Abstract:
Emergence of life's building blocks is an essential step in any models of the origins of life. However, it remains unclear how these molecules formed on the early Earth covered by N2- and CO2-dominated atmosphere. Lunar crater records suggest that meteorite impacts had been far more common at that age. Most meteorites collected on the Earth contain metallic iron, which works as a reductant in N2-CO2 atmosphere. Thus, meteorite impacts have potential to create organic compounds. We have investigated such impact-induced reactions using a single stage propellant gun and a gas-flow line reactor. Shock-induced reaction between C (amorphous), Fe, Ni, H2O, and N2 provided aliphatic amines and carboxylic acids; glycine was formed as well when NH3 was added to the starting material. In the latest series of experiments, we replaced carbon source from amorphous carbon to bicarbonate simulating a component in an ancient ocean, and then we found the formation of two kinds of nucleobases and nine kinds of proteinogenic amino acids. The formation of organics by impacts might provide an insight into the origins of life's building blocks on the prebiotic Earth.