A Celestial Puzzle: The Search for Polycyclic Aromatics

Polycyclic aromatics, fascinating compounds found throughout the universe, have long eluded researchers on the Moon. Their prevalence in meteorites and the interstellar medium raises the question: can we uncover their secrets on lunar soil?

Chang’e 5 Reveals Exciting Discoveries!

Recent analysis of lunar soil samples from China's Chang’e 5 mission has revealed astonishing concentrations of polycyclic aromatics, measuring between 5.0 and 9.2 µg/g, with an average of 7.4 ± 1.4 µg/g. These compounds exhibit condensed structures remarkably similar to graphene sheets, standing out as distinctly different from terrestrial sources like wood char, soot, and kerogen.

The Mystery of Carbon Isotope Enrichment

What's more intriguing is the stable carbon isotope composition found within these lunar samples. The polycyclic aromatics exhibited a carbon-13 signature ranging from -5.0 ± 0.6‰ to +3.6 ± 1.3‰. This isotopic enrichment hints at a unique formation process that likely occurred during meteorite impacts, where non-aromatic organic matter was transformed into these complex compounds.

The Role of Meteorite Impacts in Lunar Regolith

Meteorite impacts not only introduce polycyclic aromatics but may also be critical for carbon accretion in lunar regolith. These larger, more stable molecules are less prone to degradation than smaller organic constituents like amino acids, which are often obliterated during such high-energy events.

A Step Towards Understanding Lunar Carbon Chemistry