Effects of Giant Planet Migration on Terrestrial Planet Composition

The Compositional Diversity of Extrasolar Terrestrial Planets: II. Migration Simulations
http://arxiv.org/abs/1209.5125

Quote :

Prior work has found that a variety of terrestrial planetary compositions are expected to occur within known extrasolar planetary systems. However, such studies ignored the effects of giant planet migration, which is thought to be very common in extra-solar systems. Here we present calculations of the compositions of terrestrial planets that formed in dynamical simulations incorporating varying degrees of giant planet migration. We used chemical equilibrium models of the solid material present in the disks of five known planetary host stars: the Sun, GJ 777, HD4203, HD19994 and HD213240. Giant planet migration has a strong effect on the compositions of simulated terrestrial planets as the migration results large-scale mixing between terrestrial planet building blocks that condensed at a range of temperatures. This mixing acts to 1) increase the typical abundance of Mg-rich silicates in the terrestrial planets feeding zones and thus increase the frequency of planets with Earth-like compositions compared with simulations with static giant planet orbits; and 2) drastically increase the efficiency of the delivery of hydrous phases (water and serpentine) to terrestrial planets and thus produce water worlds and/or wet Earths. Our results demonstrate that although a wide variety of terrestrial planet compositions can still be produced, planets with Earth-like compositions should be common within extrasolar planetary systems.

Interesting that migration aids the production of planets with Earthlike compositions, particularly if you consider the possibility of the "Grand Tack" scenario for Jupiter and Saturn. Also seems to tie in to the observations of disrupted rocky objects (asteroids/dwarf planets?) around white dwarfs.