Astro-Seminar: More than MgSiO3: What rocky planets are made of

Exoplanet observations tell us the mass and radius of a planet, and thus the bulk density, but many combinations of materials can meet the same constraint on this bulk density. Further, Earth is a volatile-poor planet, such that its atmosphere or ocean mass would never make a dent in even the best bulk density observations. To infer anything about the volatile contents and more detailed silicate composition of a presumably-rocky exoplanet, we therefore take advantage of the wealth of knowledge from the geosciences. In this seminar, I will introduce how we use geological modelling, constrained through a long history of experiments, to understand the compositional diversity of presumably-rocky exoplanets. I will also discuss why it matters that these planets are more than MgSiO3: that is, certain elements have an immense power over the cycling of matter and energy through the complex systems that are planets.