Early spectral data from the Origins, Spectral Interpretation, Resource Identification, and Security-Regolith Explorer (OSIRIS-REx) mission reveal evidence for abundant hydrated minerals on the surface of near-Earth asteroid (101955) Bennu in the form of a near-infrared absorption near 2.7 µm and thermal infrared spectral features that are most similar to those of aqueously altered CM-type carbonaceous chondrites. We observe these spectral features across the surface of Bennu, and there is no evidence of substantial rotational variability at the spatial scales of tens to hundreds of metres observed to date. In the visible and near-infrared (0.4 to 2.4 µm) Bennu’s spectrum appears featureless and with a blue (negative) slope, confirming previous ground-based observations. Bennu may represent a class of objects that could have brought volatiles and organic chemistry to Earth.
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The data that support the plots within this paper and other findings of this study are available from the corresponding author upon reasonable request. Raw and calibrated spectral data will be available via the Planetary Data System (PDS) (https://sbn.psi.edu/pds/resource/orex). Data are delivered to the PDS according to the OSIRIS-REx Data Management Plan available in the OSIRIS-REx PDS archive. Higher-level products will be available in the PDS one year after departure from the asteroid. Laboratory spectral data are deposited in the spectral library hosted by Arizona State University (http://speclib.mars.asu.edu/).
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This material is based on work supported by NASA under Contract NNM10AA11C issued through the New Frontiers Program. T. Burbine, F. S. Anderson and J. Joseph provided considerable assistance with early software development for the spectral analysis working group. H. Campins, R. Binzel and E. Dotto participated in discussions of space weathering and the spectral results. C. Wolner provided helpful copyediting support. The J-Asteroid software tool and development team at ASU enabled visualization of the spectral data that was critical to the analysis. The authors also extend their gratitude to the following people without whom this work would not have been possible: the instrument teams at NASA Goddard Spaceflight Center (GSFC) and Arizona State University; the spacecraft teams at GSFC, KinetX and Lockheed Martin; the science planning and operations teams at the University of Arizona; and the Science Processing and Operations Center staff at the University of Arizona. INAF is supported by Italian Space Agency agreement no. 2017-37-H.0. The French co-authors acknowledge support from CNES. B.R. acknowledges the support of the Royal Astronomical Society in the form of a research fellowship.
The authors declare no competing interests.
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Hamilton, V.E., Simon, A.A., Christensen, P.R. et al. Evidence for widespread hydrated minerals on asteroid (101955) Bennu. Nat Astron 3, 332–340 (2019). https://doi.org/10.1038/s41550-019-0722-2
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