Planets have a variety of chemical compositions, primarily accumulated during their formation from disks of material orbiting young stars. While these disks, in bulk, contain a complement of atoms similar to that of the average universe, the planets that they form generally do not. For example, Earth contains comparatively very little hydrogen though it is the most abundant element in the universe because Earth is hot enough that hydrogen gas can easily escape from its gravitational potential well. Observations with the Atacama Large Millimeter Array (ALMA) have revolutionized our understanding of the growth, migration, and chemical separation of solids in the outer regions of protoplanetary disks, and recent work with the James Webb Space Telescope (JWST) has begun to provide constraints on the chemistry of the inner regions of disks where terrestrial planets like Earth form. I will discuss what we know about the diverse compositions of planets orbiting stars other than the Sun, the diverse compositions of our own solar system’s planets, and the substantial recent progress that has been made toward connecting the chemistry of planet-forming environments with the chemistry of planets themselves.
