Scientists preparing for NASA’s next Mars mission, the twin Mars Exploration Rovers scheduled for launch in June and July 2003, are able to view more than 44,000 high-resolution images of Mars collected by the Mars Global Surveyor. Some show detail at less than three meters per pixel. These images are registered with context images and maps of thermal properties, rock abundance, slope roughness and geology acquired by the Viking and Global Surveyor orbiters and with altimeter and mineralogical data returned by Global Surveyor, which is still operating at Mars. The Web site provides scientists with special software tools to facilitate their interpretation of the data.