Skip to main content

Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

Rotational breakup as the origin of small binary asteroids

Abstract

Asteroids with satellites are observed throughout the Solar System, from subkilometre near-Earth asteroid pairs to systems of large and distant bodies in the Kuiper belt. The smallest and closest systems are found among the near-Earth and small inner main-belt asteroids, which typically have rapidly rotating primaries and close secondaries on circular orbits. About 15 per cent of near-Earth and main-belt asteroids with diameters under 10 km have satellites1,2. The mechanism that forms such similar binaries in these two dynamically different populations was hitherto unclear. Here we show that these binaries are created by the slow spinup of a ‘rubble pile’ asteroid by means of the thermal YORP (Yarkovsky–O’Keefe–Radzievskii–Paddack) effect. We find that mass shed from the equator of a critically spinning body accretes into a satellite if the material is collisionally dissipative and the primary maintains a low equatorial elongation. The satellite forms mostly from material originating near the primary’s surface and enters into a close, low-eccentricity orbit. The properties of binaries produced by our model match those currently observed in the small near-Earth and main-belt asteroid populations, including 1999 KW4 (refs 3, 4).

This is a preview of subscription content

Access options

Buy article

Get time limited or full article access on ReadCube.

$32.00

All prices are NET prices.

Figure 1: Asteroid shape change during mass loss.
Figure 2: Primary and secondary properties during satellite formation.
Figure 3: Binary formation for an asteroid with a rigid core.

References

  1. Pravec, P. et al. Photometric survey of binary near-Earth asteroids. Icarus 181, 63–93 (2006)

    ADS  Article  Google Scholar 

  2. Pravec, P. & Harris, A. W. Binary asteroid population. Icarus 190, 250–259 (2007)

    ADS  Article  Google Scholar 

  3. Ostro, S. J. et al. Radar imaging of binary near-Earth asteroid (66391) 1999 KW4. Science 314, 1276–1280 (2006)

    CAS  ADS  Article  Google Scholar 

  4. Scheeres, D. J. et al. Dynamical configuration of binary near-Earth asteroid (66391) 1999 KW4. Science 314, 1280–1283 (2006)

    CAS  ADS  Article  Google Scholar 

  5. Richardson, D. C. & Walsh, K. J. Binary minor planets. Annu. Rev. Earth Planet. Sci. 34, 47–81 (2006)

    CAS  ADS  Article  Google Scholar 

  6. Walsh, K. J. & Richardson, D. C. Binary near-Earth asteroid formation: Rubble pile model of tidal disruptions. Icarus 180, 201–216 (2006)

    ADS  Article  Google Scholar 

  7. Walsh, K. J. & Richardson, D. C. A steady-state model of NEA binaries formed by tidal disruption of gravitational aggregates. Icarus 193, 553–566 (2008)

    ADS  Article  Google Scholar 

  8. Michel, P. et al. Collisions and gravitational reaccumulation: forming asteroid families and satellites. Science 294, 1696–1700 (2001)

    CAS  ADS  Article  Google Scholar 

  9. Durda, D. D. et al. The formation of asteroid satellites in catastrophic impacts: Results from numerical simulations. Icarus 167, 382–396 (2004)

    ADS  Article  Google Scholar 

  10. Rubincam, D. P. Radiative spin-up and spin-down of small asteroids. Icarus 148, 2–11 (2000)

    ADS  Article  Google Scholar 

  11. Paddack, S. J. & Rhee, J. W. Rotational bursting of interplanetary dust particles. Geophys. Res. Lett. 2, 365–367 (1975)

    ADS  Article  Google Scholar 

  12. Lowry, S. C. et al. Direct detection of the asteroidal YORP effect. Science 316, 272–274 (2007)

    CAS  ADS  Article  Google Scholar 

  13. Taylor, P. A. et al. Spin rate of asteroid (54509) 2000 PH5 increasing due to the YORP effect. Science 316, 274–277 (2007)

    CAS  ADS  Article  Google Scholar 

  14. Kaasalainen, M., Dˇurech, J., Warner, B. D., Kugly, Y. N. & Gaftonyuk, N. N. Acceleration of the rotation of asteroid 1862 Apollo by radiation torques. Nature 446, 420–422 (2007)

    CAS  ADS  Article  Google Scholar 

  15. C´uk, M. Formation and destruction of small binary asteroids. Astrophys. J. 659, 57–60 (2007)

    Article  Google Scholar 

  16. Pravec, P. & Harris, A. W. Fast and slow rotation of asteroids. Icarus 148, 12–20 (2000)

    ADS  Article  Google Scholar 

  17. Richardson, D. C., Leinhardt, Z. M., Melosh, H. J., Bottke, W. F. & Asphaug, E. in Asteroids III (eds Bottke, W. F. Jr, Cellino, A., Paolicchi, P. & Binzel, R. P.) 501–515 (Univ. of Arizona Press, Tucson, AZ, 2002)

    Google Scholar 

  18. Richardson, D. C., Elankumaran, R. E. & Sanderson, R. E. Numerical experiments with rubble piles: equilibrium shapes and spins. Icarus 173, 349–361 (2005)

    ADS  Article  Google Scholar 

  19. Fujiwara, A. et al. The rubble-pile asteroid Itokawa as observed by Hayabusa. Science 312, 1330–1334 (2006)

    CAS  ADS  Article  Google Scholar 

  20. Supulver, K. D., Bridges, F. G. & Lin, D. N. C. The coefficient of restitution of ice particles in glancing collisions: Experimental results for unfrosted surfaces. Icarus 113, 188–199 (1995)

    ADS  Article  Google Scholar 

  21. Fujii, Y. & Nakamura, A. M. Compaction and fragmentation of porous targets at low velocity collisions. Lunar Planet. Sci. Conf. XXXVIII abstract 1525 (2007)

Download references

Acknowledgements

We thank W. F. Bottke and A. Harris for their constructive reviews. K.J.W. and D.C.R. acknowledge support from the National Science Foundation under grants AST0307549 and AST0708110. K.J.W. and P.M. also had the support of the European Space Agency’s Advanced Concepts Team on the basis of the Ariadna study 07/4111 ‘Asteroid Centrifugal Fragmentation’, and of the French Programme National de Planétologie. K.W. is also supported by the Henri Poincaré fellowship at the Observatoire de la Côte d’Azur, Nice, France. We acknowledge the use of the Mésocentre de Calcul-SIGAMM hosted at the Observatoire de la Côte d’Azur, Nice, France. Some simulations were performed at the University of Maryland with the Department of Astronomy borg cluster and the Office of Information Technology High Performance Computing Cluster. Raytracing for Figs 1 and 3 was performed with the Persistence of Vision Raytracer.

Author information

Authors and Affiliations

Authors

Corresponding author

Correspondence to Kevin J. Walsh.

PowerPoint slides

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Walsh, K., Richardson, D. & Michel, P. Rotational breakup as the origin of small binary asteroids. Nature 454, 188–191 (2008). https://doi.org/10.1038/nature07078

Download citation

  • Received:

  • Accepted:

  • Issue Date:

  • DOI: https://doi.org/10.1038/nature07078

Further reading

Comments

By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.

Search

Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing