Impact-processed nitrogen-bearing organics in Chang'e-5 and Chang'e-6 lunar regolith

Area of Science:

• Lunar science
• Astrochemistry
• Geochemistry

Background:

• The Moon preserves a record of extraterrestrial organic matter delivered by impacts.
• Understanding lunar organics provides insights into early solar system chemistry and delivery processes.

Purpose of the Study:

• To characterize the diverse organic phases found on lunar regolith grains.
• To investigate the origin and chemical processing of lunar organic matter.

Main Methods:

• Analysis of lunar regolith grains returned by Chang'e-5 and Chang'e-6 missions.
• Characterization of organic matter using techniques to identify phases, functional groups (N-, O-bearing, amide linkages), and isotopic compositions (δD, δ¹³C, δ¹⁵N).
• Assessment of solar wind implantation signatures.

Main Results:

• Diverse organic phases (particle-like, adhering-like, inclusion-like) were identified on lunar regolith grains.
• Organics are predominantly amorphous carbon-like with N- and O-bearing functionalities and amide linkages.
• Lunar organics exhibit more negative isotopic values (δD, δ¹³C, δ¹⁵N) compared to carbonaceous chondrites and asteroids, suggesting impact-induced processing.
• Evidence of solar wind implantation indicates long-term surface exposure.

Conclusions:

• Asteroid and comet impacts delivered and chemically processed organic matter on the lunar surface.
• Impacts generated N- and O-bearing functionalities in lunar organics.
• The Moon serves as a valuable archive for studying extraterrestrial organic matter and its evolution.