A new material developed by JPL/NASA with amazing insulating properties and a ghostly appearance like an hologram, even though it is very solid.
Aerogel will be used on the STARDUST spacecraft to capture comet particles from Comet Wild 2.
Check out the pictures in the link below.
It is 99.8% Air
Provides 39 times more insulating than the best fiberglass insulation
Is 1,000 times less dense than glass
Was used on the Mars Pathfinder rover
http://stardust.jpl.nasa.gov/tech/aerogel.html
http://eande.lbl.gov/ECS/aerogels/saphoto.htm
Aerogel is the lightest and lowest-density solid known to exist. It is typically 50-99.5% air, yet can hold (theoretically) 500 to 4,000 times its weight in applied force. Aerogel can have surface areas ranging from 250 to 3,000 square meters per gram, meaning that a cubic inch (2.5 cm x 2.5 cm x 2.5 cm) of aerogel flattened-out (again theoretically) would have more surface area than an entire football field! Aerogel's superlow density makes it useful as a lightweight structural material, and its superhigh internal surface area makes it a superinsulating solid material