Impact-induced nano-sized rare mineral kuratite with correlated disorder on near and far sides of the Moon using 3DED method

Mineral structures record the formation and evolution of the Earth-Moon system. Here we report the discovery of correlated disorder in a silicate mineral kuratite [ideal formula Ca2Fe2+5Ti(Si,Al)6O20], which cannot be well documented by classical crystallography, in breccia clasts from near and far sides of the Moon. We employed advanced three-dimensional electron diffraction (3DED) method in combination with spherical aberration corrected transmission electron microscopy to thoroughly characterize its structural features. The results indicate that the kuratite, coexisting with dendritic pigeonite and ulvospinel, displays intricate correlated disorder features. These are characterized by alternating arrangements of five correlated site pairs confined within a single disordered layer. The occurrence of a vitrified dendritic pigeonite with similar composition suggests that kuratite formed during the impact induced melting-cooling processes. This finding shows consistency in impact-driven surface processes between the lunar near and far sides, while demonstrating the utility of advanced nanoscale crystallographic methods for decoding extraterrestrial mineral formation mechanisms.