Editor’s note: Astrobites is a graduate-student-run organization that digests astrophysical literature for undergraduate students. As part of the partnership between the AAS and astrobites, we occasionally repost astrobites content here at AAS Nova. We hope you enjoy this post from astrobites; the original can be viewed at astrobites.org.
Title: The Solar Wind Prevents Reaccretion of Debris after Mercury’s Giant Impact
Authors: Christopher Spalding and Fred C. Adams
First Author’s Institution: Yale University
Status: Published in PSJ
Mercury is a bit of an oddball compared to the other terrestrial planets. Because of its proximity to the Sun, Mercury doesn’t have an atmosphere, only a “surface-bound exosphere” of gas particles on ballistic trajectories. Under the surface, Mercury has an iron core that extends to more than 80% of its radius, compared with just 50% for Earth.
Many theories have been proposed to explain how Mercury ended up as the planet with the largest core compared to its size. One idea is that Mercury formed with a silicate mantle that was blasted away by asteroid impacts. Another puts forth that as the planets formed from the protoplanetary disk orbiting the Sun, high temperatures sorted out the silicates and iron, so Mercury formed in ...