What’s Hiding on the Dark Side of the Moon?
Humans have been staring up at the Moon for as long as we’ve been around, wondering
what secrets our sibling in the sky might hold. But for all that time, we’ve only
ever been looking at one side of it, the near side. If the half we CAN see see has proved
itself intriguing and mysterious, wait until you hear about the one we can’t.
This is Unveiled, and today we’re answering the extraordinary question: what’s hiding
on the dark side of the Moon?
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It’s actually incorrect to call the dark side of the Moon “the dark side of the Moon,”
which any astronomer worth their salt will point out. The misnomer has led many folk
to believe that the other side of the Moon is constantly shrouded in darkness, always
facing away from the sun, but that’s just not true. In actuality, the Moon has its own
day and night cycle, and both sides get the same amount of light from the Sun. The “far
side” is only “dark” in the sense of unseen and unknown. The reason the Moon has
a far side and a near side is that it’s tidally locked to the Earth, meaning that
it rotates on its own axis at the same speed that it orbits the Earth, leaving one side
always facing us. Mind you, the far side isn’t quite as elusive as you might think; because
the Moon “wobbles” or oscillates on its axis, a phenomenon called “libration”,
around 18% of the Moon’s far side can be visible to human eyes depending on which phase
it is in.
In a literal sense, what you’d find if you went to the far side of the Moon is a considerably
rougher surface, with more craters and fewer maria. Maria are those large, dark patches
you can see on the Moon’s surface, thought to be remnants of vast magma oceans. It was
once speculated that the Earth “shielded” the near side from meteor impacts, but it’s
now believed that the near side just experienced more volcanic eruptions, creating a smoother
surface. This could be in part because the crust of the far side is colder and thicker.
The craters on the far side were first photographed in 1959, by the Soviet space probe Luna 3
as it orbited the Moon. A year later the Soviets used this data to publish the first official
map of the Moon’s far side. Then, in 1968 humans saw it with their own eyes for the
first time during the Apollo 8 mission, which orbited the Moon and then returned to Earth.
But up until January 2019, every single landing on the Moon was made on the near side, due
to the difficulties in communicating with missions on the far side. The Chinese National
Space Administration changed all that when they launched the Chang’e 4 prove, carrying
the Yutu 2, or Jade Rabbit 2, lunar rover. The aim of sending Yutu 2 was primarily to
study the soil and surface temperatures. It discovered that the far side of the Moon is
even colder than expected, possibly due to the soil composition.
This isn’t the only new discovery about the Moon’s far side, either. In April 2019,
scientists announced the discovery of an enormous mass buried beneath the South Pole-Aitken
crater, based on data from NASA’s Lunar Reconnaissance Orbiter. The crater is the
largest crater we’ve so far discovered in our solar system, and the mysterious mass
is a chunk of metal five times the size of the Island of Hawaii, buried 186 miles beneath
the surface. The researchers have different theories for what it might be. It may be the
asteroid that made the crater in the first place; or it could just be oxides on the Moon
cooling and solidifying.
Part of what makes the Moon’s far side so intriguing is that it’s difficult to communicate
with the far side from Earth. The Apollo 8 astronauts lost contact with mission control
until they emerged from the other side, because the Moon itself blocks radio waves. This makes
a mission to the far side complicated, but China found a way around it by launching a
communication relay satellite, named Queqiao. This satellite orbits the Earth at exactly
the same speed as the Moon, using the Moon’s gravity. It does so in a position that’s
always within sight of Chang’e 4 and the Earth, allowing it to communicate with both.
While this was first suggested in the 1960s, it’s taken this long for anybody to actually
try it – and so far, it works. What this means is that our biggest problem when it
comes to communicating with the far side has, essentially, already been solved.
Of course, certain people have very different ideas about what might be hiding just out
of sight, and conspiracy theories about the Moon’s other face abound. Most recently
there have been theories that the entire Chang’e 4 launch was faked. On the other end of the
spectrum are people who believe Chang’e 4 is real but has a secret purpose: documenting
hidden alien bases on the Moon. The “aliens on the dark side of the Moon” theory has
been popular for a long time. Theorists claim that astronauts who have seen these aliens
have been sworn to secrecy, and that the alien base is codenamed “LUNA”. What the aliens
want from us and what they’re doing there remains unclear.
It does inspire an interesting question, however: would there ever be a good reason for anyone
to build on the far side of the Moon? Well, if at some point in the future humans do decide
to colonize the Solar System, with the Moon as one of their first stops, it could be advantageous
to colonize both sides. The far side might get a bit colder, but as said, it does experience
a day and night cycle and we already have communication over there thanks to Queqiao.
It’s a little harder to get to than the near side, but we wouldn’t have to fly spacecraft
over there to build; we could just build on the near side and then transport things to
the far side by land, using rovers or other lunar vehicles.
Another benefit would be for space launches to other parts of the solar system, since
the Moon has a significantly lower escape velocity than Earth – only 1.5 miles per
second compared to Earth’s 7 miles per second. This would make a far side colony ideal for
missions to Mars or Venus. Even if colony ideas never come to fruition, the far side
of the Moon is an ideal location for a radio telescope free from interference from Earth,
capable of capturing the best data from elsewhere in space.
Though it might just be an enormous expanse of rocks and wasteland, the Moon’s other
face holds lots of opportunities for mankind to build, explore, and discover. And that’s
what’s hiding on the dark side of the Moon.
What do you think? Is there anything we missed? Let us know in the comments, check out these
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