Left: Comparison of the different predicted bulk density profiles at 70° latitude; constant regolith properties (solid line), variation in deep layer density (dashed line), and transition width (dash-dotted line). Illustrated together with the bulk density inferred from ChaSTE (cross) at ∼−69° latitude (Mathew et al. 2025). Right: Bulk density profiles resulting from the predicted poleward decrease in deep layer density in steps of 10° latitude and a start at 40° latitude.