  While it is accepted that the eccentricity of Mercury (0.206) favours
entrapment into the 3:2 spin-orbit resonance, open is the question how and when
the capture took place. A recent work by Makarov (2012) has demonstrated that
trapping into this resonance is certain if the eccentricity is larger than 0.2,
provided that we use a realistic tidal model, the one which is based on the
Darwin-Kaula expansion of the tidal torque. The physics-based tidal model
changes dramatically the statistics of the possible final spin states. First,
we discover that after only one encounter with the spin-orbit 3:2 resonance
this resonance becomes the most probable end-state. Second, if a capture into
this (or any other) resonance takes place, the capture becomes final, several
crossings of the same state being forbidden by our model. Third, within our
model the trapping of Mercury happens much faster than previously believed: for
most histories, 10 - 20 Myr are sufficient. Fourth, even a weak laminar
friction between the solid mantle and a molten core would most likely result in
a capture in the 2:1 or even higher resonance. So the principal novelty of our
paper is that the 3:2 end-state is more ancient than the same end-state
obtained when the constant time lag model is employed. The swift capture
justifies our treatment of Mercury as a homogeneous, unstratified body whose
liquid core had not yet formed by the time of trapping. We also provide a
critical analysis of the hypothesis by Wieczorek et al. (2012) that the early
Mercury might had been retrograde, whereafter it synchronised its spin and then
accelerated it to the 3:2 resonance. Accurate processing of the available data
on cratering does not support that hypothesis, while the employment of a
realistic rheology invalidates a key element of the hypothesis, an intermediate
pseudosynchronous state needed to spin-up to the 3:2 resonance.
