Image Caption: This is a scanning electron microscope image of an interplanetary dust particle that has roughly chondritic elemental composition and is highly rough (chondritic porous: "CP"). CP types are usually aggregates of large numbers of sub-micrometer grains, clustered in a random open order. The authors of this figure are Don Brownlee, University of Washington, Seattle, and Elmar Jessberger, Institut für Planetologie, Münster, Germany. (Wikipedia)