The Effect of Radiogenic Heating on the Amino Acid Content of an Early Cometary Body

Abstract

This study compares the rates for the formation and destruction of amino acids in the liquid cometary core subjected to radiogenic heating by the β + decay of the cosmogenic nuclide 26 Al . The evolution of the temperature and mass of the comet were computed along with the dynamics of relatively complex organic species such as amino acids. Given the experimentally determined rate coefficient for the radiolysis of amino acids in water solution, the destruction of amino acids is virtually completed after an absorbed radiation dose of ~1 kGy . The calculations suggest that the liquid water core in comets with an initial radionuclide abundance that is sufficient to crystallize and melt the original amorphous ice is subjected to a dose of 100 - 1500 kGy . Any amino acid concentration formed in water either by radiolysis of simpler compounds or by thermal processes such as the synthesis of Strecker could not survive the irradiation delivered by the decay of 26 Al .