It took less than a week NASA Administrator Bill Nelson's social media gif of making it.

More than an hour into the budget hearing for America the location agency, a congressman asked Nelson why China was sending spacecraft to the “back side” of the moon.

“They're going to have a lander on the far side of the moon, which is the side that's always dark,” said Nelson, a former senator and astronaut. April 17 hearing. “We're not planning to go there.”

“We don't know what's on the back side of the moon,” he told the lawmaker.

In two respects, it was wrong: Despite popular belief, the so-called far dark side of the Moon is not, nor is it completely unknown to American scientists.

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What is the dark side of the moon?

The far side is the hemisphere of the Moon that is away from Earth. Because people never see it, this part was once called the “dark side.” The vague misnomer has led many to wrongly assume that the era is shrouded in darkness. In fact, it receives just as much light from the near side.

Perhaps there is an actual “dark” spot on the Moon. Where NASA plans to send Artemis astronauts. In the coming years: the Antarctic region, where scientists believe water ice is buried. The south is marked by pockets of cool craters shrouded in shadow.

Why do we see only one side of the moon?

It takes about a month for the moon, Some 250,000 miles away, in Earth's orbit. It takes the same amount of time for the moon to complete one rotation on its axis. It is this coincidence that people on earth always look at the same moon.

Before space exploration, many speculated that the far side was a frozen and inhospitable region, a myth established by Pink Floyd's trippy “Dark Side of the Moon” album in 1973.

No doubt On the far side It remained a mystery to humans, but only until October 1959. That's when the Soviet space program launched the Luna 3 probe around the moon. The spacecraft returned several grainy images that revealed Amazingly different levels It's closer to the familiar than it is.

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Almost half a century later, NASA launched Lunar Reconnaissance Orbiter To explore the region from space. Since then, the spacecraft has sent home a wealth of data, allowing scientists to map the far reaches in detail.

What does the far side look like?

What scientists have learned is that what humans cannot see is completely different.

While there are large dark spots on the near side that together resemble a face, known as the “Man in the Moon,” there are few spots on the far side. gave The spots are called maria., the dark regions are formed when meteoroids hit the Moon, which ejects lava. The lava not only darkened the surface, it also erased previous craters that recorded some of the moon's geologic history.

On the other hand, the far side is covered by more craters of different sizes and depths, including the huge South Pole-Atkin Basin.

During the era of NASA and the Soviet space race, spacecraft never landed in space. Part of it was because of him. That's how hard it is. The moon itself blocks communications between Earth and distant mission controllers. But in 2018, China launched a communications relay satellite about 40,000 miles from the moon that could exchange signals.

Why is China moving towards the moon phase?

Back to that House Appropriations Committee hearing on April 17: U.S. Rep. David Troon asked Nelson what made China is very interested in remote areas.Instead of the South Pole.

“I have no idea,” Nelson said. However, he explained that the US was going to the South Pole of the Moon because that's where it was. NASA suspects water. Preserved in dark pits. It is an important economic resource for Future lunar endeavors

But scientists say there's actually a lot more to be learned from studying the far-back, which appears to be a much older record. Cosmic Clash and effects.

On December 8, 2018, China launched the Chang'e-4 mission and became the first country Landing on the far side of the moon. It descended over the Van Kerman Crater, located within the South Pole-Aitken Basin.

The basin is a depression likely created by an ancient asteroid impact so destructive that it excavated some of the moon's mantle—the material between the core and crust—and brought it to the surface. The advantage of visiting this location is the ability to learn more about the internal structure of the Moon.

According to China, what was found? A paper was published In the journal Advances in science, is that the soil layer is thicker on the near side. It was about 130 feet deep.

If the crust was very thin on the Earth-facing side, this could explain why the lava was able to break off and form the maria spots. But why the layers of one hemisphere would differ so much in thickness from another is not clear. Of China Future missions It may help to answer this question.

Solving such mysteries can not only tell us more about the evolution of the Moon, but also provide more insight into the history of the Solar System.