Fig. 5.

Relationship of CHOMg signatures with different thermal processing stages of meteorites. An OPLS score scatter plot for 61 meteorites (CI, CK, CM, CO, CR, CV, EUC, H, L, LL, URE, and achondrite classes) with different inter- and intrameteorite class metamorphism stages is shown, based on the abundance and molecular diversity of CHOMg compounds. Details on the OPLS analysis are given in SI Materials and Methods and meteorite assignments are listed in Table S1. The box plots represent the averaged numbers of CHOMg molecular formulas for low and highly thermally altered meteorites, respectively. Thermal processing states vary from low to high along the x axis (first component), proceeding from negative to positive values. This first component (x axis) is related to the number and intensity of CHOMg molecular formulas, as represented in the box plot. The y axis (orthogonal to the first component) represents the proportion of oxygen atoms within the molecular formulas, as illustrated by modified van Krevelen diagrams of the most relevant loading values. Independent of the specimen, CHOMg signatures were observed with increased Mg-metalorganic diversity for thermally stressed meteorites. The two CM2 chondrites, Y-793321 and Y-86720, reported to be thermally metamorphosed (39), well-described meteorites, with respect to their shock history [Chelyabinsk (24) and Novato (23)], as well as the recently classified fall Sidi Ali Ou Azza (L4) and a very new German fall Stubenberg (LL6) were also assigned to the thermally stressed region.