“The planet Earth seemed a long way off in this scene,” says Alan Bean, “because it was—about a quarter of a million miles, in fact. From the Moon, the Earth appeared as a beautiful blue-and-white marble with occasional small orange areas, which were deserts.

“The Moon itself was a foreboding place when viewed from orbit, mostly gray with stark, angular mountains and deep, rough canyons and craters. It was as if nature had pounded it again and again with a big, big hammer.

“In contrast, our Earth was beautiful—all shiny and brig. . .