Fachbereich 14 - Geowissenschaften
Institut für Planetologie
Planetenphysik

Differentiation of Callisto

The recently measured dimensionless moment of inertia (MoI) factor for Callisto of 0.3549 poses a problem: Its value cannot be explained by a model in which Callisto is completely differentiated into an ice shell above a rock shell and an iron core such as its neighboring satellite Ganymede nor can it be explained by a model of a homogeneous, undifferentiated ice-rock satellite. We show that Callisto may be incompletely differentiated into an about 100 km thick outer ice-rock shell in which the volumetric rock concentration is close to the primordial one, an ice mantle mostly depleted of rock, and an about 1800 km rock-ice core in which the rock concentration is close to the close-packing limit. We show that if Callisto accreted from a mix of metal bearing rock and ice and if the average size of the rocks was of the order of meters to tens of meters, then Callisto may have experienced a gradual, but still incomplete unmixing of the two components.

Drittmittelgeber:

Deutsche Forschungsgemeinschaft

Beteiligte Wissenschaftler:

Dr. Klaus Nagel, Dr. Doris Breuer, Dr. Tilman Spohn

Veröffentlichungen:

Breuer D., 2002: Modelling the interiors of Earth-like planets and moons. ESLAB36 Symposium: Earth-like planets and moons, June 3-8, ESTEC, Noordwijk, The Netherlands.

Breuer D., T. Spohn, and K. Nagel, 2002: A model for the evolution and incomplete differentiation of Callisto. Euroconference: Jupiter after Galileo and Cassini, June 17-21, Lisbon, Portugal.

Nagel, K., D. Breuer, and T. Spohn, 2003: A model for the interior structure, evolution, and differentiation of Callisto, submitted to Icarus