- 18 hours ago
For decades, strange seismic readings made some people wonder whether the Moon could be hollow inside. But newer data points in a different direction: the Moon is not empty, and its interior may be far more complex than expected. What scientists are finding beneath the lunar surface could change how we understand the Moon’s origin, structure, and hidden history.
Category
🎈
FunTranscript
00:00What if our moon was hollow?
00:01Would we be able to hide inside in case some terrible catastrophe destroyed our home planet?
00:07Well, the supporters of the hollow moon theory believe that it's actually a real option.
00:12The hollow moon is a hypothesis claiming that Earth's moon is either completely hollow or has quite a lot of
00:19place inside.
00:20The thing is, the moon is less dense than Earth, and it seems to support the idea of its hollowness.
00:27But according to science, the reason is the fact that Earth's upper mantle and crust are less dense than the
00:34heavy iron core of our planet.
00:36Then, there's also the claim that the moon rings like a bell.
00:41For almost a decade, between 1969 and 1977, seismometers installed on the moon by the Apollo missions kept recording moonquakes.
00:51The moon was reported to be ringing like a bell during such quakes, especially shallow ones.
00:57On the 20th of November, 1969, Apollo 12 deliberately crashed the ascent stage of its lunar module into the surface
01:06of our natural satellite.
01:08According to NASA, after that, the ringing continued for almost an hour.
01:13This made some people argue that the moon must be hollow like a bell.
01:18Later, lunar seismology researched those shallow moonquakes and showed that they acted differently than quakes on our planet,
01:25mostly due to differences in type, texture, and density of the lunar and Earth's rock layers.
01:31The speed of sound waves in solids is determined by the medium's compressibility and density.
01:37No one has ever found any evidence of a large, empty space inside the moon.
01:42And still, in 1970, Michael Vassin and Alexander Cherbakov suggested a hypothesis that the moon could be a spaceship designed
01:52by mysterious extraterrestrial beings.
01:54In 1965, writer Isaac Asimov made an observation that added fuel to the fire of conspiracy theories.
02:02He marveled at the sheer astronomical accident that the moon fit so snugly over the sun during total eclipses.
02:09The sun's greater distance makes up for the incomparably larger size of the star.
02:15As a result, it seems to us that the moon and the sun are the same size.
02:20The author added that there was no astronomical reason why the sun and the moon should fit so well.
02:25So since the 1970s, conspiracy theorists have been quoting Asimov's words about solar eclipses as evidence of the artificial origin
02:34of the moon.
02:36Mainstream astronomers disagree with such an interpretation, saying that the angular diameters of the moon and the sun don't perfectly
02:43match during eclipses.
02:44They vary by several percent over time.
02:47Many other pieces of evidence confirm that the moon is a solid body that formed after a planetoid crashed into
02:54Earth.
02:54In the past, scientists thought that the moon appeared after our rapidly spinning planet got rid of a good chunk
03:01of its mass.
03:02This idea was suggested in 1879 by George Darwin, the son of the very Charles Darwin, the famous biologist.
03:10This theory remained popular until the Apollo missions.
03:14Then, in 1925, Austrian geologist Otto Ampferer offered another idea that Earth and the moon could have formed together from
03:22a primordial accretion disk,
03:24a rotating disk of dense gas and dust surrounding a young, newly formed star, and used to be a double
03:33system.
03:33The third theory stated that the moon could have once been a planetoid caught by the gravity of our planet.
03:40The modern explanation usually involves the giant impact hypothesis.
03:45According to it, a Mars-sized space body hit Earth and created a debris ring around our planet.
03:51In the end, this ring gathered into a single natural satellite, our moon.
03:57But getting back to the hollow moon theory, at the moment, there's no scientific evidence to support this hypothesis.
04:05Seismic observations and other data indicate that the moon has a solid interior with several layers,
04:11a thin crust, quite extensive mantle, and a dense core.
04:16These days, the idea of the hollow moon is considered to be a conspiracy theory.
04:22Okay, I officially give up on the hope that the moon is made of cheese, after all.
04:26Wow, not even Gouda.
04:28The shiny lunar ball, or a curved banana, or half of a coin, depending on what phase it's in,
04:34has different layers inside, just like Earth.
04:37One of these layers is called the inner core.
04:40About 20 years ago, scientists were observing how the moon rotates.
04:44Using that data, they concluded that it had a fluid outer core.
04:48But the inner core was hard to study, so they didn't know if it was solid like a rock,
04:53or molten like a hot liquid.
04:55But things are clearer now.
04:58Astronomers have collected data from different missions, including the Apollo missions,
05:02where astronauts went to the moon and gathered information themselves.
05:05Plus, they've used a special technique called seismic data.
05:09This method is all about studying how sound waves move through things.
05:14Take earthquakes on our planet as an example.
05:16When an earthquake happens, it creates waves that travel through the ground.
05:21Scientists can detect and analyze these waves to learn more about Earth's interior.
05:25The same idea can apply to other objects in our solar system,
05:29or planets, or, in this case, the moon.
05:32When quakes, or moon quakes, happen, they generate sound waves.
05:36And by carefully listening to and studying these waves,
05:40scientists can create a detailed map of what's inside the object.
05:44They can figure out things like different layers, what they're made of, and how they're arranged.
05:49To check the moon's deep interior, scientists also use something called laser ranging.
05:55This method measures the distance between the surface of the Earth and the moon very precisely.
06:01And ta-da!
06:02Our natural satellite's inner core is a dense, solid ball made of iron, just like Earth's.
06:09It's about 310 miles wide, which is nearly 15% the size of the entire moon.
