When the Earth Had Two Moons

This expert guide to plant formation and the origins of life “makes the solar system an even weirder and more wonderful place than it seemed before” (Wall Street Journal).

In 1959, the Soviet probe Luna 3 revealed an astonishing truth: the far side of the moon is an enormous mountainous expanse, completely different from the vast lava-plains on the side facing Earth. But why would the two side of t...