To catch comets in space, Peter Tsou at JPL (one of the Halley team members) was determined to develop a means for what he called "intact capture". The idea was to use a "soft" capture material that would allow capture of particles without them being strongly heated.

Dr. Tsou began a long term development of materials that could capture small high speed particles. He started out using plastic foams to capture particles launched by a high speed "light gas gun" facility at the NASA Ames Research center. When this effort began it was widely thought that high speed "intact capture" was impossible and that the efforts were doomed to failure. Years of effort showed that it was possible and the program eventually evolved to use ultra low density aerogel, a material first developed at the University of the Pacific in the 1930's.

Silica aerogel is a wonderfully transparent material composed of very tiny silica particles bonded to each other to form an ultra low density microporous solid. Aerogel can be custom made with density that ranges from that of solid glass to that of air ( a thousand times less dense). This is a very strange material that is often referred to as frozen smoke because of it blue haze and near lack of mass. Peter made aerogel, tested it in many ground based experiments and flew in into space piggybacked onto a variety of experiments launched and recovered by the Shuttle.

Comet sample return missions using capture media were proposed many times but like most space proposals they were not accepted. Missions based on this idea were also proposed by Japan and Europe. The mission was finally selected as the fourth mission in the NASA Discovery program. The Discovery program was started by NASA to enable small low cost rapid development missions, a perfect match with the comet sample return via flyby concept.

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