The shapes of asteroids reflect interplay between their interior properties and the processes responsible for their formation and evolution as they journey through the Solar System. Prior to the OSIRIS-REx (Origins, Spectral Interpretation, Resource Identification, and Security–Regolith Explorer) mission, Earth-based radar imaging gave an overview of (101955) Bennu’s shape. Here we construct a high-resolution shape model from OSIRIS-REx images. We find that Bennu’s top-like shape, considerable macroporosity and prominent surface boulders suggest that it is a rubble pile. High-standing, north–south ridges that extend from pole to pole, many long grooves and surface mass wasting indicate some low levels of internal friction and/or cohesion. Our shape model indicates that, similar to other top-shaped asteroids, Bennu formed by reaccumulation and underwent past periods of fast spin, which led to its current shape. Today, Bennu might follow a different evolutionary pathway, with an interior stiffness that permits surface cracking and mass wasting.
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Most of the image and digital terrain analyses shown were undertaken with the JHUAPL Small Body Mapping Tool (SBMT). It is available for the analysis of a broad suite of asteroid and comet data at sbmt.jhuapl.edu. On release of the OSIRIS-REx data by the PDS, a version of SBMT with those data will be made publicly available. The spherical harmonic assessment was performed using the Spherical Harmonic Transform Library hosted at Mathworks (https://www.mathworks.com/matlabcentral/fileexchange/43856-real-complex-spherical-harmonic-transform-gaunt-coefficients-and-rotations). The SPC code used to develop the GDTM of Bennu can be made available with special permission. Please contact the corresponding author for additional information on how.
Raw through to calibrated data sets 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 (for example, the GDTM) discussed here will be available in the PDS one year after departure from the asteroid.
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Nolan, M. et al. Shape model and surface properties of the OSIRIS-REx target asteroid (101955) Bennu from radar and lightcurve observations. Icarus 226, 629–640 (2013).
Hergenrother, C. W. et al. Lightcurve, color and phase function photometry of the OSIRIS-REx target asteroid (101955) Bennu. Icarus 226, 663–670 (2013).
Rizk, B. et al. OCAMS: the OSIRIS-REx Camera Suite. Space Sci. Rev. 214, 26 (2018).
Gaskell, R. W. et al. Characterizing and navigating small bodies with imaging data. Meteorit. Planet. Sci. 43, 1049–1061 (2008).
Daly, M. G. et al. The OSIRIS-REx Laser Altimeter (OLA) investigation and instrument. Space Sci. Rev. 198, 1–26 (2017).
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).
Lauretta, D. S. et al. The unexpected surface of asteroid (101955) Bennu. Nature https://doi.org/10.1038/s41586-019-1033-6 (2019).
Abe, S. et al. Mass and local topography measurements of Itokawa by Hayabusa. Science 312, 1344–1347 (2006).
Watanabe, S. et al. Hayabusa2 arrives at the carbonaceous asteroid 162173 Ryugu — a spinning-top-shaped rubble pile. Science https://doi.org/10.1126/science.aav8032 (in the press).
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).
Hamilton, V. E. et al. Evidence for widespread hydrated minerals on asteroid (101955) Bennu. Nat. Astron. https://doi.org/10.1038/s41550-019-0722-2 (2019).
Macke, R. J., Consolmagno, G. J. & Britt, D. T. Density, porosity, and magnetic susceptibility of carbonaceous chondrites. Meteorit. Planet. Sci. 46, 1842–1862 (2011).
Scheeres, D. J., Britt, D., Carry, D. & Holsapple, K. A. in Asteroids IV (eds Michel, P., DeMeo, F. E. & Bottke, W. F.) 745–766 (University of Arizona Press, Tucson, 2015).
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).
Cheng, A. F. et al. Small-scale topography of 433 Eros from laser altimetry and imaging. Icarus 155, 51–74 (2002).
Barnouin-Jha, O. S. et al. Small-scale topography of 25143 Itokawa from the Hayabusa laser altimeter. Icarus 198, 108–124 (2008).
Scheeres, D. J. et al. The geophysical environment of Bennu. Icarus 276, 116–140 (2016).
Mazrouei, S., Daly, M. G., Barnouin, O. S., Ernst, C. M. & DeSouza, I. Block distributions on Itokawa. Icarus 229, 181–189 (2014).
