Laboratory studies of interplanetary dust

The paper summarizes laboratory studies of interplanetary dust samples that have been collected from the stratosphere in the form of micrometeorites between 2 and 50 microns in size and from the sea floor in the form of particles between 100 and 3000 microns in size. Experimental results are reviewed for analyses of bulk elemental and isotopic compositions, measurements of noble gases, structure, and mineralogy. The results are shown to suggest that many of the collected particles are probably of cometary origin and that, if so, comets are fine-grained aggregates of nonvolatile building blocks and ice. Possible reasons for the lack of solar-flare tracks in the particles are briefly discussed.