Ground controllers in the space agency’s Jet Propulsion Laboratory at Pasadena, California, settled in nervously for the descent of Perseverance to the surface of Mars, long a deathtrap for incoming spacecraft. It takes a nail-biting 11 1/2 minutes to get a sign that would confirm success to reach Earth.

The landing of the six-wheeled automobile would indicate the third visit to Mars in just over a week. Two spacecraft in the United Arab Emirates and China swung into orbit around the planet on consecutive days each week.

All three missions lifted off in July to take advantage of this close proximity of Earth and Mars, travel some 300 million kilometers in almost seven months.

Perseverance, the biggest, most innovative rover ever sent by NASA, stood to become the ninth largest spacecraft to successfully land on Mars, every one of them by the U.S., starting in the 1970s.

The car-size, plutonium-powered rover was aiming for NASA’s tiniest and trickiest goal yet: a 5–by-4-mile strip on an ancient river delta filled with pits, cliffs and areas of rock. Scientists think that if life ever flourished on Mars, it would have happened 3 billion to 4 billion decades ago, when water still flowed on the planet.

Percy, as it’s nicknamed, was created to drill down with its 7-foot (2-meter) arm and collect rock samples that might hold signs of bygone microscopic life. The plan required three to four dozen chalk-size samples to be sealed in capsules and set aside on Mars to be recovered by a fetch rover and brought homeward by another enemy boat, with the goal of getting them back to Earth as ancient as 2031.

Scientists expect to answer a few of the central concerns of theology, philosophy and space exploration.

“Are we alone in this sort of vast cosmic desert, just flying through space, or is life considerably more common? Does this just emerge whenever and wherever the conditions are ripe?” Stated deputy project scientist Ken Willifordsaid “Big, fundamental questions, and we do not understand the answers yet. So we’re really on the verge of being able to possibly answer these questions that are enormous.”

China’s spacecraft includes a smaller rover that also is searching for evidence of life — even if it makes it safely down from orbit in May or June.

Perseverance’s descent was clarified by NASA as”seven minutes of dread,” in which flight controls can only watch helplessly. The preprogrammed spacecraft was created to hit the thin Martian atmosphere at 12,100 miles (19,500 kph), then use a parachute to slow down it and also a rocket-steered platform called a sky crane to reduce the rover the rest of the way into the surface.

Mars has established a dangerous place: In the course of less than three months in 1999, a U.S. spacecraft was destroyed upon entering orbit since engineers had mixed up metric and English units, and an American lander crashed on Mars after its engines cut prematurely.

Perseverance’s mission costs nearly $3 billion.

The only real way to confirm — or rule out — indications of past life is to examine the samples from the world’s greatest labs. Instruments little enough to be sent to Mars would not have the necessary precision.

“The Mars sample return job is most likely the most challenging thing we’ve ever tried within NASA,” said planetary science manager Lori Glaze,”and we do not do any of these things alone.”