SEM-EDS elemental map of YDB magnetic grain. Upper left, SEM image of magnetic grain. SEM-EDS elemental map and separate spot analysis (yellow cross on upper left image) show that this highly reduced grain is composed of ~97% Fe, 2% O, and ~1% Ni, suggesting a possible extraterrestrial origin. Si and Al were undetectable in the grain itself but were detected in surface debris shown by the whiter-colored areas in the two lower right images. Elemental composition is provided in Supplementary Fig.&nbsp; S7 .