Shock-induced pyrolysis of amino acids at ultra high pressures ranged from 3.2 to 35.3 GPa

Survivability of amino acids at impact shock is an important factor to estimate the quantity of amino acids delivered by extraterrestrial bodies to the early Earth. In the study, we conducted shock recovery experiments of amino acids to understand the specific behaviors of amino acids by shock-induced pyrolysis during extraterrestrial impacts. Four amino acids (glycine, alanine, α-aminobutyric acid, and α-aminoisobutyric acid) that are abundant in meteorites were selected and mixed with mineral (serpentinite) powder to imitate asteroidal impacts. The shock pressure range achieved in the study was 3.2–35.3 GPa and the corresponding shock temperature range was calculated to be 420–830 K. The results show that survivability of the four amino acids declines steeply to 5–8% at 18.4 GPa and most of amino acids were decomposed at 35.3 GPa. These results mean that shock-induced pyrolysis of amino acids proceeds within an extremely short period of time (0.6–0.8 μs) and has a reaction mechanism independent on chemical structures of amino acids. To compare with normal pyrolysis of amino acids at the atmospheric pressure, shock-induced pyrolysis of them is more rapid and dynamic reaction. The specific conditions of shock-induced pyrolysis; ultra high pressure and some special effects at a shock front (acceleration of particles and non-equilibrium phenomena) may be responsible for the specificities of the reactions. Our results provide new data for more realistic examination of extraterrestrial delivery of amino acids to the early Earth.