Determine the physical mechanism suppressing ejections outside the rocky southern terrain

Determine which combinations of material properties or physical processes in comet 67P/Churyumov–Gerasimenko naturally suppress dust ejections in regions outside the rocky southern terrain while reproducing the observed water production, non-gravitational accelerations, and torques.

Background

The two-layer thermophysical model reproduces the observations most successfully when dust-crust ejections are artificially restricted to the rocky southern terrain. The authors tested variations in aggregate size, dust-to-ice ratio, tensile-strength laws, and related parameters, but did not identify a physically motivated combination that naturally generated the weaker activity required in the other geomorphological regions.

The unresolved issue is whether the reduced activity outside the rocky south results from greater local tensile strength, lower water content, fallback burial, thermal inertia, or another form of regional heterogeneity. Resolving this issue is important for connecting the modelled activity to the observed geological and seasonal differences across the nucleus.