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Hyperion's sponge-like appearance

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Abstract

Hyperion is Saturn’s largest known irregularly shaped satellite and the only moon observed to undergo chaotic rotation1,2,3. Previous work has identified Hyperion’s surface as distinct from other small icy objects4,5 but left the causes unsettled. Here we report high-resolution images that reveal a unique sponge-like appearance at scales of a few kilometres. Mapping shows a high surface density of relatively well-preserved craters two to ten kilometres across. We have also determined Hyperion’s size and mass, and calculated the mean density as 544 ± 50 kg m-3, which indicates a porosity of >40 per cent. The high porosity may enhance preservation of craters by minimizing the amount of ejecta produced or retained6,7, and accordingly may be the crucial factor in crafting this unusual surface.

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Figure 1: Surface features of Hyperion.
Figure 2: Impact crater characteristics and conditions on Hyperion.

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Acknowledgements

Technical assistance was provided by B. Carcich, K. Consroe, P. Smith and P. F. Helfenstein. G. Patton checked the crater tabulation on Phoebe and Hyperion. This work was funded in part by the Cassini project. A portion of this work was done at the Jet Propulsion Laboratory, California Institute of Technology, under a contract from NASA. The work of L.I., P.T. and L.S. was funded in part by the Italian Space Agency. The manuscript benefited from reviews by K. Housen and E. Asphaug.

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Authors and Affiliations

  1. Center for Radiophysics and Space Research, Cornell University, Ithaca, New York 14853, USA,

    P. C. Thomas, J. A. Burns, P. Helfenstein, J. Richardson & J. Veverka

  2. Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California 91109, USA,

    J. W. Armstrong, S. W. Asmar, T. V. Johnson & N. Rappaport

  3. Institut für Geologische Wissenschaften, Freie Universität, 12249 Berlin, Germany,

    T. Denk

  4. Institute of Planetary Research, German Aerospace Center, Rutherfordstrasse 2, 12489 Berlin, Germany,

    B. Giese

  5. Dipartimento di Ingegneria Aerospaziale ed Astronautica, Università La Sapienza, via Eudossiana 18, 00184 Roma, Italy,

    L. Iess & L. Somenzi

  6. Department of Planetary Sciences, University of Arizona, Tucson, Arizona 85721, USA,

    A. McEwen

  7. Physics and Astronomy Department, University of California at Los Angeles, Box 951547 Los Angeles, California 90095, USA,

    L. Nicolaisen

  8. Space Science Institute, 4750 Walnut Street, Boulder, Colorado 80301, USA,

    C. Porco

  9. DIEM-II Facoltà di Ingegneria, Università di Bologna, Via Fontanelle, 4047100 Forlì, Italy,

    P. Tortora

  10. Johns Hopkins University Applied Physics Laboratory, 11100 Johns Hopkins Road, Laurel, Maryland 20723, USA,

    E. P. Turtle

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  1. P. C. Thomas
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  2. J. W. Armstrong
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  4. J. A. Burns
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  7. P. Helfenstein
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  8. L. Iess
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  9. T. V. Johnson
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  10. A. McEwen
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  11. L. Nicolaisen
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  12. C. Porco
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  13. N. Rappaport
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  14. J. Richardson
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  15. L. Somenzi
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  16. P. Tortora
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  17. E. P. Turtle
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  18. J. Veverka
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Corresponding author

Correspondence to P. C. Thomas.

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Reprints and permissions information is available at www.nature.com/reprints. The authors declare no competing financial interests.

Supplementary information

Supplementary Table S1

This file contains Supplementary Table S1 which summarizes instantaneous spin pole solutions for Hyperion derived from control points measured in Cassini images. (PDF 38 kb)

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Thomas, P., Armstrong, J., Asmar, S. et al. Hyperion's sponge-like appearance. Nature 448, 50–53 (2007). https://doi.org/10.1038/nature05779

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