OSIRIS-REx seeks answers to the questions that are central to the human experience: Where did we come from? What is our destiny? Asteroids, the leftover debris from the solar system formation process, can answer these questions and teach us about the history of the sun and planets.

The OSIRIS-REx spacecraft is traveling to Bennu, a carbonaceous asteroid whose regolith may record the earliest history of our solar system. Bennu may contain the molecular precursors to the origin of life and the Earth’s oceans. Bennu is also one of the most potentially hazardous asteroids, as it has a relatively high probability of impacting the Earth late in the 22nd century. OSIRIS-REx will determine Bennu’s physical and chemical properties, which will be critical to know in the event of an impact mitigation mission. Finally, asteroids like Bennu contain natural resources such as water, organics, and precious metals. In the future, these asteroids may one day fuel the exploration of the solar system by robotic and manned spacecraft.


OSIRIS-REx’s key science objectives include:

  • Return and analyze a sample of Bennu’s surface
  • Map the asteroid
  • Document the sample site
  • Measure the orbit deviation caused by non-gravitational forces (the Yarkovsky effect)
  • Compare observations at the asteroid to ground-based observations

OSIRIS-REx is led by Dr. Dante Lauretta, the mission’s Principal Investigator, based at the University of Arizona’s Lunar and Planetary Laboratory.


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.

Learn more and watch the story of Bennu’s Journey.