It took lower than per week for NASA Administrator Invoice Nelson’s gaffe to make it to social media.
Over an hour right into a funds listening to for the U.S. area company, a congressman requested Nelson why China is sending spacecraft to the “bottom” of the moon.
“They will have a lander on the far facet of the moon, which is the facet that is all the time in darkish,” mentioned Nelson, a former senator and astronaut, throughout the April 17 listening to. “We’re not planning to go there.”
He proceeded to inform the lawmaker that “We do not know what’s on the bottom of the moon.”
On two counts, that was unfaithful: The so-called far facet of the moon shouldn’t be darkish, regardless of well-liked perception, neither is it utterly unknown to American scientists.
What’s the darkish facet of the moon?
The far facet is the hemisphere of the moon dealing with away from Earth. As a result of folks by no means see it, that portion was as soon as dubbed “the darkish facet.” The complicated misnomer has led many to incorrectly assume the far facet is shrouded in darkness. In actuality, it receives simply as a lot gentle because the close to facet.
Maybe the precise “darkish” location on the moon is the place NASA plans to ship Artemis astronauts within the coming years: the polar south area, the place scientists consider ice water is buried. The south is pockmarked with frigid craters cloaked in shadow.
The far facet is the hemisphere of the moon dealing with away from Earth.
Credit score: NASA / NOAA
Why can we solely see one facet of the moon?
It takes a couple of month for the moon, some 250,000 miles away, to orbit Earth. It additionally takes the identical period of time for the moon to make one full rotation on its axis. This coincidence is why Earthlings all the time see the identical lunar facet.
Previous to area exploration, many speculated the far facet was a frozen and ominous area, a fable perpetuated by Pink Floyd’s trippy “Darkish Aspect of the Moon” album in 1973.
Certainly the far facet remained an enigma to people, however solely till October 1959. That is when the Soviet area program swung the Luna 3 probe across the moon. The spacecraft returned a number of grainy pictures that exposed a curiously totally different floor than that on the acquainted close to facet.
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A couple of half-century later, NASA launched the Lunar Reconnaissance Orbiter to discover the area from area. Since then, the spacecraft has despatched residence a great deal of information, permitting scientists to map the far facet intimately.
The Soviet area program swung the Luna 3 probe across the moon in October 1959.
Credit score: Luna 3 / Russian Area Company / NSSDCA
What does the far facet appear to be?
What scientists have discovered is that the facet people cannot see is vastly totally different.
Although the close to facet has giant darkish patches that collectively resemble a face, generally known as the “man within the moon,” the far facet has few of those spots. The spots are referred to as maria, darkish areas fashioned when meteoroids slammed into the moon, inflicting lava to emerge. Not solely did the lava make the floor darker, however it erased earlier craters that recorded a few of the moon’s geological historical past.
The far facet, alternatively, is blanketed in additional craters of varied sizes and depths, together with the large South Pole-Aitken basin.
In the course of the NASA and Soviet area race period, spacecraft by no means landed on the unseen facet. A part of that was due to how tough it’s. The moon itself blocks communication between mission controllers on Earth and the far facet. However in 2018, China put a communication relay satellite tv for pc in area about 40,000 miles past the moon that might change the indicators.
The far facet of the moon receives simply as a lot gentle because the close to facet.
Credit score: NASA / USRA / GSFC visualization
Why is China going to the far facet of the moon?
Getting again to that Home Appropriations Committee listening to on April 17: U.S. Rep. David Trone requested Nelson what made China so within the far facet, reasonably than the south pole.
“I do not know,” Nelson mentioned. He did, nevertheless, clarify that the U.S. goes to the moon’s south pole as a result of that is the place NASA suspects water is preserved in darkish craters. It is a important financial useful resource for future lunar endeavors.
However scientists say there’s truly so much that may very well be gained from finding out the far facet, which appears to have a extra pristine file of earlier cosmic collisions and impacts.
NASA’s Moonkam viewing the far facet of the moon.
Credit score: NASA / Caltech-JPL / MIT / SRS
On Dec. 8, 2018, China launched the Chang’e-4 mission and have become the primary nation to land on the reverse facet of the moon. It touched down on the Von Karman crater, a web site inside the South Pole-Aitken basin.
The basin is a despair in all probability fashioned by an historic asteroid collision so cataclysmic that it excavated a few of the lunar mantle — materials between the core and the crust — and introduced it to the floor. The benefit of going to this location is the potential to study extra concerning the inside composition of the moon.
What China discovered, based on a paper revealed within the journal Science Advances, is that the layer of soil there may be a lot thicker than on the close to facet. It was about 130 ft deep.
If the crust have been so much thinner on the facet dealing with Earth, that may clarify why lava was capable of break via and type the maria spots. However why one hemisphere’s crust can be so drastically totally different in thickness from the opposite is unclear. China’s future missions might assist reply that query.
Fixing such mysteries couldn’t solely inform us extra concerning the moon’s evolution, however present additional perception into the historical past of the photo voltaic system.
