Glycine's Radiolytic Destruction in Ices: First In-Situ Laboratory Measurements for Mars

Abstract

We report new laboratory studies of the radiation-induced destruction of glycine-containing ices for a range of temperatures and compositions that allow extrapolation to Martian conditions. In-situ infrared spectroscopy was used to study glycine decay rates as a function of temperature (from 15 to 280 K) and initial glycine concentrations in six mixtures whose compositions ranged from dry glycine to H$_2$O + glycine (300:1). Results are presented in several systems of units, with cautions concerning their use. The half-life of glycine under the surface of Mars is estimated as an extrapolation of this data set to Martian conditions, and trends in decay rates are described as are applications to Mars's near-surface chemistry.