Our Moon. It lights up our nights, governs our tides and has inspired millions - perhaps billions -– of people throughout history to contemplate its nature, its influence on our lives (if any) and, of course, where it may have come from.
The currently accepted theory is that over four and a half billion years ago, our newly formed planet was hit by a Mars-sized body, a catastrophic collision that flung molten bits of Earth's mantle into space and created a ring of debris.
This ring gradually coalesced into the moon, which cooled and moved further and further away from Earth into its current position. This theory is widely accepted, and research on the composition of lunar samples seems to coordinate with an Earthly origin of the moon. But one thing never quite lined up perfectly with the whole scenario: the moon's far side.
The lunar far side looks very different from the face we see. It is much more heavily cratered, for one thing, in fact featuring one of the largest impact basins in our solar system. It lacks the features that create the "man-in-the-moon" patterns so familiar to us and while the near side is relatively flat, the far side is much more mountainous.