Abstract
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.
This is a preview of subscription content, access via your institution
Access options
Access Nature and 54 other Nature Portfolio journals
Get Nature+, our best-value online-access subscription
$29.99 / 30 days
cancel any time
Subscribe to this journal
Receive 12 digital issues and online access to articles
$119.00 per year
only $9.92 per issue
Buy this article
- Purchase on SpringerLink
- Instant access to full article PDF
Prices may be subject to local taxes which are calculated during checkout
Similar content being viewed by others
Data availability
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/).
References
Clark, B. E. et al. Asteroid (101955) 1999 RQ36: spectroscopy from 0.4 to 2.4 µm and meteorite analogs. Icarus 216, 462–475 (2011).
Reuter, D. C. et al. The OSIRIS-REx Visible and InfraRed Spectrometer (OVIRS): spectral maps of the asteroid Bennu. Space Sci. Rev. 214, 54 (2018).
Christensen, P. R. et al. The OSIRIS-REx Thermal Emission Spectrometer (OTES) instrument. Space Sci. Rev. 214, 87 (2018).
Lauretta, D. S. et al. OSIRIS-REx: sample return from asteroid (101955) Bennu. Space Sci. Rev. 212, 925–984 (2017).
DellaGiustina, D. N. et al. Properties of rubble-pile asteroid (101955) Bennu from OSIRIS-REx imaging and thermal analysis. Nat. Astron. https://doi.org/10.1038/s41550-019-0731-1 (2019).
Rizk, B. et al. OCAMS: the OSIRIS-REx camera suite. Space Sci. Rev. 214, 26 (2018).
Van Schmus, W. R. & Wood, J. A. A chemical-petrologic classification for the chondritic meteorites. Geochim. Cosmochim. Acta 31, 747–765 (1967).
Binzel, R. P. et al. Spectral slope variations for OSIRIS-REx target asteroid (101955) Bennu: possible evidence for a fine-grained regolith equatorial ridge. Icarus 256, 22–29 (2015).
Cloutis, E. A., Hiroi, T., Gaffey, M. J. & Alexander, C. M. O. D. Spectral reflectance properties of carbonaceous chondrites: 1. CI chondrites. Icarus 212, 180–209 (2011).
Cloutis, E. A., Hudon, P., Hiroi, T., Gaffey, M. J. & Mann, P. Spectral reflectance properties of carbonaceous chondrites: 2. CM chondrites. Icarus 216, 309–346 (2011).
Thompson, M. S., Loeffler, M. J., Morris, R. V., Keller, L. P. & Christofferson, R. Spectral and chemical effects of simulated space weathering of the Murchison CM2 carbonaceous chondrite. Icarus 319, 499–511 (2019).
Lauretta, D. S. et al. The unexpected surface of asteroid (101955) Bennu. Nature https://doi.org/10.1038/s41586-019-1033-6 (2019).
Izawa, M. R. M. et al. Spectral reflectance properties of magnetites: implications for remote sensing. Icarus 319, 525–539 (2019).
Brunetto, R. et al. Ion irradiation of Allende meteorite probed by visible, IR, and Raman spectroscopies. Icarus 237, 278–292 (2014).
Lantz, C., Binzel, R. P. & DeMeo, F. E. Space weathering trends on carbonaceous asteroids: a possible explanation for Bennu’s blue slope? Icarus 302, 10–17 (2018).
Miyamoto, M. & Zolensky, M. E. Infrared diffuse reflectance spectra of carbonaceous chondrites: amount of hydrous materials. Meteoritics 29, 849–853 (1994).
Moroz, L. V., Schmidt, M., Schade, U., Hiroi, T. & Ivanova, M. A. Synchrotron-based infrared microspectroscopy as a useful tool to study hydration states of meteorite constituents. Meteorit. Planet. Sci. 41, 1219–1230 (2006).
Beck, P. et al. Hydrous mineralogy of CM and CI chondrites from infrared spectroscopy and their relationship with low albedo asteroids. Geochim. Cosmochim. Acta 74, 4881–4892 (2010).
Takir, D. et al. Nature and degree of aqueous alteration in CM and CI carbonaceous chondrites. Meteorit. Planet. Sci. 48, 1618–1637 (2013).
Zolensky, M. E. & McSween, H. Y. Jr in Meteorites and the Early Solar System (eds Kerridge, J. F. & Matthews, M. S.) 114–143 (Univ, Arizona Press, Tucson, 1988).
Brearley, A. J. & Jones, R. H. in Reviews in Mineralogy Volume 36: Planetary Materials (ed. Papike, J. J.) Ch. 3 (Mineralogical Society of America, Chantilly, 1998).
Abreu, N. M. Fine-scale Mineralogical Study of the Matrices of CR Carbonaceous Chondrites: Insights on Early Solar System Processes. PhD thesis, Univ. New Mexico (2007).
