1. Arizona State University, 2. Carnegie Observatories, 3. Observatorio Nacional, 4. Ohio State Univ.
The composition of rocky planets has major implications for their core sizes and their ability to sustain plate tectonics. We report on our measurements of the major rock-building elements O, Mg, Si and Fe for the host stars of known small planets using high-resolution spectra from the APOGEE survey. We discuss the role that these abundance ratios play in the mantle minerology and core formation and speculate on the consequences for habitability of rocky exoplanets.