CAPE CANAVERAL, Fla. — After almost two years circling an ancient asteroid hundreds of millions of miles away, a NASA spacecraft this week will attempt to descend to the treacherous, boulder-packed surface and snatch a handful of rubble.

The drama unfolds Tuesday as the United States takes its first crack at collecting asteroid samples for return to Earth, a feat accomplished so far only by Japan.

Brimming with names inspired by Egyptian mythology, the Osiris-Rex mission is looking to bring back at least 2 ounces worth of asteroid Bennu, the biggest otherworldly haul from beyond the moon.

The van-sized spacecraft is aiming for the relatively flat middle of a tennis court-sized crater named Nightingale — a spot comparable to a few parking places here on Earth. Boulders as big as buildings loom over the targeted touchdown zone.

“So for some perspective, the next time you park your car in front of your house or in front of a coffee shop and walk inside, think about the challenge of navigating Osiris-Rex into one of these spots from 200 million miles away,’’ said NASA’s deputy project manager Mike Moreau.

Once it drops out of its half-mile-high orbit around Bennu, the spacecraft will take a deliberate four hours to make it all the way down, to just above the surface.

Then the action cranks up when Osiris-Rex’s 11-foot arm reaches out and touches Bennu. Contact should last five to 10 seconds, just long enough to shoot out pressurized nitrogen gas and suck up the churned dirt and gravel. Programmed in advance, the spacecraft will operate autonomously during the unprecedented touch-and-go maneuver. With an 18-minute lag in radio communication each way, ground controllers can't intervene.

If the first attempt doesn't work, Osiris-Rex can try again. Any collected samples won’t reach Earth until 2023.

While NASA has brought back comet dust and solar wind particles, it’s never attempted to sample one of the nearly 1 million known asteroids lurking in our solar system until now.

ASSOCIATED PRESS