Remanent crustal strain on Mars in non-poikilitic olivine of NWA 7721

We present a multiscale, non-destructive analysis of non-poikilitic olivine in the shergottite NWA 7721 using dark-field X-ray microscopy, electron backscatter diffraction, and 2D micro-X-ray diffraction. We report striking bimodal microstructures within a single olivine crystal: fine Type 1 subgrains (around 5 μm), weakly oriented, and nearly strain-free; coarser Type 2 subgrains (>15 μm), aligned, and strongly strained. Layered DFXM data reveal slip-band features in Type 2 that are absent in Type 1. This bimodal microstructure, not observed in other Martian meteorites, including the paired NWA 1950 and ALH A77005, points to a heterogeneous response to impact at the crystallographic scale. We interpret Type 1 as shock-assisted recrystallites and Type 2 as relic partitioned from a highly deformed parental grain with a pre-existing fabric. The subsequent shock wave imposed a rapid load-release cycle that generated heterogeneous deformation within the crystal. Highly strained regions underwent recrystallization to form Type 1 subgrains, whereas less-strained domains retained deformation structures as Type 2. Grain-growth constraints limit the post-shock heating to ≈2.3 s, consistent with rapid quenching. Together, these observations illustrate a dynamic Martian crustal activity in the Late Amazonian and demonstrate DFXM, combined with EBSD and micro-XRD, as a promising tool for resolving complex fabrics in 3D.