The fate of aerosols on the surface of Titan.
Résumé
A laboratory study based on the chemical transformation that Titan's aerosol analogues suffer when placed under putative surface conditions of the satellite was performed. In order to understand the role that aqueous ammonia may play on the chemical transformation of atmospheric aerosols once they reach the surface, we synthesized laboratory analogues of Titan's aerosols from an N2 : CH4 (98 : 2) mixture irradiated at low temperatures under a continuous flow regime by a cold plasma discharge of 180 W. The analogues were recovered, partitioned in several 10.0 mg samples and placed inside different ammonia concentrations during 10 weeks at temperatures as low as those reported for Titan's surface. After a derivatization process performed to the aerosols' refractory phase with MTBSTFA in DMF, the products were identified and quantified using a GC-MS system. We found derived residues related to amino acids as well as urea. The simplest amino acids aminoethanoic acid (glycine) and 2-aminopropanoic acid (alanine) as well as diaminomethanal (urea), are found regardless of the ammonia concentration and temperature value to which the aerosol analogues were exposed. Our results have important astrobiological implications to Titan's environment particularly if the existence of the suggested subsurface water-ammonia mixture and its deposition on the satellite's surface is validated.