Apsidal precession of migrating particles as the cause for the double-crescent density pattern generated by Mars (no other planets present, β = 0.005). The figure shows the orbit of an exemplary particle before and after traversing the orbit of Mars. As the particle’s perihelion drops inside the orbit of Mars under PR drag, it starts to experience a negative apsidal drift that is maintained until it revolves entirely within the orbit of Mars. The apsidal drift is causing one side of the trajectory to fall off faster than the other, apparent in the varying gap width between the two orbits. All particles experiencing a drift with preferred final apse line orientation with respect to that of Mars, thus generate a mirrored depletion–enhancement pattern.