The non enzymatic elongation of RNA oligomers by activated RNA dimers and other oligomers in eutectic ice phases is investigated. Eutectic salt-ice mixtures contain channels of liquid aqueous solutions with a high molecule concentration or brines, which form an environment conductive to spontaneous, metal catalyzed condensation reactions (s. micrograph, right). With a new, non-radioactive ex-perimental essay we are selectively monitoring the 5'-3' and 5'-2' elongation of 5'-fluorescence labeled RNA oligomers. At - 18.5 °C the polymerization reaction and its selectivity is expected to be much higher than at room temperature. In the case of a mixed dimer or oligomer experiment this might lead to a particular sequence distribution. The concurrence between polymerization and degradation seen in the previous work shall be further investigated, focusing on possible sequences stabilizing and increasing (“cooperative sequences”) or degrading (“parasitic sequences”) the RNA population. These eutectic phases in water-ice are plausible prebiotic micro-environments that should help to overcome the dilution problem in origin of life scenarios. They might have supported the production of libraries/populations of longer RNA chains rising the potential to produce (auto-)catalytic active molecular species (e.g. ribozymes).