  We use an established discrete element method (DEM) Reynolds-averaged
Navier--Stokes (RANS)-based numerical model to simulate non-suspended sediment
transport across conditions encompassing almost seven orders of magnitude in
the particle--fluid density ratio $s$, ranging from subaqueous transport
($s=2.65$) to aeolian transport in the highly rarefied atmosphere of Pluto
($s=10^7$), whereas previous DEM-based sediment transport studies did not
exceed terrestrial aeolian conditions ($s\approx2000$). Guided by these
simulations and by experiments, we semi-empirically derive simple scaling laws
for the cessation threshold and rate of equilibrium aeolian transport, both
exhibiting a rather unusual $s^{1/3}$-dependence. They constitute a simple
means to make predictions of aeolian processes across a large range of
planetary conditions. The derivation consists of a first-principle-based proof
of the statement that, under relatively mild assumptions, the cessation
threshold physics is controlled by only one dimensionless control parameter,
rather than two expected from dimensional analysis. Crucially, unlike existing
models, this proof does not resort to coarse-graining the particle phase of the
aeolian transport layer above the bed surface. From the pool of existing
models, only that by P\"ahtz et al. (\textit{J. Geophys. Res. Earth.
Surf.}~126, e2020JF005859, 2021) is somewhat consistent with the combined
numerical and experimental data. It captures the scaling of the cessation
threshold and the $s^{1/3}$-dependence of the transport rate, but fails to
capture the latter's superimposed grain size dependence. This hints at a lack
of understanding of the transport rate physics and calls for future studies on
this issue.
