Before Matt Heverly could begin his daily task of guiding the Curiosity rover across Mars, the $2.5 billion robot had to land on the planet's surface.

Before Matt Heverly could begin his daily task of guiding the Curiosity rover across Mars, the $2.5 billion robot had to land on the planet's surface.

That meant going from its atmospheric entry speed of 13,000 mph to a standstill — in just seven minutes.

Seven minutes of terror.

"I didn't even really allow myself to think about what if it didn't land successfully," Heverly says.

Surrounded by colleagues, family and strangers, Heverly watched the action on a Jumbotron television at Caltech, one of countless such gatherings as the world awaited Curiosity's historic touchdown on Aug. 5, 2012.

"There were hundreds of people," Heverly says. "It was just, I mean, it was amazing. It was gut-wrenching to think about what was happening."

He'd already watched the launch in Florida with his wife and 4-year-old son, Paxton. Now, about nine months later, Curiosity had reached its destination.

The robot's landing sequence was a complicated one. As laid out in the video "Seven Minutes of Terror: Curiosity Rover's Risky Mars Landing," there was zero room for error.

"If any one thing doesn't work just right, it's game over," Curiosity engineer Tom Rivellini says in the video.

When the robot's space capsule entered Mars' thin atmosphere — one-hundreth the thickness of Earth's — the craft's heat shield glowed bright red at 1,600 degrees from the friction. But it slowed Curiosity's decent only to about 1,000 mph, not nearly enough to avoid a mission-ending collision with the surface.

A supersonic parachute erupted from the craft's top shortly after entry, billowing out and yanking up the spacecraft, reducing its speed to 200 mph.

The heat shield dropped off. Then Curiosity dropped from the vessel, attached to several rockets that fired and slowed its speed even further. Using radar, it drifted down to its landing site, near the base of Mount Sharp, a rust-colored peak that's almost as high as Earth's Mount McKinley.

The last step came 20 meters above the ground. Descending to the surface using the rockets alone would send up a cloud of sand and rocks that could damage Curiosity's sensitive instruments. Instead, a crane attached to the rockets lowered Curiosity the final 20 meters before the rocket craft separated and launched into the sky toward a planned crash miles away.

Heverly and the other viewers watched it all on a 14-minute delay, as the signals had to travel through space back to Earth. For better or worse, the landing would be long over by the time word reached NASA.

"My emotional investment was tremendously high," Heverly says. "I don't get to do my job unless that part of the mission works."

Then came the news over the Jumbotron speakers: "Touchdown confirmed. We're safe on Mars." It was 10:32 p.m., PST.

Cheers erupted around Heverly. Some wept. Soon after, Curiosity transmitted its first image. It showed Mount Sharp and the robot's shadow, the flat expanse of nothing in between.

"It was one of those things where you collectively have this big sigh, and then you have to start doing it for real," Heverly says.