The Effects of Mg/Si on the Exoplanetary Refractory Oxygen Budget

Cayman T. Unterborn1,3 and Wendy R. Panero2
Astrophysical Journal 845, 61 Link to Article [https://doi.org/10.3847/1538-4357/aa7f79]
1School of Earth and Space Exploration, Arizona State University, Tempe, AZ 85287, USA
2School of Earth Sciences, The Ohio State University, Columbus, OH 43210, USA
3SESE Exploration Fellow.

Solar photospheric abundances of refractory elements mirror the Earth’s to within ~10 mol% when normalized to the dominant terrestrial-planet-forming elements Mg, Si, and Fe. This allows for the adoption of solar composition as an order-of-magnitude proxy for Earth’s. It is not known, however, the degree to which this mirroring of stellar and terrestrial planet abundances holds true for other star–planet systems without determination of the composition of initial planetesimals via condensation sequence calculations and post condensation processes. We present the open-source Arbitrary Composition Condensation Sequence calculator (ArCCoS) to assess how the elemental composition of a parent star affects that of the planet-building material, including the extent of oxidation within the planetesimals. We demonstrate the utility of ArCCoS by showing how variations in the abundance of the stellar refractory elements Mg and Si affect the condensation of oxygen, a controlling factor in the relative proportions of planetary core and silicate mantle material. This thereby removes significant degeneracy in the interpretation of the structures of exoplanets, as well as provides observational tests for the validity of this model.

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