Bishop, J. L., Lane, M. D., Dyar, M. D. & Brown, A. J. Reflectance and emission spectroscopy study of four groups of phyllosilicates: smectites, kaolinite-serpentines, chlorites and micas. Clay Minerals 43, 35–54 (2008).
Lantz, C. et al. Ion irradiation of the Murchison meteorite: visible to mid-infrared spectroscopic results. Astron. Astrophys. 577, A41 (2015).
Rivkin, A. S. et al. in Asteroids IV (eds Michel, P., DeMeo, F. E. & Bottke, W. F.) 65–87 (Univ. Arizona, Tucson, 2015).
Takir, D. & Emery, J. P. Outer main belt asteroids: identification and distribution of four 3-µm spectral groups. Icarus 219, 641–654 (2012).
Rivkin, A. S., Howell, E. S., Emery, J. P., Volquardsen, E. L. & DeMeo, F. E. Toward a taxonomy of asteroid spectra in the 3-µm region. Eur. Planet Sci. Congr. 7, 359 (2012).
Rivkin, A. S. & Emery, J. P. Detection of ice and organics on an asteroidal surface. Nature 464, 1322–1323 (2010).
Campins, H. et al. Water ice and organics on the surface of the asteroid 24 Themis. Nature 464, 1320–1321 (2010).
Sugita, S. et al. The geomorphology, color, and thermal properties of Ryugu: Implications for parent-body processes. Science https://doi.org/10.1126/science.aaw0422 (in the press).
Kitazato, K. et al. The surface composition of asteroid 162173 Ryugu from Hayabusa2 near-infrared spectroscopy. Science https://doi.org/10.1126/science.aav7432 (in the press).
Emery, J. P. et al. Thermal infrared observations and thermophysical characterization of OSIRIS-REx target asteroid (101955) Bennu. Icarus 234, 17–35 (2014).
Lim, L. F. et al. The global thermal infrared spectrum of Bennu: comparison with Spitzer IRS asteroid spectra. In Am. Geophys. Union Fall Meet. 2018 abstr. P33C-3844 (American Geophysical Union, 2018).
Howard, K. T., Alexander, C. M. O. D., Schrader, D. L. & Dyl, K. A. Classification of hydrous meteorites (CR, CM and C2 ungrouped) by phyllosilicate fraction: PSD-XRD modal mineralogy and planetesimal environments. Geochim. Cosmochim. Acta 149, 206–222 (2015).
King, A. J., Schofield, P. F. & Russell, S. S. Type 1 aqueous alteration in CM carbonaceous chondrites: implications for the evolution of water-rich asteroids. Meteorit. Planet. Sci. 52, 1197–1215 (2017).
McSween, H. Y. Jr Are carbonaceous chondrites primitive or processed? A review. Rev. Geophys. Space Phys. 17, 1059–1078 (1979).
Morlok, A. et al. Brecciation and chemical heterogeneity of CI chondrites. Geochim. Cosmochim. Acta 70, 5371–5394 (2006).
Rubin, A. E., Trigo-Rodríguez, J. M., Huber, H. & Wasson, J. T. Progressive aqueous alteration of CM carbonaceous chondrites. Geochim. Cosmochim. Acta 71, 2361–2382 (2007).
Hamilton, V. E. et al. Spectral classification of ungrouped carbonaceous chondrites. II: Parameters and comparison to independent measures. In 49th Lunar Planet. Sci. Conf. abstr. 1753 (LPI, 2018).
Hamilton, V. E. Thermal infrared emission spectroscopy of the pyroxene mineral series. J. Geophys. Res. 105, 9701–9716 (2000).
Hamilton, V. E. Thermal infrared (vibrational) spectroscopy of Mg-Fe olivines: a review and applications to determining the composition of planetary surfaces. Chem. Erde 70, 7–33 (2010).
Walsh, K. J. et al. Craters, boulders and regolith of (101955) Bennu indicative of an old and dynamic surface. Nat. Geosci. https://doi.org/10.1038/s41561-019-0326-6 (2019).
Scheeres, D. J. et al. The dynamic geophysical environment of (101955) Bennu based on OSIRIS-REx measurements. Nat. Astron. https://doi.org/10.1038/s41550-019-0721-3 (2019).
Reuter, D. C. et al. Ralph, a visible/infrared imager for the New Horizons Pluto/Kuiper Belt mission. Space Sci. Rev. 140, 129–154 (2008).
Simon, A. A. et al. In-flight calibration and performance of the OSIRIS-REx Visible and IR Spectrometer (OVIRS). Remote Sens. 10, 1486 (2018).
Hergenrother, C. W. et al. Operational environment and rotational acceleration of asteroid (101955) Bennu from OSIRIS-REx observations. Nat. Commun. https://doi.org/10.1038/s41467-019-09213-x (2019).
