Periodic microstructure in Saturn's rings A and B

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 λ gr ≈ 100–250 meters and orientation ϕ gr ≈ 0. In particular, two regions in Ring A of radial extent 123.05–123.4 × 10 3 km and 123.6–124.6 × 10 3 km yield average estimates of gr = 163 ± 6 meters and gr = 217 ± 8 meters, respectively. Three regions in Ring B of radial extent 92.1–92.6 × 10 3 , 99.0–104.5 × 10 3 km, and 110.0–115.0 × 10 3 yield average estimates of gr = 115 −15 +20 , 146 ± 14, and 250 −75 +150 meters, respectively. In all regions, the structure appears to be azimuthally symmetric with −3° ≤ ϕ gr ≤ 3°.