The Analysis of Two Unique Micrometeorite Collections, and the Effect of Atmospheric Entry on Extra-Terrestrial Particles

Each year 40,000 tons of extra-terrestrial material reaches the Earth's surface as micrometeorites. These small (sub 1 mm) grains of material supply the majority of the extra-terrestrial flux reaching Earth. Unfortunately due to their small size they are often completely altered by their atmospheric passage and hence no-longer accurately reflect the mineralogy of their precursor grain. Despite the trauma of atmospheric entry, some dust grains remain intact through entry as a result of their trajectory and these may provide pristine samples of early solar system material, or material from a larger extra-terrestrial body. As such, micrometeorites provide an important vector for the analysis of the solar system's evolution and planetary science. This thesis examines the results of two novel micrometeorite collections, and the effects that atmospheric entry has on incoming micrometeorites. The two examined collections took place on the Kwajalein atoll in the mid-pacific and from the Halley VI research station in the Antarctic. Results recovered from these collections showed limited numbers of extra-terrestrial particles were recovered for further analysis from the Kwajalein survey, with none found on the Antarctic filters. Work was carried out to aid in the separation of extra-terrestrial material from the terrestrial debris often encountered in micrometeorite collections. Results from this work demonstrated the feasibility of, not only separating out material, but also provides possible links to micrometeorites and other meteoritic samples. This thesis also discusses the eight new extra-terrestrial candidates found upon the Kwajalein filters. The effects of atmospheric entry was investigated using specially designed equipment to allow passage through air for Light Gas Gun projectiles. Olivine projectile passage, through atmosphere, at hyper-velocity speeds was successfully carried out with the projectiles being recovered intact at speeds up to 2kms\(^{-1}\). At speeds exceeding 2kms\(^{-1}\), the force at launch was sufficient to disrupt the projectile prior to its passage through the atmospheric target. Results for these experiments show a trend of increasing surface damage at higher velocities and provides avenues for increasing projectile temperature at slower launch velocities.