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A common mass scaling for satellite systems of gaseous planets

Naturevolume 441pages834839 (2006) | Download Citation



The Solar System's outer planets that contain hydrogen gas all host systems of multiple moons, which notably each contain a similar fraction of their respective planet's mass (10-4). This mass fraction is two to three orders of magnitude smaller than that of the largest satellites of the solid planets (such as the Earth's Moon), and its common value for gas planets has been puzzling. Here we model satellite growth and loss as a forming giant planet accumulates gas and rock-ice solids from solar orbit. We find that the mass fraction of its satellite system is regulated to 10-4 by a balance of two competing processes: the supply of inflowing material to the satellites, and satellite loss through orbital decay driven by the gas. We show that the overall properties of the satellite systems of Jupiter, Saturn and Uranus arise naturally, and suggest that similar processes could limit the largest moons of extrasolar Jupiter-mass planets to Moon-to-Mars size.

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This research was supported by NASA's Planetary Geology and Geophysics and Outer Planets Research programmes. Computer resources and support were provided by SwRI. We thank L. Dones, R. Mihran and S. Peale for comments.

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  1. Space Studies Department, Southwest Research Institute, Boulder, Colorado, 80302, USA

    • Robin M. Canup
    •  & William R. Ward


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Reprints and permissions information is available at The authors declare no competing financial interests.

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Correspondence to Robin M. Canup.

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    This file contains Supplementary Methods, Supplementary Notes and Supplementary Figures 1 and 2. (PDF 53 kb)

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