Chinese scientists discover mushroom-shaped crystal growth pattern in Chang'e-5 lunar samples

Chinese researchers have discovered a peculiar crystal growth pattern in the lunar samples from the Chang'e-5 mission. Specifically, chromite nanocrystals can grow outward from the surface of olivine like "mushrooms after rain," the research team told the Global Times on Wednesday. The findings may serve as an indicator of extreme non-equilibrium crystallization, providing a reference for future studies into crystal growth mechanisms on airless celestial bodies and in other extreme conditions.

The related research results were published in the first 2025 issue of the international academic journal American Mineralogist. 

Crystallization is a crucial physicochemical process that influences the majority of properties of substances in a condensed state. Progress in crystallography and crystal chemistry plays a significant role in enhancing human understanding of geological processes, materials science and biogeochemistry. 

Classical crystal growth theories are all based on Earth materials, while the crystallization processes in extraterrestrial environments remains unknown. For example, the moon, the closest celestial body to Earth, lacks atmospheric protection and is constantly bombarded by micrometeoroids and various high-energy particles. Under the extreme high temperatures and pressure generated by these impacts, the grain size, morphology, growth patterns and mineral composition of lunar crystals show clear differences compared with those on the Earth. 

Through a detailed study of lunar soil samples from the Chang'e-5 mission, the research team led by academician He Hongping from the Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, discovered a peculiar crystal growth phenomenon in lunar samples. Specifically, chromite nanocrystals can grow outward from the surface of olivine like "mushrooms after rain," according to a press release from the research team. 

To explore the mechanisms behind the phenomena, the research team conducted micro-nanoscale mineralogical research on the lunar breccia from the Chang'e-5 mission, using advanced electron microscopy and related analysis methods.

This study proposes a novel growth mechanism occurs under extreme non-equilibrium conditions, which utilizes impure ions within the original phases to generate new mineral phases at the heterogeneous interfaces between original phases. This finding demonstrates for the first time that oriented attachment of crystals can occur not only in homogeneous systems but also in heterogeneous systems. This insight provides an important supplement and expansion to the existing non-classical growth mechanism theory.

Given the frequent meteoroid impacts on the moon, this mechanism may occur widely in the lunar weathering layer, the team said, thus affecting the mineral composition and elemental distribution on the lunar surface. Moreover, the appearance of these "mushroom" structures may serve as an indicator of extreme non-equilibrium crystallization, providing scientists a reference for future studies on crystal growth mechanisms on airless celestial bodies and in other extreme conditions.