NASA Astronaut Glove

There was a time when Earth had no Moon. About 4.5 billion years ago, when our ancient Solar System was still forming, the dark night sky above our primordial planet was moonless. At this time, the Earth was about 60 percent formed, although it did have a differentiated crust, mantle, and core. This was a very chaotic and violent era in our Solar System's past, with planets first forming out of blobs of primordial dust, gas, and rock. During this era, frequently likened to a "cosmic shooting gallery", collisions between the still-forming planets were commonplace. Orbits were not as orderly as they are now. "The near-side of the Moon has been studied for centuries, and yet continues to offer up surprises for scientists with the right tools. We interpret the gravity anomalies discovered by GRAIL as part of the lunar magma plumbing system--the conduits that fed lava to the surface during ancient volcanic eruptions," Dr. Maria Zuber explained in an October 1, 2014 NASA Press Release. Dr. Zuber is from the Massachusetts Institute of Technology (MIT) in Cambridge. Astronomers have known for years that the temperatures of the lunar near-side are higher than those on the far-side. This is because the abundances of the heat- producing elements uranium and thorium are greater on the near-side than on the far-side. In addition, these higher temperatures are a consequence of the fact that most of the volcanic eruptions occurred on the lunar near-side.