The amino acid and polycyclic aromatic hydrocarbon compositions of the promptly recovered CM2 Winchcombe carbonaceous chondrite

Abstract

The rapid recovery of the Winchcombe meteorite offers a valuable opportunity to study the soluble organic matter (SOM) profile in pristine carbonaceous astromaterials. Our interests in the biologically relevant molecules, amino acids-monomers of protein, and the most prevalent meteoritic organics-polycyclic aromatic hydrocarbons (PAHs) are addressed by analyzing the solvent extracts of a Winchcombe meteorite stone using gas chromatography mass spectrometry. The Winchcombe sample contains an amino acid abundance of ~1132 parts-per-billion that is about 10 times lower than other CM2 meteorites. The detection of terrestrially rare amino acids, including a-aminoisobutyric acid (AIB); isovaline; b-alanine; a-, b-, and c-amino-n-butyric acids; and 5-aminopentanoic acid, and the racemic enantiomeric ratios (D/L = 1) observed for alanine and isovaline indicate that these amino acids are indigenous to the meteorite and not terrestrial contaminants. The presence of predominantly a-AIB and isovaline is consistent with their formation via the Strecker-cyanohydrin synthetic pathway. The L-enantiomeric excesses in isovaline previously observed for aqueously altered meteorites were viewed as an indicator of parent body aqueous processing; thus, the racemic ratio of isovaline observed for Winchcombe, alongside the overall high free:total amino acid ratio, and the low amino acid concentration suggest that the analyzed stone is derived from a lithology that has experienced brief episode(s) of aqueous alteration. Winchcombe also contains 2-to 6-ring alkylated and nonalkylated PAHs. The low total PAHs abundance (6177 ppb) and high nonalkylated:alkylated ratio are distinct from that observed for heavily aqueously altered CMs. The weak petrographic properties of Winchcombe, as well as the discrepancies observed for the Winchcombe SOM content-a low total amino acid abundance comparable to heavily altered CMs, and yet the high free:total amino acid and nonalkylated:alkylated PAH ratios are on par with the less altered CMs-suggest that Winchcombe could represent a class of weak, poorly lithified meteorite not been previously studied.

The formation and aqueous alteration of CM2 chondrites and their relationship to CO3 chondrites: A fresh isotopic (O, Cd, Cr, Si, Te, Ti, and Zn) perspective from the Winchcombe CM2 fall

“…Just over 300 g of debris and dust were produced when a fragment of the meteorite impacted the Wilcock family driveway in Winchcombe, Gloucestershire (Russell et al, 2023). The actions taken by the Wilcock family in collecting up this material so quickly and cleanly after its fall means that Winchcombe is one of the least terrestrially contaminated CCs in our collections (Russell et al, 2023) and so invaluable for a wide range of studies, particularly those in which potential contamination is a major issue (Chan et al, 2023;Sephton et al, 2023).…”

Insoluble macromolecular organic matter in the Winchcombe meteorite

“…Raman spectroscopy was initially conducted on an exposed surface from the interior of the allocated Winchcombe stone, and a ~10 mg portion was then subsampled from the powdered meteorite for thermal extraction/pyrolysis–gas chromatography–mass spectrometry (pyrolysis–GC–MS). Soluble organic matter (SOM) was extracted using hot water from the remaining powdered sample, and the SOM content is reported in a separate study (Chan et al., 2023). Chips from two separate pieces of Winchcombe (BM 2022,M1‐85 and BM 2022, M1‐86) were used for stepped combustion.…”

Recovery and curation of the Winchcombe (CM2) meteorite

“…Aluminum foil is routinely used to collect Antarctic friable carbonaceous chondrites and also for the Sutter's Mill CM fall (Jenniskens et al, 2012). The total recovered from this site was ~319 g. Samples were also collected of the surrounding soil and vegetation, and data from this material are discussed in Chan et al (2023).…”

“…It was collected using nitrile gloves and geological sample bags. Ground samples were also collected of the surrounding soil and vegetation, and data from this material are discussed in Chan et al (2023). The UK was in lockdown due to the COVID-19 pandemic at the time; this meant that only essential travel was allowable by law and placed severe constraints on the ability for people to mix indoors and within cars.…”