  Super Earths are the largest population of exoplanets and are seen to exhibit
a rich diversity of compositions as inferred through their mean densities. Here
we present a model that combines equilibrium chemistry in evolving disks with
core accretion that tracks materials accreted onto planets during their
formation. In doing so, we aim to explain why super Earths form so frequently
and how they acquire such a diverse range of compositions. A key feature of our
model is disk inhomogeneities, or planet traps, that act as barriers to rapid
type-I migration. The traps we include are the dead zone, which can be caused
by either cosmic ray or X-ray ionization, the ice line, and the heat
transition. We find that in disks with sufficiently long lifetimes ($\gtrsim$ 4
Myr), all traps produce Jovian planets. In these disks, planet formation in the
heat transition and X-ray dead zone produces hot Jupiters while the ice line
and cosmic ray dead zones produce Jupiters at roughly 1 AU. Super Earth
formation takes place within short-lived disks ($\lesssim$ 2 Myr), whereby the
disks are photoevaporated while planets are in a slow phase of gas accretion.
We find that super Earth compositions range from dry and rocky ($<$ 6 % ice by
mass) to those with substantial water contents ($>$ 30 % ice by mass). The
traps play a crucial role in our results, as they dictate where in the disk
particular planets can accrete from, and what compositions they are able to
acquire.

Earth and Planetary Astrophysics