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Secondary craters on Europa and implications for cratered surfaces

Nature volume 437, pages 1125–1127 (2005)Cite this article

Abstract

For several decades, most planetary researchers have regarded the impact crater populations on solid-surfaced planets and smaller bodies as predominantly reflecting the direct (‘primary’) impacts of asteroids and comets1. Estimates of the relative and absolute ages of geological units on these objects have been based on this assumption2. Here we present an analysis of the comparatively sparse crater population on Jupiter's icy moon Europa and suggest that this assumption is incorrect for small craters. We find that ‘secondaries’ (craters formed by material ejected from large primary impact craters) comprise about 95 per cent of the small craters (diameters less than 1 km) on Europa. We therefore conclude that large primary impacts into a solid surface (for example, ice or rock) produce far more secondaries than previously believed, implying that the small crater populations on the Moon, Mars and other large bodies must be dominated by secondaries. Moreover, our results indicate that there have been few small comets (less than 100 m diameter) passing through the jovian system in recent times, consistent with dynamical simulations3,4,5,6.

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Figure 1: A sample region on Europa that demonstrates the extreme ‘clusteredness’ of Europa's small craters.
Figure 2: A comparison of europan and lunar crater size–frequency distributions, demonstrating that lunar secondaries could account for most of the observed small lunar craters.

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Acknowledgements

E.B.B. was previously at the University of Colorado at Boulder and Southwest Research Institute, Boulder. NASA's Galileo and JSDAP programs funded the research reported here. We thank B. Ivanov for providing comments that improved the clarity and structure of this manuscript.

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Authors and Affiliations

  1. Lockheed Martin, Space Exploration Systems, MS S8110, PO Box 179, Colorado, 80201, Denver, USA

    Edward B. Bierhaus

  2. Southwest Research Institute, 1050 Walnut Street, Suite 400, Colorado, 80302, Boulder, USA

    Clark R. Chapman & William J. Merline

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  1. Edward B. Bierhaus
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  2. Clark R. Chapman
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  3. William J. Merline
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Correspondence to Edward B. Bierhaus.

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Bierhaus, E., Chapman, C. & Merline, W. Secondary craters on Europa and implications for cratered surfaces. Nature 437, 1125–1127 (2005). https://doi.org/10.1038/nature04069

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