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No. 61: Jan-Feb 1989

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Celestial burlesque?

Astronomers have long wondered about Mercury. Its density (5.44) is unusually high for such a small planet, and its orbit's inclination (7) and eccentricity (0.206) are also anomalously high. In one blow. W. Benz, A.G.W. Cameron, and W. Slattery may have solved all three problems.
Computer simulation of proto-Mercury being stripped of its lighter, outer crust by a collision
Four frames from a computer simulation of proto-Mercury being stripped of its lighter, outer crust by a collision. Frame times are -1, +2.3, +7.7, and +41.7 minutes after impact. The dark molten sheet of iron in Frame #4 will collapse into a sphere, while the silicates will escape Mercury's gravitational pull.

They think Mercury's original, lighter, silicate outer layers were stripped off during the impact of one of the small protoplanets that are thought to have swirled around the inner solar system shortly after its formation. Computations on a supercomputer revealed to these three researchers that, if the protoplanet had hit Mercury at between 20 and 30 kilometers/second, then its dense iron core would have survived pretty much intact. A lower velocity would not have stripped off the lighter outer layers; anything higher would have blasted the whole planet into smithereens.

Calculations of this type also suggest that if a protoplanet the size of Mars had hit protoearth, it likewise would have stripped off its light silicate mantle. After this material that had been torn off gravitationally sphericized itself in orbit around the earth, it became--you guessed it - our moon.

(Stewart, Glen R.; "A Violent Birth for Mercury," Nature, 335:496, 1988. Also: Anonymous; "Mercury Stripped by Blow from Meteorite," New Scientist, November 5, 1988.)

Comment. It seems that our early solar system was somewhat Velikovskian in character, with many celestial missiles flying about. But that was long ago - or was it?

Reference. Mercury's idosyncracies are cataloged in Chapter AH in our catalog: The Moon and the Planets. For information about this book, visit: here.

From Science Frontiers #61, JAN-FEB 1989. 1989-2000 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