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Published 2010 | public
Book Section - Chapter

Terrestrial Planet Interiors

Abstract

The discovery and study of exoplanets has always motivated the question of the existence and nature of terrestrial exoplanets, especially habitable planets. Exoplanet mass and radius measurements (yielding average density) are possible for a growing number of exoplanets, including terrestrial planets. The mass and radius provide a constraint for terrestrial planet interior models and, via models, enable interpretation of a planet's bulk composition. This chapter describes the fundamental equations for calculating the interior structure of terrestrial planets (including silicate-rich, iron-rich, and water-rich planets). A detailed description of interior structure models is given, with emphasis on the equation of state. High-pressure experimental measurements are needed to understand the internal structure and evolution of massive terrestrial exoplanets. Interpretation of low-mass planet interiors are fundamentally limited by degeneracies, because there are only two data points per planet: mass and radius. For example, large terrestrial planets having a massive primordial atmosphere of H_2, and He cannot be distinguished from planets having dominant internal H_2O layers based on the mass and radius alone. The occurrence of plate tectonics on exoplanets more massive than Earth is a controversial question, and, although unanswered, this chapter addresses the relationship between plate tectonics and thermal convection. As more and more low-mass exoplanets are being discovered, mass vs. radius statistics will build up. The hope for terrestrial exoplanet mass and radius measurements is that unique populations will emerge from statistics, helping us to understand planet formation and evolution.

Additional Information

© 2010 University of Arizona Press. This work has been carried out at the Jet Propulsion Laboratory-California Institute of Technology, under contract with the National Aeronautics and Space Administration. C.S. acknowledges JPL R&TD support. J.M.J. acknowledges the National Science Foundation (0711542 and CSEDI 0855315) and Caltech for partial support of this work.

Additional details

Created:
August 22, 2023
Modified:
October 20, 2023