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.

A basin-free spherical shape as an outcome of a giant impact on asteroid Hygiea

Abstract

(10) Hygiea is the fourth largest main belt asteroid and the only known asteroid whose surface composition appears similar to that of the dwarf planet (1) Ceres1,2, suggesting a similar origin for these two objects. Hygiea suffered a giant impact more than 2 Gyr ago3 that is at the origin of one of the largest asteroid families. However, Hygeia has never been observed with sufficiently high resolution to resolve the details of its surface or to constrain its size and shape. Here, we report high-angular-resolution imaging observations of Hygiea with the VLT/SPHERE instrument (~20 mas at 600 nm) that reveal a basin-free nearly spherical shape with a volume-equivalent radius of 217 ± 7 km, implying a density of 1,944 ± 250 kg m3 to 1σ. In addition, we have determined a new rotation period for Hygiea of ~13.8 h, which is half the currently accepted value. Numerical simulations of the family-forming event show that Hygiea’s spherical shape and family can be explained by a collision with a large projectile (diameter ~75–150 km). By comparing Hygiea’s sphericity with that of other Solar System objects, it appears that Hygiea is nearly as spherical as Ceres, opening up the possibility for this object to be reclassified as a dwarf planet.

This is a preview of subscription content, access via your institution

Access options

Rent or buy this article

Prices vary by article type

from$1.95

to$39.95

Prices may be subject to local taxes which are calculated during checkout

Fig. 1: VLT/SPHERE deconvolved images of the four largest main belt objects.
Fig. 2: Comparison between the deconvolved images of Hygiea and the corresponding shape model projections.
Fig. 3: SPH simulations reveal a nearly spherical shape for Hygiea following post-impact reaccumulation.
Fig. 4: Asphericity of Solar System objects as a function of their mean radius.

Similar content being viewed by others

Data availability

As soon as papers for our large programme are accepted for publication, we will make the corresponding reduced and deconvolved adaptive optics images and 3D shape models publicly available at http://observations.lam.fr/astero/.

Code availability

The code used to generate the 3D shape is freely available at https://github.com/matvii/ADAM. The code used to perform the SPH simulations is freely available at https://gitlab.com/sevecekp/sph.

References

  1. Takir, D. & Emery, J. P. Outer main belt asteroids: identification and distribution of four 3-μm spectral groups. Icarus 219, 641–654 (2012).

    Article  ADS  Google Scholar 

  2. Vernazza, P. et al. Different origins or different evolutions? Decoding the spectral diversity among C-type asteroids. Astron. J. 153, 72 (2017).

    Article  ADS  Google Scholar 

  3. Carruba, V., Domingos, R. C., Huaman, M. E., dos Santos, C. R. & Souami, D. Dynamical evolution and chronology of the Hygiea asteroid family. Mon. Not. R. Astron. Soc. 437, 2279–2290 (2014).

    Article  ADS  Google Scholar 

  4. Vernazza, P. et al. The impact crater at the origin of the Julia family detected with VLT/SPHERE? Astron. Astrophys. 618, A154 (2018).

    Article  Google Scholar 

  5. Thalmann, C. et al. SPHERE ZIMPOL: overview and performance simulation. Proc. SPIE 7014, 70143F (2008).

  6. Fusco, T. et al. Deconvolution of astronomical images obtained from ground-based telescopes with adaptive optics. Proc. SPIE 4839, 1065–1075 (2003).

  7. Fetick, R. et al. Closing the gap between Earth-based and interplanetary mission observations: Vesta seen by VLT/SPHERE. Astron. Astrophys. 623, A6 (2019).

    Article  Google Scholar 

  8. Viikinkoski, M., Kaasalainen, M. & Durech, J. ADAM: a general method for using various data types in asteroid reconstruction. Astron. Astrophys. 576, A8 (2015).

  9. Michalowski, T. et al. The spin vector of asteroid 10 Hygiea. Astron. Astrophys. Suppl. Ser. 91, 53–59 (1991).

    ADS  Google Scholar 

  10. Chandrasekhar, R. Ellipsoidal Figures of Equilibrium (Dover Publications, 1987).

  11. Park, R. S. et al. High-resolution shape model of Ceres from stereophotoclinometry using Dawn imaging data. Icarus 319, 812–827 (2019).

    Article  ADS  Google Scholar 

  12. Nesvorný, D., Brož, M. & Carruba, V. in Asteroids IV (eds Michel, P. et al.) 297–321 (Univ. Arizona Press, 2015).

  13. Thomas, P. C. et al. Impact excavation on asteroid 4 Vesta: Hubble Space Telescope results. Science 277, 1492–1495 (1997).

    Article  ADS  Google Scholar 

  14. Benz, W. & Asphaug, E. Impact simulations with fracture. I. Method and tests. Icarus 107, 98–116 (1994).

    Article  ADS  Google Scholar 

  15. Jutzi, M., Holsapple, K., Wünneman, K. & Michel, P. in Asteroids IV (eds Michel, P. et al.) 679–699 (Univ. Arizona Press, 2015).

