Formation of calcium sulfate through the aggregation of sub-3 nanometre primary species

摘要: The formation pathways of gypsum remain uncertain. Here, using truly in situ and fast time-resolved small-angle X-ray scattering, we quantify the four-stage solution-based nucleation growth (CaSO4·2H2O), an important mineral phase on Earth Mars. reaction starts through well-defined, primary species <3 nm length (stage I), followed stage II by their arrangement into domains. variations volume fractions electron densities suggest that these forming contain Ca-SO4-cores self-assemble III large aggregates. Within aggregates well-defined start to grow IV), fully crystalize a structural rearrangement. Our results allow for quantitative understanding how natural calcium sulfate deposits may form terrestrially unstable phase-like bassanite can persist at low-water activities currently dominating surface