Before humanity first set foot on the lunar surface, the moon was an elusive rock in our night sky. Scientists weren't sure how it formed or what it was made of, and there was even a common misconception that the moon's surface would be fluffy.
"There was real concern that our lunar landers would sink into the surface because the material was so fluffy," Paul Hayne, assistant professor at the Department of Astrophysical and Planetary Sciences at the University of Colorado, told Space.com.
This was not merely an irrational fear; rather, it was based on observations from Earth that showed the surface of the moon to be quite fluffy.
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"What they didn't know was that layer of fluffy material was not very deep," Hayne added. "So, fortunately, nobody sunk into the moon, and that misconception was put to bed."
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A fluffy moon? No.
It may be obvious to us today that the moon wouldn't have swallowed the lunar lander whole, but before Apollo 11, the moon hid many secrets in its shadows.
"We actually didn't know a whole lot about the moon before Apollo," Sarah Noble, the Apollo next-generation sample analysis program executive at NASA headquarters in Washington, told Space.com. "So, in some ways, we wanted to learn everything."
Scientists were (and still are) curious about how the moon came to be in the first place.
Before Apollo, there were different theories regarding the formation of the moon, including that the moon had already formed before it got caught in Earth's gravitational field, or that the moon and Earth formed at the same time about 4.5 billion years ago. But the theory that a number of scientists were leaning toward was that it had been formed as a result of a giant impact between Earth and another planetary body the size of Mars.
What made the moon?
One of the main samples that Apollo astronauts were looking to collect was a piece of the original crust of the moon, which scientists could use to test their hypotheses about how the moon was formed, Noble said.
"The astronauts were all so well trained that it was believed they had the equivalent of a master's degree in geology by the time they got there," Noble said. "It showed in their ability to pick out the right samples."
The samples collected from the moon had the same isotopic formation as geological samples from Earth, therefore supporting the impact theory. Although it is the leading moon formation theory today, some are still arguing in favor of other ways the moon could have come to be.
The testing of these samples also showed that there is water on the moon, even though scientists had believed that it was completely dry.
Another thing that astronomers wondered about when looking at the moon was the origin of the craters on its surface.
"The first thing you notice when you look at the moon through a telescope was the craters," Hayne said. "There was still debate about the origins of the craters before the Apollo missions."
At the time, there were two competing theories. Scientists believed that either the craters had been formed by volcanic activity on the moon, or that the craters were a result of impacts between the moon and other bodies in space.
However, observing the shapes of the craters and analyzing the samples brought back by Apollo supported the theory that the craters were formed by collisions.
The Apollo missions also provided insight into the violent space environment, according to Hayne.
"What we found on the moon was that the entire surface of the moon had been impacted by meteorites, and because it doesn't have rivers, those impacts had not been erased over time," he said. "From looking at the moon's impact history, we know that the Earth has also been hit by meteors."
A lunar time capsule
The difference between the impacts left over on the moon's surface and that of Earth's is that Earth's flowing rivers or growing greenery have erased the marks left behind, while they remained visible on the moon.
Knowing that impacts were an occurrence in space has allowed us to prepare for possible future asteroid collisions here on Earth, Hayne added.
In addition to the moon, the Apollo missions provided more insights regarding our whole solar system.
Before Apollo, scientists had made observations of other planets, but there was no way to determine the ages of those bodies.
However, by testing the samples of moon rocks and lunar soil collected from the Apollo missions and analyzing their composition and structure, researchers estimated the age of the moon and used that knowledge to help figure out the ages of other objects in the solar system.
"The entire chronology of the solar system events is now connected to the ages of the samples collected by Apollo," Hayne said.
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Passant Rabie is an award-winning journalist from Cairo, Egypt. Rabie moved to New York to pursue a master's degree in science journalism at New York University. She developed a strong passion for all things space, and guiding readers through the mysteries of the local universe. Rabie covers ongoing missions to distant planets and beyond, and breaks down recent discoveries in the world of astrophysics and the latest in ongoing space news. Prior to moving to New York, she spent years writing for independent media outlets across the Middle East and aims to produce accurate coverage of science stories within a regional context.