The moon is more than just a celestial body. Its also the source of unanswered questions, speculation, and mystery. One particularly strange mystery involves the vast geographical differences between it’s near side and its far side. Why are these two sides so different from each other?

The Moon: Near Side vs. Far Side

The moon doesn’t rotate. Thus, the near side is always visible from earth while the far side remains shrouded in darkness. But the differences don’t end there. The near side exhibits few mountains and a thin crust. Large rocky plains account for 31.2% of its surface. The far side, in contrast, is marked by mountain ranges measuring over 3,000 feet high and a thick crust. It’s heavily cratered and flat plains account for just 2.5% of its surface.

Secrets of the Moon?

Now, two scholars, planetary scientist Erik Asphaug and his postdoctoral researcher Martin Jutzi, believe they can explain these differences. They recently proposed that the reason the two sides look so different is because they are different. In other words, they think that the moon is, in actuality, two separate celestial bodies!

Using sophisticated computer models, they have shown that it might’ve been formed four billion years ago by a relatively low-speed collision of two separate moons. Their model assumes that the smaller moon smashed into the larger one at about 4,400 miles per hour. At this speed, material from the smaller moon would’ve splattered all over the larger one, creating a thicker crust, a battered surface, and long mountain ranges.

Guerrilla Explorer’s Analysis

The theory doesn’t explain everything. For example, the model assumes that the two moons consisted of the same material. However, the far side of the moon contains heavy concentrations of aluminum, a material that is only found in low quantities on the near side.

Further mineral studies are needed. And fortunately, they’re coming. On September 8, 2011, NASA plans to launch the GRAIL, or Gravity Recovery Interior Laboratory, mission. Two spaceships will fly circular orbits thirty-one miles above the moon’s surface. Using gravity mapping techniques, NASA hopes to determine the moon’s interior structure. That data should help us answer numerous questions about the moon such as, has earth always had just one moon? Or, many centuries ago, did two moons float above our planet?