Earth’s core could contain helium from the early solar system. The noble gas tucks into gaps in iron crystals under high pressure and temperature.

3D printers will make the tools, structures and habitats space pioneers need to survive in a hostile alien environment. They will enable long-term human presence on the Moon and Mars.

Steel and aluminum are ubiquitous in Americans' lives. Here’s a look at some of the industries and products that rely on them.