The next U.S. Mars landing attempt will be a pair of long-range “Mars Exploration Rovers” scheduled for launch on May 30 and June 27, 2003 — which will land on Mars on Jan. 4 and Feb. 8, 2004, using the Martian beachball technique that was so successful in the 1996 Mars Pathfinder mission. After each Pathfinder-based lander rolls to a stop and props itself upright by unfolding three side petals, the 150-kg rover nestled between them will scan its surroundings, and shortly afterwards roll away on a voyage of discovery that will last three to six months and stretch a kilometer or more across the surface.