  Modern terrestrial planet formation models are highly successful at
consistently generating planets with masses and orbits analogous to those of
Earth and Venus. In stark contrast to classic theoretical predictions and
inferred demographics of multi-planet systems of rocky exoplanets, the mass
(>10) and orbital period (>2) ratios between Venus and Earth and the
neighboring Mercury and Mars are not common outcomes in numerically generated
systems. While viable solutions to the small-Mars problem are abundant in the
literature, Mercury's peculiar origin remains rather mysterious. In this paper,
we investigate the possibility that Mercury formed in a mass-depleted, inner
region of the terrestrial disk (a < 0.5 au). This regime is often neglected in
terrestrial planet formation models because of the high computational cost of
resolving hundreds of short-period objects over ~100 Myr timescales. By testing
multiple disk profiles and mass distributions, we identify several promising
sets of initial conditions that lead to remarkably successful analog systems.
In particular, our most successful simulations consider moderate total masses
of Mercury-forming material (0.1-0.25 Earth masses). While larger initial
masses tend to yield disproportionate Mercury analogs, smaller values often
inhibit the planets' formation as the entire region of material is easily
accreted by Venus. Additionally, we find that shallow surface density profiles
and larger inventories of small planetesimals moderately improve the likelihood
of adequately reproducing Mercury.
