An experimental approach to production of peptide-like compounds in the early terrestrial planets

A mixture of six DL-amino acids in prebiotic proportions were immersed in heavy mineral oil, warmed up to 240°C and exposed to the action of spark discharges on a mixture of H2O and CO2 gases. Water soluble products were analyzed by Fourier transformed infrared spectroscopy (FTIR) showing yields of peptide-like compounds characterized by amidine linkages and other molecules consisting of aromatic and non-aromatic alcohols and nitrogenous aromatics. Non-soluble products analyzed by scanning electron microscopy (SEM) revealed the presence of a material comparable to tholins whereas the products soluble in water showed the presence of an amphiphilic component. The recovered amounts and the FTIR spectra corresponding to heavy mineral oil exposed to simulated experimental conditions including UVC-radiations, clearly show no difference relative to initial sample indicating that the decomposition rate of these molecules should be very slow at the time. Therefore, we consider plausible that alkane environments ⩾n-C18 occurring on the early terrestrial planets could offer several advantages for the synthesis and survival of nitrogenous molecules, particularly towards the end or after the age of the large impacts, such as protection against oxidizing atmospheres, high temperatures generated by greenhouse effects or shock waves and protection against decomposition effects caused by high UVC-radiations, corona discharges and lightning. Currently, these facts could be happening in other regions of our solar system and in extrasolar planets allowing the formation and accumulation of complex nitrogenous molecules.