Abstract Organic molecules formed within interstellar dust grain ice mantles may have contributed to the pre-biogenic organic inventory of the early Earth. Their ability to remain on the grain following mantle sublimation is likely to have been an important factor. Glycine, alanine, glutamic acid and aspartic acid were deposited on hydrogenated and dehydrogenated amorphous MgSiO3 particles and characterised by infrared spectroscopy and synchrotron X-ray powder diffraction. In situ synchrotron X-ray powder diffraction was subsequently used to monitor the loss of the amino acids from the silicates as a function of temperature. Only glycine and alanine were found to deposit on the amorphous silicate particles, evidenced by characteristic infrared bands and diffraction features. Glycine deposited as mixed phases, while D- and L-alanine deposited as single phases. A number of peptide and other phases of astronomical and astrobiological interest were also observed. Glycine was lost from the silicate at temperatures below the melting/degradation temperature of pure glycine, with ∼15 ○C difference between the hydrogenated and dehydrogenated silicates. Alanine survived to temperatures well above its melting point, but with clear temperature differences between L- and D- forms. Not all amino acids that potentially form under interstellar conditions appear able to transfer to bare silicate surfaces during ice mantle loss under warm early solar nebula/disk conditions. This could point to a possible astromineralogical selection mechanism that may have influenced the specific species, their relative proportion and therefore the contributions that pre-solar organics delivered by pre-solar dust may have made to the Earth’s original organic inventory.
Thompson et al. (Wed,) studied this question.