Marchi, S., Chapman, C. R., Barnouin, O. S., Richardson, J. E., Vincent, J.-B. in Asteroids IV (eds Michel, P., DeMeo, F. E. & Bottke, W. F.) 725–744 (University of Arizona Press, Tucson, 2015).
Thomas, P. C. et al. Mathilde: size, shape, and geology. Icarus 140, 17–27 (1999).
Hirata, N. et al. A survey of possible impact structures on 25143 Itokawa. Icarus 200, 486–502 (2009).
Bart, G. D. & Melosh, H. J. Using lunar boulders to distinguish primary from distant secondary impact craters. Geophys. Res. Lett. 34, L07203 (2007).
Michel, P. & Richardson, D. C. Collision and gravitational reaccumulation: possible formation mechanism of the asteroid Itokawa. Astron. Astrophys. 554, 1–4 (2013).
Holsapple, K. A. Equilibrium figures of spinning bodies with self-gravity. Icarus 172, 272–303 (2004).
Iverson, R. M. The physics of debris flows. Rev. Geophys. 35, 245–296 (1997).
Prockter, L. et al. Surface expressions of structural features on Eros. Icarus 155, 75–93 (2002).
Walsh, K. J., Richardson, D. C. & Michel, P. Rotational breakup as the origin of small binary asteroids. Nature 454, 188–191 (2008).
Hirabayashi, M., Sanchez, P. & Scheeres, D. J. Internal structure of asteroids having surface shedding due to rotational instability. Astrophys. J. 808, 63 (2015).
Zhang, Y. et al. Creep stability of the proposed AIDA mission target 65803 Didymos: I. Discrete cohesionless granular physics model. Icarus 294, 98–123 (2017).
Barnouin, O. S., Michel, P. & Richardson, D. C. A preliminary assessment of asteroid shapes produced by impact disruption and re-creation: application to the AIDA target. Geophys. Res. Abstracts 18, 17584 (2016).
Michel, P. et al. Disruption and reaccumulation as the possible origins of Ryugu and Bennu top shapes. In Lunar Planetary Sci. Conf. 50 abstr. 1659 (2019).
Rubincam, D. P. Radiative spin-up and spin-down of small asteroids. Icarus 148, 2–11 (2000).
Hirabayashi, M. & Scheeres, D. J. Stress and failure analysis of rapidly rotating asteroid (29075) 1950 DA. Astrophys J. Lett. 798, L8 (2014).
Sanchez, P. & Scheeres, D. J. Disruption patterns of rotating self-gravitating aggregates: a survey on angle of friction and tensile strength. Icarus 271, 453–471 (2016).
Zhang, Y. et al. Rotational failure of rubble-pile bodies: influences of shear and cohesive strengths. Astrophys. J. 857, 15 (2018).
Miyamoto, H. et al. Regolith migration and sorting on asteroid Itokawa. Science 316, 1011 (2007).
Delbo, M. et al. Thermal fatigue as the origin of regolith on small asteroids. Nature 508, 233–236 (2014).
Barnouin, O. S. et al. Altimetry efforts at Bennu. In Lunar Planetary Sci. Conf. 49 abstr. 1041 (2018).
Gaskell, R. W. Gaskell Eros Shape Model V1.0. NEAR-A-MSI-5-EROSSHAPE-V1.0. NASA Planetary Data System (NASA, 2008).
Gaskell, R. W. et al. Itokawa Shape Model V1.0. HAY-A-AMICA-5-ITOKAWASHAPE-V1.0. NASA Planetary Data System (NASA, 2008).
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).
Richardson, J. E. & Bowling, T. J. Investigating the combined effects of shape, density, and rotation on small body surface slopes and erosion rates. Icarus 234, 53–65 (2014).
This material is based on work supported by NASA under contract NNM10AA11C issued through the New Frontiers Program. The Canadian team members were supported by the Canadian Space Agency. P.M. acknowledges funding support from the French space agency CNES and from Academies of Excellence: Complex systems and Space, environment, risk, and resilience, part of the IDEX JEDI of the Université Côte d’Azur.
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Nature Reviews Materials (2019)
Nature Geoscience (2019)
Nature Astronomy (2019)
The operational environment and rotational acceleration of asteroid (101955) Bennu from OSIRIS-REx observations
Nature Communications (2019)
Nature Astronomy (2019)