CAPE CANAVERAL, Fla. (AP) — NASA's Maven spacecraft arrived at Mars late Sunday after a 442 million-mile journey that began nearly a year ago. The robotic explorer fired its brakes and successfully slipped into orbit around the red planet, officials confirmed. "This is such an incredible night," said John Grunsfeld, NASA's chief for science missions. Now the real work begins for the $671 million mission, the first dedicated to studying Mars' upper atmosphere. Flight controllers in Colorado will spend the next six weeks adjusting Maven's altitude and checking its science instruments.