Low voltage scanning electron microscopy of interplanetary dust particles

Interplanetary Dust Particles (IDPs) are a relatively new class of extraterrestrial materials which are collected by high-flying aircraft in the stratosphere. The particles, ∼1.0-50 μm in size, enter the earth's atmosphere at ballistic velocities, but are sufficiently small to be decelerated without burning up. IDPs commonly have solar elemental abundances, and are thoughfto have undergone very little differentiation since the formation of the solar system. While these materials are called “particles,” they are in fact aggregates of a variety of mineral phases, glass, and carbonaceous material. Grains within IDPs commonly range from a few microns to a few tens of nanometers. The extraterrestrial origin of IDPs has been established by the discovery of solar flare tracks in some mineral grains, and recent D/H isotopic ratios recorded from individual particles. The source and formational history of the particles is a topic of active research. At present, the primary means of screening and classifying IDPs is Scanning Electron Microscopy, although a variety of electron microbeam and X-ray techniques is used for subsequent analysis.