In a recent pair of papers published in the November, 2004 Astronomical Journal, Department researcher Bill Ward and colleague Doug Hamilton (U. Maryland) have made a major advance in understanding the origin of Saturn's spin axis.
The tilt of Saturn's spin axis to its orbit plane is 26.7 degrees, while that of Jupiter is only 3.1 degrees. Ward and Hamilton offer an explanation for this puzzling difference owing to gravitational perturbations of Saturn by the planet Neptune. A similarity between the precession period of Saturn's spin axis and the 1.87x10^6 (1,870,000) year precession period of Neptune's slightly inclined orbit plane implicates a resonant interaction between these planets as responsible for tilting Saturn from an initially more upright state. Ward and Hamilton make a case that Saturn was captured into this resonance during the erosion of the Kuiper belt, which decreased the rate of regression of Neptune's orbit plane. Penetrating the resonance pumped up Saturn's obliquity to its current value. The spin axis may also be librating in the resonance with an amplitude of 31 degrees, and we discuss possible causes of this and the implied constraint on the Saturn moment of inertia. Matching the current pole position to the predicted outcome may place new constraints on early solar system processes.
Ward, W. R. & D. P. Hamilton, Tilting Saturn. I. Analytic Model, Astron. J. 128, 2501-2509.