Identification of Possible Heat Sources for the Thermal Output of Enceladus

We have calculated the amount of radioactive heat production (RHP) that could possibly prevent the postulated underground ocean of Enceladus from freezing. An internal heat source is necessary to justify the observed heat output from Enceladus and to allow the tidal dissipation heating models to work. Also based on the terrestrial evidence, we have assumed that the most common radiogenic element that can produce such internal heat is U-238. Our results show that a minimum amount in the range 38.10-76.59 ppm of U-238, averaged over the whole mass of Enceladus, is necessary to obtain the required RHP. The range of values increases to 63.60-127.70 ppm if we consider only the mass of the rocky portion and 2890-5775 ppm if we consider the mass of the rock + ice portion of Enceladus just below the southern polar area. Even in the latter case, the concentration of uranium is still well below the amount found in high-grade ore on Earth.