The moon

, Volume 4, Issue 1–2, pp 28–34 | Cite as

Moments of inertia of the lunar globe, and their bearing on chemical differentiation of its outer layers

  • Zdeněk Kopal


It is pointed out that the observed moments of inertia of the Moon, disclosed by its librations, are influenced mainly by the distribution of mass in the outer zone in which the lithostatic pressure is less than 10 kb (i.e., in the outer shell not more than 200 km deep); and a conspicuous departure of such moments from those expected in hydrostatic equilibrium disclosed that these layers could never have been fluid. In the same way, the actual shape of the lunar surface cannot represent a solidified surface of a fluid, petrified at any distance from the Earth.

The shape of the Moon, and differences of its moments of inertia must reflect the way in which the initial process of cold accretion fell short of producing a globe with strictly spherically-symmetrical stratification of material; and has nothing to do with tides - present or fossil. Such melting or lava flows as may have occurred at the Moon's surface from time to time must have remained localized, and without much effect on the dynamical properties of the Moon. A global ocean of molten magma some 200 km in depth (postulated sometimes to provide a reservoir in which the differentiation of elements exhibited by surface rocks could have taken place) at any time in the past is incompatible with the dynamical evidence on the motion of the Moon about its center of gravity.


Stratification Outer Layer Dynamical Property Lava Flow Outer Shell 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.


Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.


  1. Brown, E. W.: 1919, inTables of the Motion of the Moon, Yale Univ. Press, New Haven, Conn.Google Scholar
  2. Eigen, J. M. and Hathaway, J. D.: 1967, inMeasure of the Moon (ed. by Z. Kopal and C. L. Goudas), D. Reidel Publ. Co., Dordrecht, Holland; pp. 305–316.Google Scholar
  3. Gorynia, A. A.: 1965, Nauch. Dumka, Ser. Astron.-Astrofiz., Kiev.Google Scholar
  4. Habibullin, Sh. T.: 1966, Trudy Astron. Inst. Univ. Kazan, No. 34.Google Scholar
  5. Jeffreys, H.: 1924, inThe Earth (and later editions) Chapter 4.Google Scholar
  6. Kopal, Z.: 1969,The Moon (sec. edition), D. Reidel Publ. Co., Dordrecht, Holland.Google Scholar
  7. Koziel, K.: 1967a,Icarus 7, 1.Google Scholar
  8. Koziel, K.: 1967b, inMeasure of the Moon, (ed. by Z. Kopal and C. L. Goudas), D. Reidel Publ. Co., Dordrecht, Holland; pp. 3–11.Google Scholar
  9. Latham, G. V., Ewing, M., Press, F., Sutton, G., Dorman, J., Nakamura, Y., Toksoz, N., Lammlein, D., and Duennebier., F.:The Moon 4, in press.Google Scholar
  10. Meyer, D. L. and Ruffin, B. W.: 1965,Icarus 4, 513.Google Scholar
  11. Mills, G. A.: 1967,Icarus 6, 131; and7, 193.Google Scholar
  12. Mills, G. A.: 1968,Icarus 8, 90.Google Scholar
  13. Mills, G. A. and Sudbury, P. V.: 1968,Icarus 9, 538.Google Scholar
  14. Turkevich, A.: 1971, private communication at the NATO Summer Institute on the Moon, Patras, Greece.Google Scholar
  15. Wollenhaupt, W. R. and Sjogren, W. L.: 1972,The Moon 4, in press.Google Scholar

Copyright information

© D. Reidel Publishing Company 1972

Authors and Affiliations

  • Zdeněk Kopal
    • 1
  1. 1.The Lunar Science InstituteHoustonUSA

Personalised recommendations