Jul 6, 2003 - NASA has pushed back the launch of its second Mars Exploration rover, "Opportunity", again; this time because of a battery failure on the Boeing Delta II booster. The launch has now been set for Tuesday, July 8 at 0235 GMT (10:35 pm EDT Monday). Even this launch date is at risk, though, as there's a 30% chance of weather problems. It looks like the previous problem with the booster's cork insulation has been resolved; although, engineers will be performing further tests to ensure that everything's fine. The spacecraft must launch before July 15 in order to reach Mars.