  16. Ševeček, P. et al. SPH/N-body simulations of small (D = 10 km) asteroidal breakups and improved parametric relations for Monte-Carlo collisional models. Icarus 296, 239–256 (2017).

    Article  ADS  Google Scholar 

  17. Tillotson, J. H. Metallic Equations of State for Hypervelocity Impact General Atomic Report GA-3216 (General Dynamics, 1962).

  18. von Mises, R. Mechanik der festen Körper in plastisch-deformablen Zustand. Nachr. d. Kgl. Ges. Wiss. Göttingen, Math.-phys. Klasse 4, 582–592 (1913).

    MATH  Google Scholar 

  19. Grady, D. & Kipp, M. Continuum modelling of explosive fracture in oil shale. Int. J. Rock Mech. Min. Sci. 17, 147–157 (1980).

    Article  Google Scholar 

  20. Barnes, J. & Hut, P. A hierarchical O(N log N) force-calculation algorithm. Nature 324, 446–449 (1986).

    Article  ADS  Google Scholar 

  21. Michel, P., Benz, W., Tanga, P. & Richardson, D. C. Collisions and gravitational reaccumulation: forming asteroid families and satellites. Science 294, 1696–1700 (2001).

    Article  ADS  Google Scholar 

  22. Tanga, P., Hestroffer, D., Delbo, M. & Richardson, D. C. Asteroid rotation and shapes from numerical simulations of gravitational re-accumulation. Planet. Space Sci. 57, 193–200 (2009).

    Article  ADS  Google Scholar 

  23. Melosh, H. J. & Ivanov, B. A. Impact crater collapse. Ann. Rev. Earth Planet. Sci. 27, 385–415 (1999).

    Article  ADS  Google Scholar 

  24. Riller, U. et al. Rock fluidization during peak-ring formation of large impact structures. Nature 562, 511–518 (2018).

    Article  ADS  Google Scholar 

  25. Jutzi, M., Asphaug, E., Gillet, P., Barrat, J.-A. & Benz, W. The structure of the asteroid 4 Vesta as revealed by models of planet-scale collisions. Nature 494, 207–210 (2013).

    Article  ADS  Google Scholar 

  26. Wadell, H. Volume, shape and roundness of quartz particles. J. Geol. 43, 250–280 (1935).

    Article  ADS  Google Scholar 

  27. Warner, B. D., Harris, A. W. & Pravec, P. The asteroid lightcurve database. Icarus 202, 134–146 (2009).

    Article  ADS  Google Scholar 

  28. Jehin, E. et al. TRAPPIST: TRAnsiting Planets and PlanetesImals Small Telescope. Messenger 145, 2–6 (2011).

    ADS  Google Scholar 

  29. Pettengill, G. H., Ford, P. G., Johnson, W. T. K., Raney, R. K. & Soderblom, L. A. Magellan: radar performance and data products. Science 252, 260–265 (1991).

    Article  ADS  Google Scholar 

  30. Thomas, P. C. et al. The shape of Gaspra. Icarus 107, 23–36 (1994).

    Article  ADS  Google Scholar 

  31. Hudson, R. S. et al. Asteroid Radar Shape Models, 6489 Golevka PDS ID EAR-A-5-DDR-RADARSHAPE-MODELS-V1.1:RSHAPES-6489GOLEVKA-200006 (NASA PDS, 2000).

  32. Ostro, S. J. et al. Asteroid Radar Shape Models, 1620 Geographos PDS ID EAR-A-5-DDR-RADARSHAPE-MODELS-V1.1:RSHAPES-1620GEOGRAPHOS-200006 (NASA PDS, 2000).

  33. Smith, D. E. et al. Mars Orbiter Laser Altimeter: experiment summary after the first year of global mapping of Mars. J. Geophys. Res. 106, 23689–23722 (2001).

    Article  Google Scholar 

  34. Jorda, L. et al. Asteroid (2867) Steins: shape, topography and global physical properties from OSIRIS observations. Icarus 221, 1089–1100 (2012).

    Article  ADS  Google Scholar 

  35. Preusker, F. et al. Stereo-photogrammetrically derived topography of asteroid (4) Vesta. Proc. American Geophysical Union, Meeting Number 93 abstr. P43E-05 (2012).

  36. Jaumann, R. et al. Vesta’s shape and morphology. Science 336, 687–690 (2012).

    Article  ADS  Google Scholar 

  37. Farnham, T. L. Shape Model of Asteroid 21 Lutetia PDS ID RO-A-OSINAC/OSIWAC-5-LUTETIA-SHAPE-V1.0 (NASA PDS, 2013).

  38. Preusker, F. et al. Topography of Mercury: a global model from MESSENGER orbital stereo mapping. Proc. Ninth Conference European Planetary Science Congress Vol. 9 abstr. EPSC2014-709 (2014).

