The OSIRIS‐REx target asteroid (101955) Bennu: Constraints on its physical,geological, and dynamical nature from astronomical observations |
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| Authors: | D S Lauretta A E Bartels M A Barucci E B Bierhaus R P Binzel W F Bottke H Campins S R Chesley B C Clark B E Clark E A Cloutis H C Connolly M K Crombie M Delbó J P Dworkin J P Emery D P Glavin V E Hamilton C W Hergenrother C L Johnson L P Keller P Michel M C Nolan S A Sandford D J Scheeres A A Simon B M Sutter D Vokrouhlický K J Walsh |
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| Institution: | 1. Lunar and Planetary Laboratory, University of Arizona, Tucson, Arizona, USA;2. NASA Goddard Space Flight Center, Greenbelt, Maryland, USA;3. Observatoire de Paris, Paris, France;4. Lockheed Martin Space Systems, Littleton, Colorado, USA;5. Massachussets Institute of Technology, Cambridge, Massachusetts, USA;6. Southwest Research Institute, Boulder, Colorado, USA;7. University of Central Florida, Orlando, Florida, USA;8. Jet Propulsion Laboratory, Pasadena, California, USA;9. Space Science Institute, Boulder, Colorado, USA;10. Ithaca College, Ithaca, New York, USA;11. University of Winnipeg, Winnipeg, Canada;12. Kingsborough Community College of CUNY, Brooklyn, New York, USA;13. The Graduate Center of CUNY, New York, New York, USA;14. AMNH, Central Park West, New York, New York, USA;15. Indigo Information Services, Tucson, Arizona, USA;16. Lagrange Laboratory, University of Nice‐Sophia Antipolis, CNRS, C?te d'Azur Observatory, Nice, France;17. University of Tennessee, Knoxville, Tennessee, USA;18. Planetary Science Institute, Tucson, Arizona, USA;19. University of British Columbia, Vancouver, Canada;20. NASA Johnson Space Center, Houston, Texas, USA;21. Arecibo Observatory, Arecibo, Puerto Rico;22. NASA Ames Research Center, Mountain View, California, USA;23. University of Colorado, Boulder, Colorado, USA;24. Institute of Astronomy, Charles University, Czech Republic |
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| Abstract: | We review the results of an extensive campaign to determine the physical, geological, and dynamical properties of asteroid (101955) Bennu. This investigation provides information on the orbit, shape, mass, rotation state, radar response, photometric, spectroscopic, thermal, regolith, and environmental properties of Bennu. We combine these data with cosmochemical and dynamical models to develop a hypothetical timeline for Bennu's formation and evolution. We infer that Bennu is an ancient object that has witnessed over 4.5 Gyr of solar system history. Its chemistry and mineralogy were established within the first 10 Myr of the solar system. It likely originated as a discrete asteroid in the inner Main Belt approximately 0.7–2 Gyr ago as a fragment from the catastrophic disruption of a large (approximately 100‐km), carbonaceous asteroid. It was delivered to near‐Earth space via a combination of Yarkovsky‐induced drift and interaction with giant‐planet resonances. During its journey, YORP processes and planetary close encounters modified Bennu's spin state, potentially reshaping and resurfacing the asteroid. We also review work on Bennu's future dynamical evolution and constrain its ultimate fate. It is one of the most Potentially Hazardous Asteroids with an approximately 1‐in‐2700 chance of impacting the Earth in the late 22nd century. It will most likely end its dynamical life by falling into the Sun. The highest probability for a planetary impact is with Venus, followed by the Earth. There is a chance that Bennu will be ejected from the inner solar system after a close encounter with Jupiter. OSIRIS‐REx will return samples from the surface of this intriguing asteroid in September 2023. |
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