The Two Faces of the Moon
The far side looks *nothing* like the side that faces us. After 55 years, we may finally know why.
“When you’re finally up at the moon looking back on earth, all those differences and nationalistic traits are pretty well going to blend, and you’re going to get a concept that maybe this really is one world and why the hell can’t we learn to live together like decent people.” -Frank Borman, Apollo 8
If you’ve ever looked up at the brightest object in the night sky, you’ve probably noticed how different some parts of it appear to be from others. And if you’ve ever taken a look at it through a telescope, especially if it’s not in its full phase, you’ve very likely noticed some remarkable features on its surface.
In particular, there are two main features about the Moon that you can’t miss:
- That it’s heavily cratered, especially in the lighter-colored areas. Many cratered regions include small craters inside medium-sized craters inside giant craters. And…
- That it has these dark areas known as maria (latin for “seas”), which have relatively few and mostly smaller craters in them. Mostly, these regions are notable for being a significantly different color than the majority of the Moon.
The same side of the Moon always faces us, but different portions of the lunar hemisphere get illuminated throughout the month, dependent on the relative positions of the Earth, Moon and Sun.
In addition, because the Moon’s orbit is elliptical, moving faster when it’s closest to Earth and slower when it’s farthest away, the face of the Moon that’s visible changes ever-so-slightly, a phenomenon known as lunar libration. Even though this means, over the course of many months, we could see up to a total of 59% of the Moon, it wasn’t until 55 years ago, when the Soviet spacecraft Luna 3 swung around to the far side of the Moon, that we got our first pictures…