This MR abstract of a paper by Henry McKean from 1960 looks relevant: << MR0133869 (24 #A3693) 60.62 McKean, H. P., Jr. Brownian motions on the 3-dimensional rotation group. Mem. Coll. Sci. Univ. Kyoto Ser. A Math. 33 1960/1961 25–38 . . . . . . An application describes the motion of a sphere rolling without slipping on a plane while its center performs Brownian motion [see also C. D. Gorman, Trans. Amer. Math. Soc. 94 (1960), 103–117; MR0115218 (22 #6020)]. _____________________________________________________________________ "It don't mean a thing if it ain't got that certain je ne sais quoi." --Peter Schickele