Parrot Asteroid Tablet

The three little moons (Methone, Pallene, and Anthe) orbit at very similar distances from Saturn, and they have a dynamical relationship. Mimas disturbs the trio of little moons, and causes the orbit of Methone to vary by as much as 20 kilometers (12.4 miles). Mimas causes the orbit of Pallene to vary by a slightly smaller amount--but it has the greatest influence on the orbit of the moon Anthe. 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. Dr. Soderblom calculated the gravity signatures both in and around 1,200 craters that had been excavated by impacting objects on the lunar far side. He then went on to compare the gravity within each crater with the gravity of the surrounding terrain. Dr. Soderblom did this in order to determine whether an impact increased or decreased the local porosity.