PLANETESIMALS HERE. PLANETESIMALS THERE. PLANETESIMALS EVERYWHERE (Invited Presentation)

Meteorites provide a potential link for understanding how planetary building blocks, or planetesimals, influence the compositions of exoplanet atmospheres. We have developed a novel experimental approach to precisely determine the composition of gases released during meteorite outgassing in order to constrain the initial composition of planetary atmospheres – a key constraint for interpreting chemical signatures from exoplanet atmosphere observations (Thompson et al., LPSC #1205). From our first study, we determined that if a planet’s bulk composition is similar to that of CM chondrites, its initial outgassed atmospheric composition is expected to be water-rich with significant amounts of CO, CO₂, H₂, and H₂S. This work assumes that meteorites can be used as analogs for planetesimals in exoplanetary systems. Here, we examine this assumption in detail. We discuss what is known about planetesimals here, in our solar system, and what is known about planetesimals there, in other solar systems, and address whether meteorites can be used as an analog to study planetesimals everywhere. To answer this question, we look to the composition of stars because this is the most direct way to study the composition of the planetesimals that formed around them. Primitive meteorites and the Sun share striking similarities in composition indicating that planetesimals form from a disk similar in composition to their host star. Astronomers can measure an impressive number of elements in other stars. When we survey the composition of various stars, including solar twins and exoplanet host stars, we find that meteorites can indeed be useful analogs for planetesimals, especially around Sun-like stars and stars with C/O ratios consistent with oxygen-rich environments. The compositions of polluted white dwarf stars, the leftover cores of low-mass stars whose atmospheres show enrichments in elements heavier than hydrogen and helium, provide additional support for meteorites as possible analogs to planetesimals around other stars.