  Super-Earths and mini-Neptunes exhibit great diversity in their compositional
and orbital properties. Their bulk densities span a large range, from those
dense enough to be purely rocky to those needing a substantial contribution
from volatiles to their volumes. Their orbital configurations range from
compact, circular multi-transiting systems like Kepler-11 to systems like our
Solar System's terrestrial planets with wider spacings and modest but
significant eccentricities and mutual inclinations. Here we investigate whether
a continuum of formation conditions resulting from variation in the amount of
solids available in the inner disk can account for the diversity of orbital and
compositional properties observed for super Earths, including the apparent
dichotomy between single transiting and multiple transiting system. We simulate
in situ formation of super-Earths via giant impacts and compare to the observed
Kepler sample. We find that intrinsic variations among disks in the amount of
solids available for in situ formation can account for the orbital and
compositional diversity observed among Kepler's transiting planets. Our
simulations can account for the planets' distributions of orbital period
ratios, transit duration ratios, and transit multiplicity; higher
eccentricities for single than multi transiting planets; smaller eccentricities
for larger planets; scatter in the mass-radius relation, including lower
densities for planets with masses measured with TTVs than RVs; and similarity
in planets' sizes and spacings within each system. Our findings support the
theory that variation among super-Earth and mini-Neptune properties is
primarily locked in by different in situ formation conditions, rather than
arising stochastically through subsequent evolution.
