CHEMICAL EVOLUTION IN SPACE- A SOURCE OF PREBIOTIC MOLECULES

In laboratory Astrophysics at Laiden University a laboratory analog for following the chemical evolution of interstellar dust in space shows that the dust contains the bulk of organic material in the universe. We follow the photoprocessing of low temperature (10 K) mixtures of ices subjected to vacuum ultraviolet radiation in simulation of interstellar conditions. ‘Ihe mOst important, but necessary, difference is in the time scales for photo-processing. One hour in the laboratory Is equivalent to one thousand years in low density regions of space and as much as, or greater than, ten thousand to one million years in the depths of dense molecular clouds. The ultimate product of photoprocessing of grain material In the laboratory is a complex nonvolatile residue which is yellow in color and soluble in water and methanol. The molecular weight is greater than the mid-hundreds. The infrared absorption spectra indicate the presence of carboxylic acid and amino groups resembling those of other molecules of presumably preblological significance produced by more clas-sical mthods. One of our residues, when subjected to high resolution mass spectroscopy gave a mask of 82 corresponding to C4R6h2 after release of CO2 and trace ammomts of urea suggesting amino pyroline rings. The deposit of prebfotic dust molecules occurred as many as 5 timas in the first 500-700 million yearn on a primitive Earth by accretion during the paaaage of the solar system through a den e b interstellar cloud. The deposition rate during each paaaage is.estimated to be between 10 and lOlo total deposition of 10 ’- g pf6 y ear during the million or so years of each passage; i.e. a 10 metric tons of complex organic arterial per passage