The planet Mercury as seen from the MESSENGER spacecraft, for MErcury Surface, Space Environment, GEochemistry, and Ranging. The mission has uncovered a wealth of new information about the nearest planet to the sun. Its core is relatively huge, for one thing — almost 85 percent of the planet's radius. By contrast, Earth's core is about half its radius.
Five amazing, clean technologies that will set us free, in this month's energy-focused issue. Also: how to build a better bomb detector, the robotic toys that are raising your children, a human catapult, the world's smallest arcade, and much more.