The biggest, most sophisticated Mars rover ever built — a car-size vehicle bristling with cameras, microphones, drills and lasers — blasted off Thursday as part of an ambitious, long-range project to bring the first Martian rock samples back to Earth to be analyzed for evidence of ancient life. NASA’s Perseverance rode a mighty Atlas V rocket into the morning sky in the world’s third and final Mars launch of the summer. The plutonium-powered, six-wheeled rover will drill down and collect tiny geological specimens that will be brought home in about 2031 in a sort of interplanetary relay race involving multiple spacecraft and countries.