The Compositional Diversity of Extrasolar Terrestrial Planets: II. Migration Simulations

TL;DR

This study models how giant planet migration influences the composition of terrestrial exoplanets, revealing that such migration promotes Earth-like compositions and water delivery, thus making water-rich Earth analogs common.

Contribution

It introduces dynamical simulations incorporating giant planet migration to predict terrestrial planet compositions, highlighting the impact of migration on planetary diversity.

Findings

Migration increases Mg-rich silicates in planets.

Migration enhances water and serpentine delivery.

Earth-like planets are likely common in extrasolar systems.

Abstract

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.