Credit: NASA/JPL-Caltech/Space Science Institute Over time, this debris coalesced to form the moon.This unprocessed image of Saturn’s moon Atlas was taken on April 12, 2017, by NASA’s Cassini spacecraft. Debris from the impact was launched into orbit and formed a ring around the young Earth. Fortunately, the impact between Theia and Earth happened at just the right angle and speed that the Earth absorbed the smaller planet. Such an impact would be unlike anything humanity has witnessed, and there was a risk that the impact could have completely destroyed the Earth. Theia impacted the young Earth 4.5 billion years ago. This planet, called Theia, was approximately the same size as Mars. During the Earth’s formation, another planet formed nearby. Every planet in our solar system experienced one or more planetary impacts, and the Earth is no exception. The early solar system was chaotic, and impacts between planets were common. Although the solar system contains eight planets today, in the early days of the solar system, as many as a hundred planets likely formed around the sun. Shortly after the formation of the sun, a large disk of stellar material formed around the sun called a protoplanetary disk. Planetary Impact Rendition of two planets colliding. The fact that the moon’s composition was similar yet not identical to the Earth suggested something else caused its formation. If it simply budded off the Earth, its composition would be 100% identical to the Earth.
If the moon were a captured object, it would not have a composition so similar to the Earth. When scientists discovered that the moon was similar in composition to the Earth, it largely disproved these ideas. Another explanation was that the young Earth was spinning so fast that part of it separated from the Earth, similar to how a bacterium will split in half. Some proposed that the moon formed elsewhere in the solar system and was captured by the Earth’s gravity. Relative to the size of the Earth, the moon is a fairly large object, and it is unlikely that it formed simply from debris that fell into Earth orbit. For decades, scientists had tried to explain how the moon could have formed. The age of the moon is also not much younger than the age of the Earth, around 4.5 billion years old. The moon is remarkably similar in composition to the Earth, yet it is not exactly identical.
Lunar samples revealed something rather interesting.
Apollo astronauts brought back multiple samples of the lunar surface, allowing scientists on Earth to determine the age and composition of the moon. Not only was this a significant technological achievement, it also gave scientists an unprecedented opportunity to study the surface of the moon. From 1969 to 1972, NASA accomplished six successful landings on the lunar surface during the Apollo Program. Humanity first stepped foot on the moon in 1969 with Apollo 11. Composition Of The Moon Image of the Earth taken during the Apollo 8 mission in 1968.