Sample Collection

	STARDUST collection tray with blocks of silica aerogel being loaded.
	Porous interplanetary dust particle MIR1, captured in silica aerogel in low-Earth orbit on the Mir Space Station. The grain has been removed from the aerogel, thin sectioned using a diamond blade of an ultramicrotome, and is being imaged in a transmission electron microscope. The scale bar at lower right measures 5 micrometers.

The sample harvest from Stardust consists of thousands of cometary dust particles measuring less than 100 µm each, and ~100 interstellar dust grains of mostly sub-micron size. The total mass of returned sample will be approximately 1 mg. The comet samples were collected during a 6.1 km/s (relative velocity) flyby of Comet Wild-2. The collector tray consists of blocks of 1 and 3 cm thick low-density, microporous silica aerogel mounted in modular aluminum cells. One side of the tray was used to collect samples during the comet encounter, and the opposite side was used for interstellar collection.

On this mission, both comet coma samples and the contemporary interstellar grains were captured at high velocity with minimal heating and other effects of physical alteration. Particle collection at this speed has been extensively demonstrated in laboratory simulations, Shuttle flights and on the MIR Space Station, and we have shown that the comet dust collection can be done with acceptable levels of sample alteration. Techniques were developed for the removal and analysis of captured grains from silica aerogel prior to the comet samples return. The state of captured interstellar dust prior to return was less secure because of the small particle size, higher impact velocity, and unknown material properties.