Isosurfaces of the iron distribution for models N16.3 (upper left panel), B18.3 (lower left), and S19.8 (lower right) at day 730. The semi-transparent isosurfaces correspond to a value of the iron density which is at 10% of the peak density for each model (maximum iron density is 4.9 × 10⁻¹⁶ g cm⁻³ for N16.3, 6.0 × 10⁻¹⁶ g cm⁻³ for B18.3, and 1.1 × 10⁻¹⁵ g cm⁻³ for S19.8). The colors give the velocity along the LoS in units of 1000 km s⁻¹ on the isosurface; the color coding is defined at the bottom of each panel. The yardstick indicating the length scale is on the left. The upper right panel shows the line profiles of [Fe II] 26 μm and 18 μm of SN 1987A observed during the first 2 years of evolution (symbols; Haas et al. 1990) and synthesized from models N16.3, B18.3, and S19.8 at day 730 (solid lines). See online Movie 1 for an animation of these data; a navigable 3D graphic of the iron distribution for the three models is available at https://skfb.ly/6P7sH.