Spin deposited directly on the planet’s surface as a function of Stokes number and planet mass for a planet at 10 au. Panel a shows the spin in the presence of an atmosphere and panel b when there is no atmosphere. To give an impression of how these spin values relate to those measured in the Solar System, the spin value of Neptune (ω_z ≈ 0.16ω_crit) is indicated in panels a and b using a black contour. In panel c the absolute reduction (blue) or enhancement (red) of the spin due to the atmosphere is plotted. In this panel, the absolute difference has been multiplied by the sign of the spin without an atmosphere so that a reduction brings the spin closer to zero, while an enhancement moves the spin farther from zero, irrespective of whether the spin is prograde or retrograde. Finally, panel d shows the percentage difference between the two models. The black contour in this plot indicates the region in which 100% of the spin is absorbed by the atmosphere. The colour scale in panel d has been cut off at −100% and +500%. Data points outside this range, which are artefacts due to the spin without an atmosphere becoming zero, have been masked (grey).