  39. Preusker, F. et al. Dawn at Ceres—shape model and rotational state. Proc. 47th Lunar and Planetary Science Conference 1954 (LPI, 2016).

  40. Viikinkoski, M. et al. (16) Psyche: a mesosiderite-like asteroid? Astron. Astrophys. 619, L3 (2018).

    Article  ADS  Google Scholar 

  41. Hanuš, J. et al. The shape of (7) Iris as evidence of an ancient large impact? Astron. Astrophys. 624, A121 (2019).

    Article  Google Scholar 

  42. Hiesinger, H. et al. Cratering on Ceres: implications for its crust and evolution. Science 353, aaf4759 (2016).

    Article  ADS  Google Scholar 

  43. Bland, M. T. et al. Composition and structure of the shallow subsurface of Ceres revealed by crater morphology. Nat. Geosci. 9, 538–542 (2016).

    Article  ADS  Google Scholar 

  44. Knezevic, Z. & Milani, A. Proper element catalogs and asteroid families. Astron. Astrophys. 403, 1165–1173 (2003).

    Article  ADS  Google Scholar 

  45. Zappala, V., Cellino, A., Farinella, P. & Milani, A. Asteroid families. II. Extension to unnumbered multiopposition asteroids. Astron. J. 107, 772–801 (1994).

    Article  ADS  Google Scholar 

  46. Ivezic, Ž. et al. Solar System objects observed in the Sloan Digital Sky Survey commissioning data. Astron. J. 122, 2749–2784 (2001).

    Article  ADS  Google Scholar 

  47. Nugent, C. R. et al. NEOWISE Reactivation Mission Year One: preliminary asteroid diameters and albedos. Astrophys. J. 814, 117 (2015).

    Article  ADS  Google Scholar 

  48. Usui, F. et al. Asteroid catalog using AKARI: AKARI/IRC Mid-infrared Asteroid Survey. Pub. Astron. Soc. Jpn 63, 1117–1138 (2011).

    Article  ADS  Google Scholar 

  49. Schäfer, C. et al. A smooth particle hydrodynamics code to model collisions between solid, self-gravitating objects. Astron. Astrophys. 590, A19 (2016).

    Article  Google Scholar 

  50. Collins, G. S., Melosh, H. J. & Ivanov, B. A. Modeling damage and deformation in impact simulations. Met. Planet. Sci. 39, 217–231 (2004).

  51. Silber, E. A., Osinski, G. R., Johnson, B. C. & Grieve, R. A. F. Effect of impact velocity and acoustic fluidization on the simple-to-complex transition of lunar craters. J. Geophys. Res. Planets 122, 800–821 (2017).

    Article  ADS  Google Scholar 

Download references

Acknowledgements

P.V., A.D. and B.C. were supported by CNRS/INSU/PNP. M.Brož was supported by grant 18-04514J of the Czech Science Foundation. J.H. and J.D. were supported by grant 18-09470S of the Czech Science Foundation and by the Charles University Research Programme no. UNCE/SCI/023. This project has received funding from the European Union’s Horizon 2020 research and innovation programmes under grant agreement nos 730890 and 687378. This material reflects only the authors’ views, and the European Commission is not liable for any use that may be made of the information contained herein. TRAPPIST-North is a project funded by the University of Liège, in collaboration with Cadi Ayyad University of Marrakech (Morocco). TRAPPIST-South is a project funded by the Belgian Fonds (National) de la Recherche Scientifique (F.R.S.-FNRS) under grant FRFC 2.5.594.09.F. E.J. and M.G. are F.R.S.-FNRS Senior Research Associates.

Author information

Authors and Affiliations

Authors

Contributions

P.V. designed the research. P.V., M.M., R.F. and T.F. reduced and deconvolved the SPHERE images. M.V. and J.H. reconstructed the 3D shape of Hygiea. L.J. and P.V. performed the analysis of Hygiea’s shape. P.Š. and M.Brož ran the SPH simulations. M.F. and E.J. acquired and reduced the TRAPPIST data. M.M. and L.J. produced the albedo map. P.V. and F.D. served as principal investigators to acquire the near-infrared spectral data. B.C. provided the mass estimate. P.V., L.J., P.Š. and M.Brož worked jointly to write the manuscript. All authors discussed the results and commented on the manuscript.

Corresponding author

Correspondence to P. Vernazza.

Ethics declarations

Competing interests

The authors declare no competing interests.

Additional information

Peer review information Nature Astronomy thanks Derek Richardson and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Supplementary information

Rights and permissions

Reprints and permissions

About this article

Check for updates. Verify currency and authenticity via CrossMark

Cite this article

Vernazza, P., Jorda, L., Ševeček, P. et al. A basin-free spherical shape as an outcome of a giant impact on asteroid Hygiea. Nat Astron 4, 136–141 (2020). https://doi.org/10.1038/s41550-019-0915-8

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI: https://doi.org/10.1038/s41550-019-0915-8

This article is cited by

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