The primary objective of the STARDUST mission is to capture both comet coma samples and contemporary interstellar grains moving at high velocity with minimal heating and other effects of physical alteration. To achieve this a new intact capture technology has been developed over the past decade specifically for comet flyby sample return missions in which hypervelocity particles are captured by impact into under-dense, microporous media known as aerogel.
This is not like conventional foams, but is a rather special porous material that has extreme microporosity at the micron scale. Aerogel is composed of individual features only a few nanometers in size, linked in a highly porous dendritic-like structure.
This exotic material has many unusual properties, such as uniquely low thermal conductivity, refractive index, and sound speed, in addition to its exceptional ability to capture hypervelocity dust.
Aerogel is made by high temperature and pressure critical point drying of a gel composed of colloidal silica structural units filled with solvents. Over the past several years, aerogel has been made and flight qualified at the Jet Propulsion Laboratory.
When hypervelocity particles are captured in aerogel they produce narrow cone-shaped tracks, that are hollow and can easily be seen in the highly transparent aerogel by using a stereo microscope. The cone is largest at the point of entry, and the particle is collected intact at the point of the cone.
Aerogel Collector Grid
(above)
Dr. Peter Tsou, JPL (above)
A captured particle. Aerogel
Magnified 6500x (above)
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