062 I Scientific Highlights Half

a century ago it was demonstrated by Miller [1] and Urey that at least some of the 20 amino acids on which we depend for life could be produced in a spark discharge in a chemical environment that may have existed early in the Earth’s history. Thus the model of such an environment in a lightning storm became the accepted means for producing amino acids on Earth. However, the amino acids have been found to have a left-handed chirality, whereas the Miller-Urey mechanism produces equal numbers of left- and right-handed molecules. Furthermore, amino acids have been found in meteorites[2], and those that have a preferred chirality had more lefthanded molecules than right-handed molecules (at a level of 10%). Several mechanisms have been suggested as being the means by which the amin