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 the moon be so different? And what might this tell us about our own place in the universe? As it turns out, quite a lot.


Fourteen billion years ago, the universe exploded into being, creating galaxies and stars. Planets formed out of the leftover dust and gas that coalesced into larger and larger bodies orbiting around each star. In a sort of heavenly survival of the fittest, planetary bodies smashed into each other until solar systems emerged. Curiously, instead of being relatively similar in terms of composition, the planets in our solar system, and the comets, asteroids, satellites and rings, are bewitchingly distinct. So, too, the halves of our moon.


In When the Earth Had Two Moons, esteemed planetary geologist Erik Asphaug takes us on an exhilarating tour through the farthest reaches of time and our galaxy. Beautifully written and provocatively argued, When the Earth Had Two Moons is not only a revealing look at outer space, but a profound inquiry into the nature of life here.