Barnouin, O. S. et al. Shape of (101955) Bennu indicative of a rubble pile with internal stiffness. Nat. Geosci. https://doi.org/10.1038/s41561-019-0330-x (2019).
Christensen, P. R. et al. Mars Global Surveyor Thermal Emission Spectrometer experiment: investigation description and surface science results. J. Geophys. Res. 106, 23823–23871 (2001).
Christensen, P. R. et al. Miniature thermal emission spectrometer for the Mars exploration rovers. J. Geophys. Res. 108, 8064 (2003).
Rogers, A. D. & Aharonson, O. Mineralogical composition of sands in Meridiani Planum determined from Mars Exploration Rover data and comparison to orbital measurements. J. Geophys. Res. 113, E06S14 (2008).
Quirico, E. et al. Origin of insouble organic matter in type 1 and 2 chondrites: new clues, new questions. Geochim. Cosmochim. Acta 136, 80–99 (2014).
Quirico, E. et al. Prevalence and nature of heating processes in CM and C2-ungrouped chondrites as revealed by insoluble organic matter. Geochim. Cosmochim. Acta 241, 17–37 (2018).
Hamilton, V. E. Spectral classification of ungrouped carbonaceous chondrites. I: Data collection and processing. In 49th Lunar Planet. Sci. Conf. abstr. 1759 (LPI, 2018).
Logan, L. M. & Hunt, G. R. Emission spectra of particulate silicates under simulated lunar conditions. J. Geophys. Res. 75, 6539–6548 (1970).
Henderson, B. G. & Jakosky, B. M. Near-surface thermal gradients and mid-IR emission spectra: a new model including scattering and application to real data. J. Geophys. Res. 102, 6567–6580 (1997).
Donaldson Hanna, K. L. et al. Spectral characterization of analog samples in anticipation of OSIRIS-REx’s arrival at Bennu: a blind test study. Icarus 319, 701–723 (2019).
Acknowledgements
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.
Author information
Authors and Affiliations
Consortia
Contributions
V.E.H. is the spectral analysis working group lead, the OTES deputy instrument scientist, and wrote this manuscript. A.A.S. is the spectral analysis working group deputy, the OVIRS deputy instrument scientist, and led the calibration of the OVIRS data and production of the disk-integrated average spectrum. P.R.C. is the OTES instrument scientist and led the calibration of OTES data. D.C.R. is the OVIRS instrument scientist. B.E.C. is the OSIRIS-REx Mission Asteroid Scientist. M.A.B., H.H.K., R.D.H. and A.P. contributed to the analysis of the OVIRS 2.7 µm band. N.E.B. hosts the laboratory that made the simulated asteroid environment spectral measurements. W.V.B. is the mission instrument scientist and contributed to ensuring the mission plan enables the instruments to meet their observation requirements. J.R.B., E.A.C., S.F., C.L., J.-Y.L., F.M., S.A.S., C.A.T. and X.-D.Z. contributed to the development of science pipeline software. H.C.C. Jr is the mission sample scientist and helped guide the selection and acquisition of the meteorite samples used in this work. K.L.D.H. measured the samples shown in Fig. 4b. J.P.E. and B.R. contributed to the subtraction of thermal emission from OVIRS spectra. H.L.E. is the deputy principal investigator for the OSIRIS-REx mission. C.W.H. contributed to the data processing and analysis of OTES spectra. E.S.H. contributed to the development of science pipeline software and provided manual processing of some of the data shown in this manuscript. L.P.K. and T.J.M. helped guide the selection and acquisition of the meteorite samples used in this work. L.F.L. contributed to extensive discussions about the laboratory measurements. M.C.N. is the science team chief and contributed the resampled solar spectrum used in the calibration of OVIRS data. D.L.S. contributed to the preparation and characterization of meteorite samples used in this work. D.S.L. is the OSIRIS-REx principal investigator and the entire OSIRIS-REx Team made the Bennu encounter possible.
Corresponding author
Ethics declarations
Competing interests
The authors declare no competing interests.
Additional information
Publisher’s note: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Rights and permissions
About this article
Cite this article
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
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1038/s41550-019-0722-2
This article is cited by
-
Origin of asteroid (101955) Bennu and its connection to the New Polana family
Scientific Reports (2024)
-
Shapes, Rotations, Photometric and Internal Properties of Jupiter Trojans
Space Science Reviews (2024)
-
Space weathering record and pristine state of Ryugu samples from MicrOmega spectral analysis
Nature Astronomy (2023)
-
Space weathering acts strongly on the uppermost surface of Ryugu
Communications Earth & Environment (2023)
-
Space weathering signatures in sulfide and silicate minerals from asteroid Itokawa
Earth, Planets and Space (2022)