Skip to main content

Thank you for visiting 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.

The Moon may be a Former Planet


Certain peculiarities of the orbit of Mercury may be explained if there was once a planet between Mercury and Venus. But this orbit would have been unstable, and the hypothetical planet could have been captured by the Earth.

This is a preview of subscription content

Access options

Rent or Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.


  1. 1

    Kuiper, G. P., in Astrophysics (edit. by Hynek, J. A.), 357 (McGraw-Hill, 1951).

    Google Scholar 

  2. 2

    Allen, C. W., Astrophysical Quantities, second ed. (Univ. London, Athlone Press, 1963).

    Google Scholar 

  3. 3

    Poincaré, H., Les Méthodes Nouvelles de la Mecanique Celeste, 3, 141 (1899).

    ADS  Google Scholar 

  4. 4

    Hill, C. W., Amer. J. Math., 1, 5 (1878).

    MathSciNet  Article  Google Scholar 

  5. 5

    Szebehely, V. G., Theory of Orbits (Academic Press, 1967).

    MATH  Google Scholar 

  6. 6

    Stockwell, J. N., Smithsonian Contributions to Knowledge, 18, 9 (1873).

    Google Scholar 

  7. 7

    Urey, H. C., in Physics and Astronomy of the Moon (edit. by Kopal, Z.) (Academic Press, 1962).

    Google Scholar 

  8. 8

    Baldwin, R. B., A Fundamental Survey of the Moon (McGraw-Hill, 1965).

    Google Scholar 

  9. 9

    Munk, W. H., and MacDonald, G. J. F., The Rotation of the Earth (Cambridge Univ. Press, 1960).

    MATH  Google Scholar 

  10. 10

    MacDonald, G. J. F., in The Earth–Moon System (edit. by Marsden, B. G., and Cameron, A. G. W.), 165 (Plenum Press, 1966).

    Book  Google Scholar 

  11. 11

    Gerstenkorn, H., Z. Astrophys., 36, 258 (1955).

    Google Scholar 

  12. 12

    Gold, T., in The Earth–Moon System (edit. by Marsden, B. G., and Cameron, A. G. W.), 96 (Plenum Press, 1966); Cameron, A. G. W., ibid. 263 (Plenum Press, 1966).

    Google Scholar 

Download references

Author information



Rights and permissions

Reprints and Permissions

About this article

Cite this article

BAILEY, J. The Moon may be a Former Planet. Nature 223, 251–253 (1969).

Download citation

Further reading


By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.


Quick links