The Role of Core Structure in Super-Earths on Exoplanet Habitability

Artist depiction of a Super-Earth. Image credit: NASA/JPL-Caltech/R. Hurt (SSC)

Magnetic fields around planetary bodies are important factors for understanding the habitability of other worlds because they reduce atmospheric loss and protect the surface of the planet from radiation. The coexistence of a solid and liquid metallic core is typically the main driver in maintaining a magnetic field around a planet and, until now, it was unknown whether solid and liquid cores existed within the super-Earths (large rocky exoplanets) orbiting stars outside our solar system. The team of Asmaa Boujibar, Peter Driscoll, and Yingwei Fei from the Carnegie Institution for Science in Washington, D.C. modeled the internal structure of super-Earths to investigate the conditions required for the presence of a crystallizing core across a range of super-Earth masses and core-mantle mass fractions using recent data on the melting properties of deep-mantle minerals (such as postperovskite) at ultrahigh pressures. Their results show that large super-Earths with large core masses are most likely to be partially molten. Furthermore, their results show that the presence of a partially molten inner core in large super-Earths is likely to be accompanied by the prolonged partial melting of their lowermost mantles. As such, it is likely that large super-Earths are able to maintain a magnetic field that would shield the surface from cosmic radiation and promote habitability. READ MORE