After beginning its journey to the moon after a dramatic trans-lunar injection, the four-strong crew of the Orion spacecraft sent back some spectacular images of Earth.

A half century after NASA's Apollo 17 lunar module lifted off the moon's northeastern near side quadrant, planetary scientists still don't completely understand when or how our moon first formed. They do agree that it involved a major impactor—an object dubbed Theia by lunar scientists—that likely struck Earth some 4.

What would Earth be like if there were no Moon? Peter Allen RhodesNorth Bellmore, New York Without the Moon, Earth's geology, biology, and climate - as well as human philosophy - would be different in many significant ways.