Polarized Starlight and the Handedness of Life

One of the mysteries of life is why organisms on our planet uses L-amino acids exclusively, when their mirror images have the same chemical stability. Back in February, 1997, "Hal's Pick" was an article from Science about the enantiomeric excesses in the amino acids of the Murchison meteorite, and the theory that the preference for left-handed amino acids that pervades life on earth arose from such an extraterrestrial template. Interesting as that article was, the attribution of the preference to meteorites just pushes the question back one level. The next logical thing to ask is, "How could meteorites have been depleted in one or enriched in the other isomer?" Stuart Clark and his colleagues at the University of Hertfordshire have found circularly polarized light (that could preferentially photolyze one isomer type) in the star-forming regions of some galaxies. They believe that it is the result of the scattering of unpolarized light by particles that have been aligned by the magnetic field of a nearby star. The amount of circular polarization in parts of the Orion nebula has been measured at almost 20%!

Pick Attribution: 

Stuart Clark

Publication Date: 
Friday, April 13, 2012