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Volume 60 Supplement 1

Special Issue: Itokawa-Hayabusa and beyond

Size-frequency statistics of boulders on global surface of asteroid 25143 Itokawa

Earth, Planets and Space volume 60, pages 13–20 (2008)Cite this article

Abstract

The surface of asteroid 25143 Itokawa is covered with numerous boulders although gravity is very small compared with that of other asteroids previously observed from spacecraft. Here we report the size-frequency statistics of boulders on the entire surface of Itokawa based on high-resolution images (1 pixel ≈0.4 m) obtained by the Hayabusa spacecraft. There are 373 boulders larger than 5 m in mean horizontal dimension on the entire surface—0.393 km2—and the number density is nearly 103/km2. The cumulative boulder size distribution on the entire surface has a power-index of −3.1 ± 0.1. For the east and west sides and the head and body portions of Itokawa, the power-index of the size distributions and the number densities of boulders of these areas are thought to be similar from the statistical point of view. A global mapping of boulders shows that there is no apparent correlation in the locations of boulders and craters. The ratio of the total volume of the boulders to the total excavated volume of the craters on Itokawa is ≈25% when only craters larger than 50 m in mean diameter are considered, and this ratio is extremely larger than that on Eros and the Moon, respectively. The origin of boulders on the surface of Itokawa was examined quantitatively by calculating the number of boulders and the size of the largest boulder using a model based on impact cratering experiments. The result indicated that the boulders on the surface of Itokawa cannot solely be the product of craters. Our results suggest that the boulders originated from the disruption of the larger parent body of Itokawa, as has been described in previous papers (Fujiwata et al., Science, 312, 1330–1334, 2006; Saito et al., Science, 312, 1341–1344, 2006).

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Authors and Affiliations

  1. Fukushima National College of Technology, Iwaki, Fukushima, 970-8034, Japan

    Tatsuhiro Michikami

  2. Graduate School of Science, Kobe University, Kobe, Japan

    Akiko M. Nakamura, Takayuki Honda & Kensuke Hiraoka

  3. University of Aizu, Aizu-Wakamatsu, Fukushima, Japan

    Naru Hirata & Hirohide Demura

  4. Planetary Science Institute, Tucson, Arizona, USA

    Robert W. Gaskell

  5. National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki, Japan

    Ryosuke Nakamura

  6. Institute of Space and Astronautical Science, Japanese Aerospace Exploration Agency, Kanagawa, Japan

    Chikatoshi Honda

  7. PASCO Corporation, Meguro-ku, Tokyo, Japan

    Jun Saito

  8. Seoul National University, Seoul, Korea

    Masateru Ishiguro

  9. The University Museum, University of Tokyo, Tokyo, Japan

    Hideaki Miyamoto

Authors
  1. Tatsuhiro Michikami
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  2. Akiko M. Nakamura
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  3. Naru Hirata
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  4. Robert W. Gaskell
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  5. Ryosuke Nakamura
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  6. Takayuki Honda
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  7. Chikatoshi Honda
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  8. Kensuke Hiraoka
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  9. Jun Saito
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  10. Hirohide Demura
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  11. Masateru Ishiguro
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  12. Hideaki Miyamoto
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Correspondence to Tatsuhiro Michikami.

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Michikami, T., Nakamura, A.M., Hirata, N. et al. Size-frequency statistics of boulders on global surface of asteroid 25143 Itokawa. Earth Planet Sp 60, 13–20 (2008). https://doi.org/10.1186/BF03352757

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  • DOI: https://doi.org/10.1186/BF03352757

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