The MESSENGER spacecraft, “collected data providing important insights into the structure, chemical makeup, and compositional diversity of Mercury.” The atypically low ratios of these Mercury measurements were contextualized and visualized by plotting previously known values of O wt% vs Si wt% from large compendia of Lunar and Martian data, meteoritic samples, and terrestrial rock data downloaded from PetDB.
Fig 1. Plot of O abundance (wt %) versus Si abundance (wt %) for various chondrite and achondrite meteorites as well as mafic rocks from Earth, Moon, and Mars. A black line representing the measured O/Si weight ratio from MESSENGER GRS of 1.2 ± 0.1 is also displayed with the error envelope represented by a black dashed line
McCubbin, F., et al., 2017, A Low O/Si Ratio on the Surface of Mercury: Evidence for Silicon Smelting?, Journal of Geophysical Research, Planets, vol. 122, pp.2053-2076, DOI:10.1002/2017JE005367