Fig. 2. Cross-sections of three Ryugu grains showing typical surface modifications on the phyllosilicate-rich matrix.
a, The cross-section A0104–02306901 was prepared from the grain A0104–02306900 collected at the first touchdown site. It has a smooth layer that forms a ~100-nm-thick continuous layer covering the surface of the grain. The phyllosilicate-rich matrix is present below the smooth layer. A yellow dashed curve indicates the cross-section of the sample surface. The boundary between the smooth layer and the phyllosilicate-rich interior is indicated by an orange dashed curve. b, The cross-section C0105–03003701 was prepared from the grain C0105–03003700 collected at the second touchdown site. A frothy layer containing abundant vesicles (darker circles) and <50-nm-size brighter spots (Fe-Ni sulfide beads) covers the surface of this grain. The thickness of the frothy layer varies considerably locally from <100 nm to >500 nm. A yellow dashed curve indicates the cross-section of the sample surface. C-depo denotes carbon depositions to protect the surface of the samples during FIB processing. c, An enlarged image of a frothy layer in a cross-section A0104–02802202. The frothy layer contains many tiny (<20 nm across) blisters (vesicles just below the surface) on its surface. These are high-anglular dark-field scanning transmission electron microscope images, in which materials with higher average atomic numbers are brighter than those with lower average atomic numbers.