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47070.  Sat Jan 21, 2006 5:20 pm Reply with quote

Another kind of dust completely, but there might be a link to dust mites.

Nasa's Stardust probe has recently captured grains of dust from comet Wild 2 using a substance called aerogel, otherwise known as 'frozen smoke' or 'glass foam'.

Like glass, it is made of silicon oxide, but it's 1000 times less dense than glass - in fact 99.8% air - and is the lowest-density solid in existence. A gram of it can spread out over 3000 square metres. However, it can hold up more than 4000 times its own weight. It is also almost 40 times better than fibreglass at insulating heat and sound. A one-inch thick pane can insulate as well as 15 panes of glass with air trapped between them.

The reason it was used by Stardust is that the density is so low that it could slow down and capture comet dust without damaging it. Other materials would have caused the dust to vapourise or change shape but aerogel allowed the dust to make tracks and embed itself.

Aerogel was invented by Steven S Kistler of the College of the Pacific in Stockton, California, in the 1930s but disregarded until scientists needed something in which to store rocket fuel.

Source - today's Guardian.


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