Answer: Australite

One of the earliest concerns of NASA’s manned space programs was not as much how to get Astronauts safely into space, but how to get them safely back to Earth. Getting someone out of the atmosphere isn’t nearly as daunting of a task as getting them back through the re-entry process unharmed.

In order to help in the modeling and shaping of their Apollo-era re-entry modules, NASA turned to a naturally occurring object that had already been through the re-entry process: Australite. Australite is a form of tekkite–a type of glass formed when a terrestrial impact, such as a comet hitting Earth, ejects rocks high into the upper atmosphere.

Unlike most tekkites, Austalites took on a very aerodynamic and streamlined form during re-entry. Scientists at NASA studied the button-like shape of Australites and the way the glass had molten and cooled within. Armed with that knowledge the designed a significantly larger but similarly shaped base for the Apollo re-entry modules.