XCT slice 688 of the Murchison USNM 5487 chip. (A) XCT scan in vacuum. (B) XCT scan in xenon at 450 PSIG; the highly attenuating gas has infiltrated the highly porous matrix, making it appear brighter relative to the chondrules. (C) XCT-derived porosity showing the highly porous matrix and locally highly porous FGRs (white arrows); the per-voxel 2σ error is 13.6%. (D) Isolated FGR porosity data showing porosity variations around several FGRs.