Home Page Science Frontiers

No. 89: Sep-Oct 1993

Issue Contents

Other pages

Other Interesting Sites











Blasting Rocks Off Planets

"Can rocks from the surface of a major planet or satellite be launched into interplanetary space by natural processes? A few years ago the answer to this question would have been a resounding "no" from the experts on both volcanism and impact cratering, the only geological processes known to eject solid material at substantial velocities. Observation, however, has once again confounded expectation."

In the snowy wastes of Antarctica, scientists have picked up meteorites that almost certainly came from the moon and Mars. And near St. Gallen, Switzerland, there was discovered a 22-centimeter block of Malm limestone that was apparently ejected from the Ries impact crater, almost 200 kilometers away, about 15 million years ago. We know all of these rocks are impact debris because they contain shatter cones indicating a violent origin.

Not only did these bits of debris confound expectations, but their shatter cones implied shock-wave pressures far too low to achieve lunar and Martian escape velocities, or even the velocity necessary to propel that chunk of Malm limestone 200 kilometers. Something was wrong somewhere.

It has turned out that shock-wave theory had been misapplied. It is not the pressure that is important in ejecting bits of debris from around the impact site, but rather it is the pressure gradient. Anomaly extirpated!

(Melosh, H.J.; "Blasting Rocks Off Planets," Nature, 363:498, 1993.)

Moral. A.C. Clarke was right again: When a respected scientist says something cannot happen, it probably will!

From Science Frontiers #89, SEP-OCT 1993. 1993-2000 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