Icy Satellites of Saturn: Impact Cratering and Age Determination

Ion Composition in Titan's Exosphere via the Cassini Plasma Spectrometer

“…Shape and gravity measurements indicate densities consistent with water ice and varying silicate content [Matson et al, 2009], and while there is evidence for resurfacing in the past, craters and fractures suggest little present-day geologic activity on all but Enceladus [Dones et al, 2009]. The variation in silicate content among the cores of these inner moons, which ranges from 6% (Tethys) to 57% (Enceladus), has been attributed to a compact, massive proto-disk containing silicates and ice.…”

Radiation Effects on Airless Bodies in Space: Radiolysis, Sputtering, and Sintering in Regoliths

“…The small crater populations on Saturnian satellites suggest size frequency distributions such as those given by Eq. 2.18 where b ∼ 0.9−1.2 [Dones et al, 2009]. Likewise, taking either the cumulative number density slopes or the differential slopes gives regolith overturn timescales that are all negative Kirchoff and Schenk [2009].…”

“…The icy Saturnian satellite surfaces are characterized by population II type crater distributions, mean a high density of small craters, and general hemispheric uniformity of craters, thus suggesting the bulk of the impacting material is planetocentric in orbit [Dones et al, 2009]. However, in order to account for the larger craters present, heliocentric comets should be considered as well.…”

“…Using the cometary chronology limits discussed above, where for case A the majority of the small craters are produced by planetocentric impactors, the cratering time scales, τ rs , are given in Tab. A-2 for D > 20km [Dones et al, 2009]. Using…”

“…2.23 to estimate the overturn timescale by assuming that h eq >> h and that c eq is of order unity [Phillips and Chyba, 2001;Melosh, 2011]. These are likely good approximations at small depths (<<km) and since the surface of Mimas appears to be in equilibrium with only a small range of ∼km crater sizes visible [Dones et al, 2009].…”