As PaulHoule has pointed out, https://news.ycombinator.com/item?id=24179043 https://news.ycombinator.com/item?id=24179043 , Kapton is the final "gold foil" laye

As PaulHoule has pointed out, https://news.ycombinator.com/item?id=24179043 https://news.ycombinator.com/item?id=24179043 , Kapton is the final "gold foil" layer in a foil sandwich to insulate almost all spacecraft, inclusive of the LEM. It was used extensively as insulation in almost every Apollo subsystem, including the Command Module, and it became a small tradition to take pieces of the foil with you after splashdown. A final keepsake after a mission gone well. Others adopted the tradition and pilfered more pieces of foil. They were fairly indiscriminate. And spread the fruits widely. You can buy your own from places like here, https://shop.minimuseum.com/products/apollo-11-command-module-foil https://shop.minimuseum.com/products/apollo-11-command-modul... Personally, I would have loved to own a piece of our robotic explorers. Kapton has been used in incredible ways in craft like New Horizons. It's possible to overheat instruments in an object millions of miles away from the sun! https://mattcbergman.com/2015/08/02/new-horizons-thermal-control-system/ https://mattcbergman.com/2015/08/02/new-horizons-thermal-con...