Mass and interior of Enceladus from Cassini data analysis

Gravity results are available from radio Doppler data acquired by the Deep Space Network during the encounter of the Cassini spacecraft with Enceladus in February 2005. We report the mass of Enceladus to be (1.0798±0.0016)×1020 kg(1.0798±0.0016)×1020 kg, which implies a density of 1608.9±4 kgm−3. For a core made of hydrated silicates with a density of 2500 kg m−3 the core radius is ∼190 km∼190 km and the quadrupole moment C22∼1.4×10−3C22∼1.4×10−3. If Enceladus is in hydrostatic equilibrium, the larger than previously anticipated density implies that the recently proposed secondary spin–orbit resonance cannot be present. Therefore, the source of endogenic activity of Enceladus remains unexplained.