It was with awe when Apollo 11 landed on the moon and the world watched Neil Armstrong take a step and say, “This is one small step for man, one giant leap for mankind.” The moon has always been mysterious. Many theories about the formation of the moon have been forwarded. The Giant Impact hypothesis was the original theory from which the “Big Splat” theory developed.
A Brief Summary of The Giant Impact Theory
The hypothesis states that Earth was formed from the leftover cloud of dust and gas orbiting the young sun. Some of the bodies did not make it to planetary status and crashed into earth. “Theia,” the Mars size body collided with earth and threw vaporized chunks of the young Earth's crust into space. Gravity bound the particles together to create the moon.
The Splat Theory
The study conducted by scientists at University of California at Santa Clara suggests that there is such a difference between the near side (the side seen every night by Earth) and the far side of the moon. The Grail probes (Gravity Recovery and Interior Laboratory) gives a closer view of the far side of the moon. The far side of the moon is high and mountainous. NASA (National Aeronautics and Space Administration) observed the moon and reported,
“Tidal forces between the moon and the Earth have slowed the moon' rotation so that one side of the moon always faces toward our planet. Though sometimes improperly referred to as the 'dark side of the moon,' it should correctly be referred to as the 'far side of the moon' since it receives just as much sunlight as the side that faces us. The dark side of the moon should refer to whatever hemisphere isn't lit at a given time. Though several spacecraft have imaged the far side of the moon since then, LRO is providing new details about the entire half of the moon that is obscured from Earth. The lunar far side is rougher and has many more craters than the near side, so quite a few of the most fascinating lunar features are located there, including one of the largest known impact craters in the solar system, the South Pole-Aitken Basin. The image highlighted here shows the moon's topography from LRO's LOLA instruments with the highest elevations up above 20,000 feet in red and the lowest areas down below -20,000 feet in blue.” (see NASA picture accompanying this article)
This has led scientists to believe that the “giant impact” created another, smaller body that shared an orbit with the moon. This was the second moon. According to Erik Asphaug, Professor of Earth and planetary sciences at the University of California Santa Cruz, the smaller moon fell back into the moon and coated one side with an extra layer of crust tens of kilometers or miles thick. He wrote, “Our model works well with models of the Moon-forming giant impact, which predict there should be massive debris left in orbit about the Earth, besides the Moon itself. It agrees with what is known about the dynamical stability of such a system, the timing of the cooling of the Moon, and the ages of lunar rocks.”
He and colleague, Martin Jutzi, used computer simulations of the moon and a smaller moon (it is 1/30 of the weight of the moon) and tracked lunar evolution, impact of the two moons, and its distribution of the debris from the moons that compacted and formed the mountainous area of the far side of the moon.
To picture how the collision contributed to the far side of the moon, think of the smaller moon as pancake batter and the earth as the skillet. The pancake batter (the second, smaller moon) hits the skillet (the larger moon) and one side becomes thicker (the far side). That collision is the creation of the mountainous area of the far side of the moon.
Since the dawn of the space age, the far side of the moon has been a puzzle – after questions about the moon formation itself, and will continue to be so. Only future space exploration will help people understand the origin of the moon.