After several delays the last couple of weeks due to problems with the Boeing Delta II launch vehicle the Mars Exploration Rover (MER-B) Opportunity successfully lifted off for Mars today at 11:18:15 p.m. EDT (0318:15 GMT). The evening launch did not go off without problems though. The first launch attempt was aborted at T-minus 7 seconds because of a glitch with the fill and drain valve. However a go was given minutes later and the countdown resumed at T-minus 4 minutes.
On June 10 the first of the Twin Rovers, Spirit, was successfully launched towards Mars. Opportunity is scheduled to arrive at Mars on January 25, 2004 three weeks after Spirit. Already in orbit should be the European Space Agency's Mars Express which is scheduled to arrive December 25 and the Beagle 2 lander should be on Mars.
The two Mars Exploration rovers will be seek to determine the history of climate and water at two sites on Mars where conditions may once have been favorable to life. Each rover carries five scientific instruments including a panoramic camera and microscope, plus a rock abrasion tool that will grind away the outer surfaces of rocks to expose their interiors for examination. The rovers will navigate themselves around obstacles as they drive across the Martian surface, traveling up to about 130 feet each day. Each rover's prime mission is planned to last three months on Mars.