Efforts to explore Mars – a planet that has captivated the human imagination for millenniums – represent one of the few bright spots in a space program overshadowed by the loss of the shuttle Columbia and its crew last month. Now, US and European scientists are poised for a return to the red planet late this spring in an unprecedented effort to deliver two rovers and a lander to the surface, while a new orbiter takes up station high above to gather stereo images of the planet’s surface in extraordinary detail. The projects, NASA’s Mars Exploration Rover mission and the European Space Agency’s Mars Express, will help determine whether Mars could once have hosted simple forms of organic life – and whether such forms still may exist there.