A NASA rover streaked through the orange Martian sky and landed on the planet Thursday, accomplishing the riskiest step yet in an epic quest to bring back rocks that could answer whether life ever existed on Mars.

Ground controllers at the space agency’s Jet Propulsion Laboratory in Pasadena, California, leaped to their feet, thrust their arms in the air and cheered in both triumph and relief on receiving confirmation that the six-wheeled Perseverance had touched down on the red planet, long a deathtrap for incoming spacecraft.

“Now the amazing science starts,” a jubilant Thomas Zurbuchen, NASA’s science mission chief, said at a news conference, where he theatrically ripped up the contingency plan in the event of a failure and threw the document over his shoulders.

The landing marks the third visit to Mars in just over a week. Two spacecraft from the United Arab Emirates and China swung into orbit around Mars on successive days last week. All three missions lifted off in July to take advantage of the close alignment of Earth and Mars, journeying some 300 million miles in nearly seven months.

Perseverance, the biggest, most advanced rover ever sent by NASA, became the ninth spacecraft since the 1970s to successfully land on Mars, every one of them from the U.S.

The car-size, plutonium-powered vehicle arrived at Jezero Crater, hitting NASA’s smallest and trickiest target yet: a 5-by-4-mile strip on an ancient river delta full of pits, cliffs and rocks. Scientists believe that if life ever flourished on Mars, it would have happened 3 billion to 4 billion years ago, when water still flowed on the planet.

Over the next two years, Percy, as it is nicknamed, will use its 7-foot (2-meter) arm to drill down and collect rock samples containing possible signs of bygone microscopic life. Three to four dozen chalk-size samples will be sealed in tubes and set aside to be retrieved eventually by another rover and brought homeward by another rocket ship.

The goal is to get them back to Earth as early as 2031.