NASA's OSIRIS-REx probe will visit a second asteroid

NASA's OSIRIS-REx spacecraft will have another mission after it drops off a sample from the asteroid Bennu. The agency has extended the probe's mission to have it study the near-Earth asteroid Apophis for 18 months. The mission will be renamed OSIRIS-APEX (OSIRIS-Apophis Explorer), and the craft will maneuver toward the space rock 30 days after its September 24th, 2023 Earth fly-by. It won't gather a sample, though. Instead, it will blast the surface with thrusters to expose the subsurface for examination.

Apophis originally drew interest over fears it would strike the Earth in 2029. Researchers put that worry to rest, but it's still a highly valuable subject. It will have the closest approach of any known asteroid its size (about 1,000ft), and scientists are eager to study the effect of Earth's gravitational pull on the object. And unlike Bennu, which is tied to carbonaceous chondrite meteorites, Apophis is associated with the regular chondrite variety.

The extension won't come cheap. A visit to Apophis will add $200 million to the cost ceiling of a mission that's already expected to cost $1.16 billion. Even so, it might be worthwhile if it helps humanity better understand asteroids and the risks they may pose to Earth.