It took less than a week to NASA Administrator Bill Nelson’s blunder to go on social media.
More than an hour after the start of a budget hearing for the United States space agency, a congressman asked Nelson why China was sending a spacecraft to the “back” of the Moon.
“They’re going to have a lander on the far side of the Moon, which is the side that’s always in darkness,” Nelson, a former senator and astronaut, said at a news conference. the hearing of April 17. “We have no plans to go.”
He then told lawmakers: “We don’t know what’s on the back of the moon.”
This was wrong on two counts: the dark side of the Moon is not dark, contrary to popular belief, and it is not completely unknown to American scientists either.
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What is the hidden side of the Moon?
The far side is the hemisphere of the Moon opposite the Earth. Because people never see it, this part was once nicknamed “the dark side.” This inappropriate and confusing term has led many people to wrongly assume that the dark side is shrouded in darkness. In reality, it receives as much light as the visible side.
Perhaps the actual “dark” location on the moon is where NASA plans to send Artemis astronauts in the years to come: the south polar region, where scientists believe the frozen water is buried. The south is pockmarked with icy craters shrouded in shadow.
The far side is the hemisphere of the Moon opposite the Earth.
Credit: NASA/NOAA
Why do we only see one side of the Moon?
It takes about a month for the moon, about 250,000 miles, to orbit the Earth. It also takes the same amount of time for the Moon to complete one complete rotation on its axis. This coincidence is the reason why Earthlings always see the same lunar side.
Before space exploration, many thought the dark side was a frozen, foreboding region, a myth perpetuated by Pink Floyd’s trippy 1973 album “Dark Side of the Moon.”
Indeed the far side remained an enigma to humans, but only until October 1959. That’s when the Soviet space program rotated the Luna 3 probe around the Moon. The spacecraft sent back several grainy images that revealed a curiously different surface than that of the familiar near side.
Crushable speed of light
About half a century later, NASA launched the Lunar Reconnaissance Orbiter to explore the region from space. Since then, the spacecraft has sent back a lot of data, allowing scientists to map the dark side in detail.
The Soviet space program launched the Luna 3 probe around the Moon in October 1959.
Credit: Luna 3 / Russian Space Agency / NSSDCA
What does the hidden side look like?
What scientists have learned is that the side humans can’t see is very different.
Although the near side has large dark spots that together resemble a face, known as the “man in the moon”, the far side has few of these spots. THE the spots are called Maria, dark areas formed when meteoroids hit the moon, causing lava to emerge. Not only did the lava make the surface darker, but it also erased previous craters that recorded part of the moon’s geologic history.
The far side, on the other hand, is covered with other craters of different sizes and depths, including the enormous South Pole-Aitken basin.
During the era of NASA and the Soviet Union’s space race, spaceships never landed on the unseen side. This was partly due to how difficult it is. The Moon itself blocks communication between mission controllers on Earth and the far side. But in 2018, China placed a communications relay satellite in space about 40,000 miles beyond the Moon, capable of exchanging signals.
The far side of the Moon receives as much light as the near side.
Credit: NASA / USRA / GSFC visualization
Why is China going to the far side of the Moon?
Back to the April 17 House Appropriations Committee hearing: U.S. Rep. David Trone asked Nelson what made China so interested in the hidden siderather than the South Pole.
“I have no idea,” Nelson said. However, he explained that the United States would go to the south pole of the Moon because that is where NASA suspects water is preserved in dark craters. It is a vital economic resource for future lunar efforts.
But scientists say there is actually much to be gained by studying the dark side, which appears to have more intact traces of earlier histories. cosmic collisions and impacts.
NASA’s Moonkam observing the far side of the Moon.
Credit: NASA/Caltech-JPL/MIT/SRS
On December 8, 2018, China launched the Chang’e-4 mission and became the first nation land on the far side of the moon. It landed at Von Karman Crater, a site located in the South Pole-Aitken Basin.
The basin is a depression likely formed by an ancient asteroid collision so cataclysmic that it excavated part of the lunar mantle – the material between the core and crust – and brought it to the surface. The benefit of going to this location is the opportunity to learn more about the interior composition of the Moon.
What China discovered, according to a published article in the magazine Scientists progress, is that the layer of soil there is much thicker than on the nearest side. It was about 130 feet deep.
If the crust was much thinner on the Earth-facing side, that could explain why lava was able to break through and form the Marian Spots. But it’s unclear why the crustal thickness of one hemisphere would be so radically different from that of the other. China future missions can help answer this question.
Solving such mysteries could not only tell us more about the Moon’s evolution, but also provide deeper insight into the history of the solar system.
