Panels a–d: azimuthally-averaged dust grain densities for 2 and 100 µm EKB and OCC grains, as marked. The projection of Pluto’s orbit in the r−z plane is overlaid as the solid black curve and its position in 2015 as the black dot, where [r, z] = [0, 0] is the position of the Sun. The position of Triton and Neptune is denoted as the open circle. Panels e and f: the EKB and OCC dust grain velocity distributions at Pluto as a function of grain mass. Panels g and h: the EKB and OCC dust grain velocity distributions at Triton as a function of grain mass. Each mass bin is individually normalized.