Scientists have wondered how is it that Earth is the only planet in our solar system that has a large, single moon? It’s a mystery, especially in light of our knowledge of the other planets in the solar system. Mercury and Venus are moonless, Pluto has a moon nearly as big as itself but Pluto is a dwarf planet, thus its moon is a very small object. Mars has several moons but all of them are small and inconsequential in comparison to Earth’s moon. The other large planets all have many moons among them but these moons are more like dwarfs or Kuiper Belt objects. Some exceptions to this might be Enceladus and Titan but even so, these moons don’t have the influence on these planets that our moon has on the earth. Our large moon is that way for a reason. If it was too small it wouldn’t have the necessary influence to help life thrive one earth.
So, Earth’s moon is special. But how did it come to be? There are three different theories that scientists use to explain our large single moon: Capture Theory, Accretion Theory and Impact Theory.
The Capture Theory posits that the moon formed outside of the solar system and at some point happened to be moving through this system, moved too close to the earth’s gravitational field and was captured by the earth. Most scientists today think that this is unlikely because of the moon’s size in relation to the earth. It’s too big to be captured by the earth in such a manner. It simply would’ve kept going on it’s previous trajectory. Also, it is likely that the composition of the materials on the moon would be very different from the composition of minerals and rock on Earth if it came from outside the solar system. There are too many similarities in rock composition between the two bodies for the moon to have been formed outside of the solar system.
Accretion Theory says that the moon and the earth were formed around the same time and that the moon was directly formed from the earth. Matter broke off and formed it’s own body as the earth was forming and spinning and this matter formed our moon. The problem with this theory is that the composition of the materials on the moon, while sharing similarities, are too different from the elements on Earth for it to actually come from the earth itself. Most scientists think that it must have formed separately from the earth.
Impact Theory (Orpheus Theory). Impact Theory is the most probable and the most exciting as well. Impact Theory states that the moon formed from the impact and the destruction from a planet that used to be part of the solar system. This now missing planet was roughly around around the same size as Mars and its orbit was the area between Earth’s orbit and Mars’s orbit. This planet is named Orpheus. At some point Orpheus and the earth collide. Orpheus is completely broken apart while Earth, while devastated, eventually re-forms again. Earth captures massive amounts of debris from this cataclysmic event. The captured debris is thought to have formed as rings around Earth by some. But if the debris formed rings then eventually these rings would disappear. Why? They would not form a moon but because they would probably be within Earth’s Rosch Radius and eventually they would’ve been completely dissolved into the Earth. So most likely what happened is that the debris from the catastrophe that didn’t fall to Earth coalesced within Earth’s gravitational field and became our moon.
Our moon is important for life on Earth to be maintained. It stabilizes the earth on its axis which keeps the climate stable and regulates climate changes. If we didn’t have a large moon the earth would wobble radically and constantly on its axis like Mars. The climate would go through extreme changes and the earth would tip over from pole to pole. If we didn’t have a moon the days would be much longer and temperatures would become extreme. It controls the tides of the oceans as well. If we didn’t have a large moon we would see tsunami tidal waves all of the time and the earth’s oceans would rule the planet as they did in the beginning. There would be no land based life and very little land above water. It is said that the full moon affects the minds and moods of people. But that’s another article!
So our moon is important and very special. In fact, many things about our Earth make the earth itself very special. The large single moon we have maintains life here and controls the oceans so that we might live on land. It stabilizes the earth’s axis so that life can flourish on a temperate planet. It’s influence helps to nurture life on Earth and allow it to thrive in a positive environment. Our moon is special and unique, indeed!