Home Page Science Frontiers

No. 111: May-Jun 1997

Issue Contents

Other pages

Other Interesting Sites











Extraterrestrial Handedness

Human life forms favor right-handedness over left-handedness by a 9:1 ratio. Other terrestrial animals are also asymmetrical in various ways. But on the molecular level, terrestrial biochemistry is all left-handed. As far as scientists can determine, only left-handed amino acids are incorporated into proteins. In nonlife (if such a state really exists), amino-acid molecules are right- and lefthanded in equal numbers -- as least this has been the theory up until now.

Amino acids are found in substances we assume are non-life or of abiotic origin. In fact, amino acids are present in meteorites, often in substantial amounts. They are profuse in Australia's Murchison meteorite, a carbonaceous chondrite. However, analysis of the Murchison's amino acids indicates that there are slightly more (7-9%) left-handed than right-handed amino acids present.

This extraterrestrial handedness is of great import to both cosmologists and biologists, because the carbonaceous chondrites are thought to have formed 4.5 billion years ago -- long before life on earth originated. Furthermore, some of the Murchison's amino acids have never been found in terrestrial life, and they are also slightly left-handed. For some unfathomed reason, chemical and biological evolution both tilt to the left!

(Bada, Jeffrey L.; "Extraterrestrial Handedness?" Science, 275:942, 1997. Cronin, John R., and Pizzarello, Sandra; "Enantiomeric Excesses in Meteoritic Amino Acids," Science, 275:951, 1997. Also: Peterson, I.; "Left-Handed Excess in Meteorite Molecules," Science News, 151:118, 1997. Note that left-handed amino acids in the Murchison meteorite were also reported in the early 1980s: Kerr, Richard A.; "Odd Amino Acids in a Meteorite," Science, 216:972, 1982.)

Comments. This discovery of a tilted universe means that we cannot confirm Martian life with spacecraft instruments that test for an excess of left-handed amino acids.

Human philosophers, from the ancient Greeks to the present, like to think the universe is in balance, that equality reigns, yin and yang, and similar presumptions. But, let's face it: our particular universe is lopsided. Of course, our universe may be balanced by another one far away, where everything, including its intelligent life forms, are made from right-handed amino acids -- chemically speaking, a mirror image of our universe. Balance could thus be preserved at that scale.

From Science Frontiers #111, MAY-JUN 1997. 1997-2000 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