Electron microscope studies of particles on sampling surfaces recovered from space with sounding rockets

Four Luster sounding rocket payloads have exposed sampling surfaces in the outer atmosphere during meteor showers and returned them in an attempt to collect micrometeoroids for analysis. Numerous surfaces designed for electron microscope analysis were exposed during the flights. These surfaces were shadowed before and after flight with choromium to aid in the detection of contaminants. In addition, rigorous contamination control procedures were enforced to maintain cleanliness of the samples. Electron microscope studies of particles on these surfaces indicate that fewer submicron-sized micrometeoroids are reaching the earth than previous experiments indicated. The collection of possible extraterrestrial particles must be much less than 20–80 particles/cm² in contrast to predictions of 500/cm² deduced from previous studies. Attempts using a conventional electron microscope to distinguish space particles by their physical appearances alone were unsuccessful.