Scientists chose Bennu as the target of the OSIRIS-REx mission because of its composition, size, and proximity to Earth. Bennu is a rare B-type asteroid (primitive and carbon-rich), which is expected to have organic compounds and water-bearing minerals like clays.
Equatorial Diameter: ~500 m
Polar Diameter: ~510 m
Average Speed: 63,000 mph
Rotation Period: 4.3 hrs
Orbital Period: 1.2 yrs
Orbital Inclination: 6 degrees
Earth Approach: Bennu comes close to Earth every 6 yrs
Primitive asteroids have not significantly changed since they formed nearly 4.5 billion years ago. Because of this, we hope to find organic molecules on Bennu like those that may have led to the origin of life on Earth.