What do we know and how do we know it?
Telescopic observations have helped define the orbit of Bennu. Bennu (click here to read about how asteroids are named) is a near-Earth object (click here to read about what a Near-Earth Object is). It completes an orbit of the Sun every 436.604 days (1.2 years). This orbit takes it close to the Earth every six years. Although the orbit is reasonably well known, scientists continue to refine it. It is critical to know the orbit of Bennu because recent calculations produced a 1 in 1800 chance of impact with Earth in the year 2182. In Fall 2011, scientists at the Arecibo Observatory made additional radar observations to provide researchers with data about Bennu. Part of the OSIRIS-REx mission is to refine understanding of effects on this orbit and produce information to refine the calculations of the orbit and its intersection with Earth’s. Will Earth and Bennu be in the same place at the same time and when?
Telescopic observations have revealed some basic properties of Bennu. They indicate that Bennu is very dark. Scientists have classified it as a B-type asteroid. B-type is a rare subgroup of the dark, carbonaceous C-type asteroids. These asteroids are considered “primitive” having undergone little processing from their time of formation.
What are the specific science objectives?
The science objectives of the mission define the questions we want to ask about the asteroid and the information we want to learn through sampling, mapping and measuring it.
Return and Analyze a Sample
Return and analyze a sample of pristine carbonaceous asteroid regolith in an amount sufficient to study the nature, history, and distribution of its constituent minerals and organic material.
Create Maps of the Asteroid
Map the global properties, chemistry, and mineralogy of a primitive carbonaceous asteroid to characterize its geologic and dynamic history and provide context for the returned samples.
Document the Sample Site
Document the texture, morphology, geochemistry, and spectral properties of the regolith at the sampling site in situ at scales down to millimeters.
Measure the Orbit Deviations
Measure the Yarkovsky effect, a thermal force on the object, on a potentially hazardous asteroid and constrain the asteroid properties that contribute to this effect.
Compare to Telescope-based Observations
Characterize the integrated global properties of a primitive carbonaceous asteroid to allow for direct comparison with ground-based telescopic data of the entire asteroid population.