Lunar soil samples from Chang’e missions reveal history of organic matter

An international research team has made important discoveries from lunar soil samples brought back by China’s Chang’e-5 and Chang’e-6 missions. Published in Science Advances, the study uncovers the evolutionary history of organic matter in the solar system.

Led by the Chinese Academy of Sciences and in partnership with the University of New Mexico, the team systematically identified, for the first time, multiple nitrogen-rich organic compounds in lunar soil grains.

These findings show that the Moon records the history of organic material delivery from asteroids and comets, while also preserving evidence of how impacts and irradiation altered these materials.

In the early solar system, such celestial bodies served as “couriers,” transporting vital elements such as carbon and nitrogen to planets. Although Earth’s geological activity has erased these records, the Moon functions as a “time capsule,” holding onto this ancient chemical history.

Researchers used microscopic and spectroscopic techniques to characterize the chemical bonding and isotopic compositions of the organic matter. They discovered that the isotopic signatures of these lunar organics are lighter than those found in typical asteroid samples.

This suggests that impacts by extraterrestrial bodies triggered the decomposition and migration of organic materials, which then condensed onto mineral surfaces, forming new structures.

The study has notably identified for the first time the presence of solar wind implantation signatures in lunar organic matter. Variations in hydrogen isotopic compositions observed near the grain surfaces suggest prolonged exposure to solar wind irradiation. Hao Jialong, the corresponding author, noted that these “fingerprints” effectively rule out terrestrial contamination.

This research establishes a strong analytical framework for future missions, such as Tianwen-2, and offers new insights into how small-body materials evolved and were delivered throughout the early solar system.