CAPE CANAVERAL, Fla. — NASA’s Maven spacecraft entered orbit around Mars for an unprecedented study of the red planet’s atmosphere following a 442 million-mile journey that began nearly a year ago.

The robotic explorer successfully slipped into orbit around the red planet late Sunday night.

“I think my heart’s about ready to start again,” Maven’s chief investigator, Bruce Jakosky of the University of Colorado, said early today. “All I can say at this point is, `We’re in orbit at Mars, guys!”’

Now the real work begins for the $671 million mission, the first dedicated to studying the Martian upper atmosphere and the latest step in NASA’s bid to send astronauts to Mars in the 2030s.

Flight controllers in Colorado will spend the next six weeks adjusting Maven’s altitude and checking its science instruments, and observing a comet streaking by at relatively close range. Then in early November, Maven will start probing the upper atmosphere of Mars. The spacecraft will conduct its observations from orbit; it’s not meant to land.

Scientists believe the Martian atmosphere holds clues as to how Earth’s neighbor went from being warm and wet billions of years ago to cold and dry.

NASA launched Maven last November from Cape Canaveral, the 10th U.S. mission sent to orbit the red planet. Three earlier ones failed, and until the official word came of success late Sunday night, the entire team was on edge.

The spacecraft was clocking more than 10,000 mph when it hit the brakes for the so-called orbital insertion, a half-hour process. The world had to wait 12 minutes to learn the outcome, once it occurred, because of the lag in spacecraft signals given the 138 million miles between the two planets Sunday.