Periodic microstructure in Saturn's rings A and B

Abstract

Diffraction of coherent radio waves transmitted by the Cassini spacecraft at 0.94- and 3.6-cm wavelengths indicates the presence of fine-scale structure in Saturn's rings A and B, characterized by a periodic radial variation in optical depth. Interpretation of the observed spectral signature in terms of a simple diffraction grating model yields estimates of the structural period λgr ≈ 100-250 meters and orientation φgr ≈ 0. In particular, two regions in Ring A of radial extent 123.05-123.4 × 103 km and 123.6-124.6 × 103 km yield average estimates of ∇λgr = 163 ± 6 meters and ∇λgr = 217 ± 8 meters, respectively. Three regions in Ring B of radial extent 92.1-92.6 × 103, 99.0-104.5 × 103 km, and 110.0-115.0 × 103 yield average estimates of ∇λgr = 115-15+20, 146 ± 14, and 250-75+150 meters, respectively. In all regions, the structure appears to be azimuthally symmetric with -3° ≤ φgr ≤ 3°. Copyright 2007 by the American Geophysical Union.