NASA is finally ready to snatch at an asteroid. After two years of orbiting the near-Earth asteroid Bennu, as tall as the Empire State Building, NASA's OSIRIS-REx spacecraft will touch down Tuesday in the first US attempt to gather asteroid samples. Over 4.5 hours, the SUV-sized spacecraft will descend from its orbit around the "rubble-pile" asteroid, a collection of rocks held together by gravity some 207 million miles from Earth, using fire thrusters, then extend its robotic arm to collect a sample from the surface, per Space.com. The arm will touch down for no more than 16 seconds in a crater the size of a tennis court, which is surrounded by boulders as large as buildings, reports CNN. It will then fire a pressurized nitrogen canister into the asteroid to lift surface material, up to two kilograms of which will be seized by a collector head at the end of the 11-foot-long arm.
Researchers hope to learn more about how asteroids can impact Earth—Bennu has a one in 2,700 chance of hitting our planet between 2175 and 2199—and how life began. NASA notes this asteroid formed in the first 10 million years of our solar system more than 4.5 billion years ago. "It tells the history of our Earth and solar system," Thomas Zurbuchen, associate administrator of NASA's Science Mission Directorate, said Monday, per CNN. He noted this "historic first mission for NASA" would be "hard." But there's just a 6% chance that OSIRIS-REx will abandon the autonomous mission, based on the team's simulations. If all goes well, the team will have confirmation of a successful touchdown Tuesday night and footage from the spacecraft on Wednesday. The samples are to be sent to Earth next year, with delivery expected in 2023. (Here's what Earth looks like from that far away.)