Home Page Science Frontiers

No. 78: Nov-Dec 1991

Issue Contents

Other pages

Other Interesting Sites











Meteoroid impacts: the other side of the story

Astronomers have long puzzled over the origin of localized magnetic anomalies on the moon. These magnetic concentrations (called "magcons") are located precisely on the opposite side of the moon from the larger lunar basins. How could an impact on the moon magnetize the antipodal region?

The impact of a large silicate meteoroid at speeds of 10 kilometers/second would not only blast out a big crater but it would also create a huge cloud of hot, partially ionized gas. This hot gas or plasma will conduct electricity and interact with lunar magnetic fields. As the plasma cloud spreads away from the impact site, it acts like a bulldozer, compressing the lunar magnetic fields ahead of it, as it envelopes the whole moon and rushes towards the antipodal point. It drives the compressed mag netic field into the surface, permanently magnetizing the rocks at the antipodal point. Voila! Magcons. (Hood, L.L., and Huang, Z.; "Formation of Magnetic Anomalies Antipodal to Lunar Impact Basins: Two-Dimensional Model Calculations," Journal of Geophysical Research, 96:9837, 1991.)

Comment. The earth also sports scars from the impacts of large meteoroids. Are there magnetic anomalies opposite these craters? Even more interesting to check out would be the holes blasted in the earth's biosphere by the converging masses of hot gases at the an tipodal points. Wouldn't there be extinctions seen in the fossil record at these antipodal points?

Reference. Magcons are cataloged as ALZ1 in The Moon and Planets. This catalog is described here.

From Science Frontiers #78, NOV-DEC 1991. 1991-2000 William R. Corliss

Science Frontiers Sourcebook Project Reviewed in:


  • "A sourcebook of unexplained phenomena is therefore a valuable addition to a collection of scientific literature. William R. Corliss has provided this in the past with his source books of scientific anomalies in several subjects, and now he has provided it for astronomy. He has done an excellent job of collecting and editing a large amount of material, taken in part from scientific journals and in part from scientific reporting in the popular or semi-scientific press." -- "The Mysterious Universe: A Handbook of Astronomical Anomalies", reviwed by Thomas Gold, Cornell University, in Icarus, vol.41, 1980

  • "An interesting, systematic presentation of unusual weather [..] This book is recommended for a general audience" --"Corliss, William R., Tornados, Dark Days, Anomalous Precipitation, and Related Weather Phenomena, Sourcebook Project, 1983.", revieweed in Choice, September 1983
  • "..the science is necessarily somewhat speculative, but Corliss's symthesis is based on reputable sources." -- "Corliss, William R. (Compiler). Lightning, Auroras, Nocturnal Lights, and Related Luminous Phenomena" reviwed by Joseph M. Moran, Univ. of Wisconsin in Science Books and Films, Sep/Oct 1983

  • "Before opening the book, I set certain standards that a volume which treads into dangerous grounds grounds like this must meet. The author scrupulously met, or even exceeded those standards. Each phenomenon is exhaustively documented, with references to scientific journals [..] and extensive quotations" -- "Book Review: The moon and planets: a catalog of astronomical anomalies", The Sourcebook Project, 1985., Corliss, W. R., Journal of the Royal Astronomical Society of Canada, Vol. 81, no. 1 (1987), p. 24., 02/1987