Soluble Organic Compounds and Cyanide in Apollo 17 Lunar Samples: Origins and Curation Effects

We analyzed 12 Apollo 17 samples through the Apollo Next Generation Sample Analysis (ANGSA) program to determine the abundances of a variety of compound classes, including amino acids, aldehydes, ketones, amines, carboxylic acids, and cyanide-releasing species. Analyzed samples included portions of double drive tube 73001/73002, the bottom half of which (73001) was hermetically sealed under lunar vacuum, as well as lunar regolith samples from three different illumination environments that had been curated frozen for similar to 50 years. Consistent with previous results, we detected low levels of amino acids in the hot-water extracts of most samples (0.55-12.03 nmol/g in unhydrolyzed samples; 0.53-72.38 nmol/g after acid hydrolysis of the extracts). We also detected one-carbon and two-carbon species of amines, aldehydes, and carboxylic acids (i.e., methylamine, ethylamine, formaldehyde, acetaldehyde, formic acid, acetic acid) not previously reported in lunar samples, as well as insoluble cyanide-forming species. Although these compounds are potential precursor molecules for amino acids, no specific precursor relationships could be determined. Nylon contamination was the likely source of some amino acids. Abundances of some species (e.g., cyanide) decreased with increasing depth in the drive tube, suggesting that exogenous delivery and concentration mechanisms near the surface outweighed surface degradation processes. In addition, we observed the potential cold trapping of volatile amines in the persistently shadowed samples analyzed. Finally, we noted the effects of different curation conditions; hermetic sealing appeared to preserve higher amounts of volatile compounds, while frozen curation did not have a noticeable preservation effect on the organic volatiles analyzed here. The Moon's surface may contain organic chemicals similar to those used by life on Earth, but previous studies have been limited. Some of the Moon rocks and dirt collected in 1973 by the Apollo 17 astronauts were set aside for future generations to study after new techniques could be developed. Recently, after nearly 50 years in curation, some of these samples were made available to researchers, including samples that had been sealed by astronauts on the lunar surface and not exposed to the Earth's atmosphere, as well as samples that were stored in a freezer after return to Earth. We examined these samples along with other Apollo 17 samples to search for small organic chemicals such as amino acids (like those in proteins in life on Earth) and related molecules. We found small amounts of volatile compounds such as formaldehyde, which had not previously been detected in Moon samples. We also found that storing the samples in special sealed containers may better preserve volatile chemicals, while freezing did not have a strong effect on the chemicals we examined. These results help us understand the chemical environment of the Moon and provide lessons for the storage of future returned samples. Low (nmol/g) abundances of volatile organic compounds were detected in specially curated Apollo 17 samples We observed amino acids, cyanides, amines, aldehydes, ketones, and carboxylic acids, including some not previously known in lunar samples Hermetically sealed curation better preserved certain volatile compounds, while frozen curation may reduce organic contamination