High-resolution TEM, selected-area electron diffraction, and FFT pattern of pyrrhotite grain in RA-QD02-0125. A high-resolution TEM of the space-weathered pyrrhotite grain in RA-QD02-0125 (left). The outermost surface of the grain is armored with a thin layer of nanophase Fe metal grains. The selected-area electron diffraction from the core of the grain (labeled ‘core,’ upper right) shows strong superstructure reflections (arrowed) that are absent in the fast-Fourier transform (FFT) pattern from the rim (labeled ‘rim,’ lower right). In addition, the FFT pattern from the rim shows reflections that are consistent with the (110) spacings of iron metal (small dashed circles).