  Building the terrestrial planets has been a challenge for planet formation
models. In particular, classical theories have been unable to reproduce the
small mass of Mars and instead predict that a planet near 1.5 AU should roughly
be the same mass as the Earth. Recently, a new model called Viscous Stirred
Pebble Accretion (VSPA) has been developed that can explain the formation of
the gas giants. This model envisions that the cores of the giant planets formed
from 100 to 1000 km bodies that directly accreted a population of pebbles ---
sub-meter sized objects that slowly grew in the protoplanetary disk. Here we
apply this model to the terrestrial planet region and find that it can
reproduce the basic structure of the inner Solar System, including a small Mars
and a low-mass asteroid belt. Our models show that for an initial population of
planetesimals with sizes similar to those of the main belt asteroids, VSPA
becomes inefficient beyond $\sim\!$1.5 AU. As a result, Mars's growth is
stunted and nothing large in the asteroid belt can accumulate.
