Differentiation of silicates from H2O ice in an icy body induced by ripening

Abstract

One of the probable scenarios of differentiation between silicate-ice in an icy object is the settling of a silicate particle in water after the melting of the object. In order for settling to proceed or occur, the size of the particle should be sufficiently large such that the settling velocity of the particle exceeds the background flow velocity induced by thermal convection. The sizes of the particles change because of dissolution and precipitation. This process is called ripening. In this study, the critical particle sizes required for settling, and the timescales for the growth of the particles to these sizes through ripening, are analytically derived. It is observed that settling is possible if the silicate particles coagulate with each other to form a network in water. If the particles do not coagulate, the probability of the occurrence of settling is low, because the time duration required for the particle growth to the critical size is large. The coagulation of silicate particles strongly depends on the pH of the water.

Ongoing hydrothermal activities within Enceladus

“…The ratio of S 0 (T 0 )/S 0 (T) is calculated as 1.67 for T 5 0uC (ref. 21). Thus, the timescale for a 2-nm-sized nanosilica particle to grow to an 8-nm-sized particle at 0 uC in pure water is estimated as ,20 years.…”

“…Timescale of growth of nanosilica in Enceladus' ocean. We estimated this on the basis of the equation shown in the previous study 21 . The primary size of nanosilica formed from alkaline aqueous solution is a few nanometres in radius 12,[14][15][16][17] .…”

Science Drivers for the Future Exploration of Ceres: From Solar System Evolution to Ocean World Science

“…Pros and cons for that model are summarized in Castillo-Rogez & Bland (2021). The main open question is whether fine rock particles would remain in suspension for billions of years and avoid processes such as hydrolysis (Sirono 2013) and flocculation (e.g., Kranck 1973). In that model, the temperatures in the rocky mantle are too cold for the onset of hydrated rock thermal metamorphism.…”