The Radiation Stability of Thymine in Solid H₂O

Nucleobases are of significant importance to all known organisms, may be an important building block of life, and could be important biosignatures of current or past life. Given their potential significance to the field of astrobiology, it is important to understand the survival of these molecules when subjected to ionizing radiation as is present in a range of extraterrestrial environments. In this work, we present data on the kinetics of the radiolytic destruction of pure thymine and water + thymine ice mixtures at temperatures from 13 to 150 K. Rate constants were measured using in situ infrared spectroscopy, and radiolytic half-lives for thymine were computed for different planetary and interstellar environments. Our results demonstrate that the survival of thymine decreases as the dilution of thymine in water increases. Additionally, we find that thymine survival increases with ice temperature and that this decrease may be related to structure of the ice matrix.