Anderson J D, Schubert G, Jacobson R A, Lau E L, Moore W B, Sjogren W L
Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California 91109-8099, USA.
Science. 1998 Jun 5;280(5369):1573-6. doi: 10.1126/science.280.5369.1573.
Radio Doppler data from a single encounter (C3) of the Galileo spacecraft with Callisto, the outermost Galilean moon of Jupiter, indicated that Callisto was probably undifferentiated. Now, similar data from a second encounter (C9) corroborate this conclusion, but more accurate data from a third encounter (C10) indicate that the rock and ice within Callisto have partially, but not completely, separated. Callisto may be differentiated into a rock-metal core less than 25 percent of Callisto's radius, an outer layer of clean ice less than 350 km thick, and a middle layer of mixed rock and ice. Models in which ice and rock are mixed all the way to the center of Callisto are also consistent with the data.
伽利略号航天器与木星最外层的伽利略卫星木卫四单次交会（C3）所获取的射电多普勒数据表明，木卫四可能未发生分化。如今，第二次交会（C9）得到的类似数据证实了这一结论，但第三次交会（C10）获取的更精确数据显示，木卫四内部的岩石和冰已经部分（但并非完全）分离。木卫四可能分化为一个半径小于木卫四半径25%的岩金属内核、一层厚度小于350千米的纯净冰外层，以及一层岩石与冰混合的中间层。冰和岩石一直混合到木卫四中心的模型也与这些数据相符。
