Computational study of radiation chemical processing in comet nuclei

Abstract

Cometary nuclei have been exposed to high levels of ionizing radiation since their formation. We present here some results of a computer model calculation of the effect of ionizing radiation on cometary material. The external (cosmic rays) and internal (embedded radionuclides) contributions in the processing of cometary nuclei are considered. As a first approximation we have used the available kinetic data of the liquid water system to model the radiation effects in a frozen cometary environment. Our [correction of out] data suggest that massive radiation chemical processing due to cosmic rays may have taken place only in the outer layers of comets. The internal contribution of radionuclides to the radiation processing of comet cores seems to be modest. Therefore, comets could be carriers of intact homochiral biomolecules.

Comets: Potential Sources of Prebiotic Molecules for the Early Earth

“…May chemistry inside the nucleus have altered the pristine composition of comets since their accretion? Navarro-Gonzalez et al, (1992) and NavarroGonzalez and Romero (1996) have studied theoretically the effect of ionizing radiation (cosmic rays and embedded radionuclides) on the cometary material and conclude that pristine organic compounds should not be altered except in the external layers of the comet. It is also predicted that an original enantiomeric excess of alanine would not be destroyed by radioracemisation during the decay of radionuclides.…”