Modeling of ice pinnacle formation on Callisto

Abstract

Callisto's pinnacle terrain has been interpreted to form through sublimation weathering of bedrock and subsequent deposition of the sublimated ice in local cold traps on peaks and crater rims. To investigate how these processes are affected by environmental parameters, including solar illumination and the composition and concentration of ices in the crust, we employ the MARSSIM landform evolution model and advance its treatment of the physics that underlies the relevant processes. Both ice sublimation and deposition are controlled by surface temperature, which we calculate based on energy contributions from both insolation and thermal reradiation from the surrounding landscape. We perform 4.5 Gyr duration simulations whereby we separately consider and model CO 2 and H 2 O as the crustal ice species. We find that sublimating a crustal content of 10% CO 2 ice (a reasonable but arbitrarily selected value) yields present-day landform degradation and regolith coverage that is comparable to what is observed on Callisto. In our H 2 O ice simulations we reproduce the essential features of pinnacle ice distribution at both the equator and midlatitudes. Our present nominal crustal H 2 O ice content is 33%, which produces a maximum pinnacle ice thickness of 64 m. Pinnacle height is likely limited by collapse or mass wasting of the ice once it reaches a certain thickness.

Topographic Constraints on the Evolution and Connectivity of Titan's Lacustrine Basins

“…This is analogous to the formation of pingos. Similarly, erosion by sublimation followed by reprecipitation of volatiles can generate pits with raised rims, a process analogous to the formation of penitentes on Callisto (White et al, ). Thermodynamically, sublimation erosion is difficult given the lack of significant temperature gradients (Cottini et al, ) and the scarcity of known volatile species on Titan's surface today.…”

Color, composition, and thermal environment of Kuiper Belt object (486958) Arrokoth

“…Solutions to Eq. S3 are developed in the time-asymptotic limit whereby we impose the condition that the conductive flux goes to zero sufficiently deep underneath the surface (39). This amounts to representing the solution for the temperature for z < 0 as a truncated sum in powers of seasonal frequency, i.e.,…”

Geological mapping of Sputnik Planitia on Pluto

“…also cause the residual tholins to build up as a layer of lag on the surface in a manner comparable to how the lag in Callisto"s dark, inter-crater plains is interpreted to form (e.g. Moore et al, 1999;White et al, 2016).…”

“…The low albedo of the tholins would initially enhance heating, and therefore promote further sublimation and pit growth rates, in the N 2 ice that underlies them, but eventual accumulation of a certain thickness of tholins on their floors would presumably act to suppress further sublimation (e.g. Moore et al, 1999;White et al, 2016). This scenario is not especially likely for where the Deeply Pitted Plains exist between cells of the Bright, Cellular Plains ("1" label in Fig.…”