What Is Aerogel and Why Is It Called Frozen Smoke?

The Lightest Solid Ever Made

Aerogel is a synthetic ultralight material made by replacing the liquid in a gel with gas, resulting in a solid that is up to 99.8% air by volume — making it the least dense solid material ever created and earning it the nickname “frozen smoke.”

Almost Entirely Nothing

Look at a block of silica aerogel and your eyes will argue with your brain. It appears translucent, wispy, almost ghostly — yet it is a genuine solid you can hold in your hand. The secret is in its structure. The entire physical skeleton of the material accounts for less than one percent of the space it occupies. Everything else is air, trapped inside a web of nanoscale pores so fine they are invisible to the naked eye. Despite being almost nothing, aerogel can support up to 4,000 times its own weight. A small piece that weighs almost nothing can bear a load that would flatten ordinary insulating foam entirely.

Why Aerogel Insulates Better Than Air Itself

One of aerogel’s most counterintuitive properties is its thermal insulation. It does not just match still air as an insulator — it outperforms it. The reason comes down to pore size. Aerogel’s internal pores measure between 20 and 50 nanometers across. Gas molecules need room to move and collide in order to transfer heat, and aerogel’s pores are simply too small to allow that process to happen efficiently. Heat has almost nowhere to go. The result is an insulating material that performs better than almost any substance found in nature, including air itself at standard pressure.

NASA’s Secret Weapon

Aerogel’s extreme properties made it an obvious choice for space exploration. NASA used silica aerogel as thermal insulation on the Mars Pathfinder rover, protecting its electronics from surface temperatures that plunge as low as −110 degrees Celsius. Without aerogel shielding, the rover’s systems would have failed in the brutal Martian night.

NASA also packed aerogel aboard the Stardust spacecraft for an entirely different mission: catching comet particles. These particles were traveling at approximately 6 kilometers per second — fast enough to vaporize on contact with most materials. Aerogel’s ultra-low density allowed it to decelerate the particles gradually rather than obliterating them on impact, trapping intact grains of ancient comet dust for scientists to study back on Earth. It was the first time in history that cometary material had ever been collected and returned for analysis.

From Labs to the Real World

Aerogel is no longer confined to space missions. Industrial and commercial applications have expanded steadily as manufacturing costs have come down. It is used in high-performance building insulation, cold-weather clothing, pipeline insulation in the oil and gas industry, and even in some footwear designed for extreme cold. Flexible aerogel blankets — composite materials that embed aerogel in a fibrous mat — have made the material far easier to handle than the fragile pure-silica blocks that first put it on the map.

Researchers continue to develop new formulations. Carbon aerogels, graphene aerogels, and metallic aerogels push the boundaries even further, with some achieving densities lower than that of air at sea level. The material that looks like nothing continues to find ways to do nearly everything.