U.S. begins groundbreaking asteroid descent

Some 200 million miles from Earth, between Mars and Jupiter, a NASA spacecraft began slowly approaching the surface of Bennu on Tuesday. The Osiris-Rex takes 4½ hours to reach the surface to complete its mission, the United States’ first attempt to gather samples from an asteroid as it careens through space.

What’s the goal? The spacecraft will pull up next to Bennu, spew pressurized nitrogen gas at the surface to stir up materials, and try to capture 2 ounces of loose pebbles or dust. The difficult part is getting close enough. At only 1,670 feet across, Bennu doesn’t generate enough gravity for Osiris-Rex to land. The van-sized spacecraft will hover near the asteroid and reach out an 11-foot robotic arm for what will likely be only 5-10 seconds of contact after two years of orbiting the rock. On its approach, the craft will have to dodge boulders the size of buildings. If the mission succeeds, the spacecraft and its samples will parachute home to the Utah desert in 2023.

Dig deeper: Read Julie Borg’s report about some of the exciting discoveries astronomers made last year.