Radiation chemistry of a multicomponent aqueous system relevant to chemistry of cometary nuclei

• Published in: Journal of molecular evolution Vol. 22; no. 2; pp. 175 - 187
• Main Authors: DRAGANIC, Z. D, VUJOSEVIC, S. I, NEGRON-MENDOZA, A, AZAMAR, J. A, DRAGANIC, I. G
• Format: Journal Article
• Language: English
• Published: New York, NY Springer 01-01-1985
• Subjects: Chemistry; Chemistry, Organic; Exact sciences and technology; Freezing; Inorganic chemistry and origins of life; Kinetics; Organic Chemistry Phenomena; Origins of life; Radiation; Space life sciences; Spectrophotometry, Infrared; Temperature; Water; Gamma irradiation; Hydrogen Cyanides; Origin of life; Formic acid; Acetonitrile; Cometary nucleus; Radiolysis; Chemical composition; Aqueous solution; Methanol
• ISSN: 0022-2844; 1432-1432
• DOI: 10.1007/BF02101695

We have examined a water-dominated multicomponent system after irradiation in the multimegarad dose range with gamma rays from a 60Co source at both 77 and 310 K. The constituents were simple organic compounds in the proportions in which they appear in a dense interstellar cloud: HCN/CH3OH/CH3CN/C2H5CN/HCOOH = 1:0.6:0.2:0.1:0.05. The total amounts were adjusted to correspond to a carbon to nitrogen ratio of 1.8 and a water content of about 50% in a cometary nucleus where the dust to volatiles ratio is 1; the total amount of CN-bearing compounds was taken to correspond to 0.4% of the cometary mass. In experiments at 310 K about 40 radiolytic products are identified, among them aldehydes and amino and carboxylic acids. Abundant polymeric material (Mw up to 80,000 daltons) is formed. The basic aspects of radiolysis of the liquid system are present also at 77 K, although at radiation-chemical yields that are lower by one to two orders of magnitude. We have considered the relevance of the present findings to the chemistry of a liquid-water core and the icy layers of a cometary nucleus.