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No. 16: Summer 1981

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Grooves Of Phobos Still Unexplained

The Martian satellite Phobos is etched by curious grooves. Initially, the grooves were thought to be fracture lines formed by the impact that blasted out Stickney, the huge crater seen on Phobos. However, studies of the grooves revealed at least three families of grooves of different ages, with members of each family located on parallel planes cutting right through the body of the satellite.

Two recent papers have proposed radically different explanations. A. Horvath and E. Illes wonder whether Phobos might not be a layered structure, having once been part of a larger stratified body. J.B. Murray thinks the families of grooves might have been scraped out by disciplined formations of meteorites that were launched into space by Martian volcanos.

(Horvath, A., and Illes, E.; "On the Possibility of the Layered Structure of Phobos," Eos, 62:203, 1981. Also: Murray, J.B.; "Grooved Terrains on Planetary Satellites," Eos, 62:202, 1981.)

Comment. It is not easy to conceive of such well-drilled formations of meteorites. Neither is it easy to imagine a large, stratified body that might have given rise to Phobos.

From Science Frontiers #16, Summer 1981. 1981-2000 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