The generation of organic compounds relevant to the origin of living beings is easily achieved if reducing conditions exist in the environment; however, proposed models of primitive atmospheres do not favour these conditions. This work considers the quantity and possible size of the cosmic bodies that could have impacted the Earth between 4.2 and 3.8 Ga. Different atmospheres (with gases such as CO2, CO, N2, CH4) were experimentally irradiated by an Nd-YAG laser (used to simulate the energy of a shock wave produced by the interaction of a cosmic body with the atmosphere). Although the main products are short-chain, saturated and unsaturated hydrocarbons, hydrogen cyanide (HCN) is the most abundant in some atmospheres. HCN is an important precursor of the organic molecules relevant to chemical evolution. According to our calculations, between 1023 and 1025 g of HCN could have been produced by the energy released to the atmosphere from the entry of cosmic objects between 4.2 and 3.8 Ga. Therefore, this shock wave energy could play an important role in the processes of chemical evolution.
