Saturn's satellites: Nuar-infrared spectrophotometry (0.6–2.5 μm) of the leading and trailing sides and compositional implications

Arecibo radar observations of Rhea, Dione, Tethys, and Enceladus

“…review by Clark et al, 1986). The Saturn satellites have optical albedos similar to the jovian satellites as well as similar water ice band depths in the infrared (Clark et al, 1984), but follow a different trendline in Fig. 2.…”

“…The Cassini mission has recently performed close flybys of these moons, confirming that varying degrees of geologic activity (Wagner et al, 2006) were sustained for an extended period of time on these small objects after their formation, and continuing to the present on Enceladus (Porco et al, 2006). The surfaces of each are known to be fairly clean water ice (Clark et al, 1984) with high optical albedos, and with each exhibiting color and brightness variations indicating heterogeneous coverage of non-ice impurities and surface microstructure. Large scale variations take the form of leading versus trailing hemisphere asymmetries (Buratti and Veverka, 1984), which for these synchronously rotating bodies may be related to interactions with Saturn's magnetospheric plasma and/or the diffuse E-ring in both of which these moons are embedded (Verbiscer et al, 2007), or focusing of micrometeorite impacts due to their orbital motion (cf.…”

Magnetospheric ion bombardment profiles of satellites: Europa and Dione

“…Leading/trailing differences in the IR absorption signature of H20 observed by Clark et al (1984) have been attributed to differences in the bombardment rates. The differences in plasma bombardment rates result in different sputter erosion rates (e.g., Johnson et al 1984) so that the average grain size on the two hemispheres is different.…”

“…A UV band observed on the trailing hemisphere of Europa was identified by Lane et al (1981) as an SO band produced by implanted sulfur ions originating from the Io plasma torus. Clark et al (1983) attributed spatial differences in the water ice IR band depth as being due to plasma bombardment (see also Clark et al 1984Clark et al , 1986.…”

“…The spatial distribution of ejected neutrals is also dependent on the pattern of ion bombardment of satellite surfaces (Johnson et al 1978b). As recent measurements of IR band depths by Clark et al (1984) indicate that this bombardment is not is•tropic, a detailed study of ion bombardment profiles of satellites is needed to correctly describe the heavy ion source distribution at Saturn. in this paper we will discuss a general model of the magnet•spheric ion bombard-ment which can be applied to any satellite subject to such a bombardment.…”