Bennu likely broke off from a much larger carbon-rich asteroid about 700 million to 2 billion years ago. It likely formed in the Main Asteroid Belt between Mars and Jupiter, and has drifted much closer to Earth since then. Because its materials are so old, Bennu may contain organic molecules similar to those that could have been involved with the start of life on Earth.
Bennu's density is only about 30 percent more than water. This suggests the asteroid is probably a loose collection of rocks, like a pile of rubble.
Bennu has a close approach to Earth every six years.
The asteroid was discovered by the Lincoln Near-Earth Asteroid Research (LINEAR) survey on September 11, 1999.
Bennu has drifted into near-Earth space because of gravitational interactions with giant planets and the gentle push of heating from the Sun.
Bennu is close to Earth, it's really old and well-preserved. It might even help us in our search for clues to the origins of life—and learn how to preserve life by keeping near-Earth asteroids at bay.