars project, sponsored by NASA, the Planetary Society and the LEGO toy company. Organizers announced the start of the contest, open to students age 12 to 16, Tuesday at the World Space Congress. Students who write the best essays — outlining how the student would deploy a rover on Mars — will receive a free trip to Pasadena, Calif., to spend one week at NASA’s Jet Propulsion Laboratory, which controls the rovers.