Cyanide Abundance and Soluble Organic Composition in Highly Aqueously Altered CM Chondrites

Spectroscopic measurements of regolith collected from asteroid Bennu identified magnesium-rich phyllosilicates indicative of high degrees of aqueous alteration, which resemble the most aqueously altered carbonaceous chondrites. Here we report on the complex distribution of soluble organic compounds of four highly aqueously altered CM chondrites of petrologic types 1 and 1/2 using electrospray ionization ultrahigh-resolution orbitrap mass spectrometry and Kendrick mass analysis. A significant portion of the assigned molecular formulas belonged to the CHN ₁ and CHN ₂ classes, which exhibited extensive alkylation and a wide range of double bond equivalent values and may be products from formose-like reactions involving formaldehyde and ammonia. We also report cyanide abundances in acid digestion distillates ranging from 15–55 nmol·g ^–1 using capillary flow liquid chromatography–orbitrap mass spectrometry. We suggest that cyanide-containing species in these meteorites were most likely transition metal–cyanide complexes because we determined that only a very small fraction of acid-releasable cyanide was due to simple metal–cyanide solids. This study indicates that regolith collected from asteroid Bennu will likely contain a low abundance of (acid-releasable) cyanide species among a complex distribution of soluble organic compounds.