As the moon orbits the Earth, we only ever see the one side. This is because the moon is tidally locked -- a single rotation of its axis takes the same amount of time as a single orbit around the Earth, so that the same side is always facing the Earth.
This means that the far side of the moon is a mystery to most of us. We're familiar with the smudges of the Man in the Moon (or the Moon Rabbit), but who knows what pareidoliac delights lurk on the moon's other face?
As it turns out, NASA's Lunar Reconnaissance Orbiter, a robotic spacecraft orbiting -- and mapping -- the moon since June 2009 does.
As the moon goes through its phases, we see it darken and lighten. Those phases are the opposite of what the far side of the moon experiences: when we have a full moon, the far side is new; when we have a new moon, the far side is full. This means that the LRO can observe the far side of the moon in pretty good detail when it is illuminated by the sun.
In the years since it has launched, the LRO has sent back hundreds of terabytes of data about the moon's far side. What it has found is that the far side of the moon is quite different from the side we see.
"It lacks the large dark spots, called maria, that make up the familiar Man in the Moon on the near side," NASA wrote. "Instead, craters of all sizes crowd together over the entire far side. The far side is also home to one of the largest and oldest impact features in the solar system, the South Pole-Aitken basin."
Check it out: the moon as you have (probably) never seen her before: