Aging and degradation of urea nitrate below the melting point, at 100 degrees C, was studied by using thermal analysis and spectroscopic methods including IR, Raman, (1)H and (13)C NMR techniques. It was found that urea nitrate was completely degraded after 72h at 100 degrees C into a mixture of solids (69%) and released gaseous species (31%). The degradation mechanism below the melting point was clearly identified. The remaining solid mixture was composed of ammonium nitrate, urea and biuret while unreacted residual nitric and isocyanic acids as well as traces of ammonia were released as gaseous species at 100 degrees C. The thermal stability of urea nitrate, under extreme storage conditions (50 degrees C), was also examined by isothermal nano-calorimetry. (C) 2011 Elsevier B.V. All rights reserved.