Why was aerogel used on Stardust?
A. Aerogel is endowed with remarkable qualities, including being 39 times more insulating than the best fiberglass insulators. For Stardust, aerogel’s most important characteristic is its ability to slow down and preserve particles traveling at high speed. The cometary and interstellar dust particles encountered by Stardust were traveling ten times at speeds of around 20 kilometers (12 miles) per second relative to the spacecraft. Normally, they would be pulverized or even evaporate when encountering a solid object in their way. But aerogel is able to slow the particles down to a halt within the space of a few dozen microns, and preserve them better than any known substance.