06:14Researchers also have stumbled upon evidence that supports the theory that the layer between the moon's surface and its core,
06:21called the mantle, has been moving around as the moon evolved over time.
06:26This movement is something we call lunar mantle overturn,
06:30and it could explain why we find elements rich in iron on the lunar surface.
06:35Mantle material ends up being carried upward, and the volcanic rock remains in the moon's crust.
06:42Some of the materials in this rock were too dense, like me,
06:46so they just sank back through the lighter crust material all the way to the core mantle boundary.
06:52It's like a cycle where the moon's mantle material goes up during volcanic activity,
06:58carries iron-rich elements to the surface, and then sinks back down.
07:03There's another mystery scientists have been trying to solve.
07:05What caused the moon's magnetic field to weaken and nearly disappear over time?
07:11It seems that now that we know about the iron core and the global mantle overturn,
07:16we might get some more answers about the moon's magnetic field.
07:20Knowing what the inner core is like can help us better understand the moon's history,
07:24as well as the history of our entire solar system.
07:28Now, one of the theories that's widely accepted about the origin of the moon
07:32says there was a massive collision between Earth in its early stages
07:36and another mysterious object in our solar system.
07:39It's called the Large Impact Theory, and this collision was so strong,
07:43it ripped off a big chunk of the primitive molten Earth.
07:48I mean, not so big compared to what's left.
07:50If you put a U.S. nickel next to a green pea,
07:53you get a good idea of how big our planet is compared to the moon.
07:56Now, this chunk was set into orbit around our planet.
07:59And this might have happened about 95 million years after our solar system formed.
08:06The object that collided with Earth could have been about 10% the mass of our home planet
08:11and roughly the size of Mars.
08:13Well, it makes sense.
08:15Earth and the moon do have similar compositions, after all.
08:19Of course, there are other ideas about how the moon formed.
08:22One says that the gravitational force of our planet captured it.
08:28This means that the moon was just an object innocently passing by
08:32when suddenly it got attracted and pulled into Earth's orbit.
08:35There's even a hypothesis that Earth stole the moon from Venus.
08:40In that case, the moon shouldn't complain.
08:42I guess the view is way better here.
08:44So yeah, the moon and Earth are similar when it comes to rocks and some minerals.
08:49But the moon doesn't have the same atmosphere as our planet.
08:53Its atmosphere is thin and consists of some weird gases that include potassium and sodium,
08:58which is not something you can find in the atmosphere of Mars, Venus, or Earth.
09:03And the rocks on the moon don't contain water.
09:05But that doesn't mean there's no water at all up there.
09:09A long time ago, in the 17th century, astronomers saw large, dark spots on the moon's surface.
09:16One of these astronomers thought these spots looked like oceans.
09:19And he called them maria, which means seas in Latin.
09:23Other astronomers also made maps of the moon,
09:26and they used the term maria to describe these dark spots.
09:29For example, Mare Tranquillitatis translates to Sea of Tranquility,
09:34where Apollo 11 made its touchdown.
09:36But it seems those dark spots are not actually oceans.
09:40They are plains made of hardened lava that erupted long ago.
09:45These volcanic eruptions left behind smooth, flat areas called basalt plains.
09:51In the late 1800s, one sky watcher studied the moon and found it didn't have an atmosphere.
09:57Without an atmosphere, there are no clouds and no air to keep water from evaporating.
10:03So scientists thought that any water on the moon would just disappear right away.
10:08They believed the moon was totally dry.
10:10But then, in 1961, one physicist had a different idea.
10:16He pointed out there could be water on the moon in special areas called permanently shadowed regions.
10:22These are spots on the moon where the sun doesn't shine, so they stay dark all the time.
10:28Water ice could exist in these dark areas because they're extremely cold and the ice wouldn't evaporate.
10:35But when astronauts from the Apollo missions went to the moon,
10:38they brought back soil samples, and scientists found no signs of water in them.
10:43So, everyone went back to thinking that the moon was completely dry.
10:48In the 90s, NASA focused on these shadowed craters and found high concentrations of hydrogen,
10:54which meant there could be ice at the moon's poles.
10:57They still weren't certain, so they kept digging and, after a while,
11:01found hydrogen trapped inside tiny beads of volcanic glass.
11:06Since there are no active volcanoes on the moon today,
11:09which means water probably was present on the moon when these volcanoes erupted long ago.
11:15Plus, there could be way more water back in the early days of our moon.
11:20In 2020, NASA's SOFIA mission showed us what we'd been looking for for a really long time.
11:26There is water on the moon, after all.
11:29It turns out the water is hidden within the grains of lunar dust
11:32or sticking to the surface in the sunlit areas of the moon.
11:36So, there are no oceans like we have on Earth, but at least there's something.
11:41The question remains, how did water even get there?
11:45It seems the moon had a chaotic history back at the time when it was forming,
11:49as probably most of the planets and moons in our solar system.
11:53So, there is some evidence that water came there from comets hitting its surface back in the old days.
11:59Or maybe even keeps on coming from those that are slamming into the moon right now.
12:05We're talking about a chaotic situation, where icy micrometeorites collide with the moon's surface,
12:11and dust then makes an even bigger mess when interacting with the solar wind.
12:16But we're waiting to find out more about this.
12:19Because, as we all know,
12:21when you mention water, you also inevitably talk about life.
12:25That's why we want to know more, for instance,
12:28about all that ice hidden in polar craters on the moon.
12:32Maybe it can teach us more about how life developed on Earth.
12:36Maybe comets brought all the necessary elements here.
12:39Then, what if there are some of those elements stuck in the ice on the moon, too?
12:44Hmm.
12:51China's U-2-2 is a robotic mission to the dark side of the moon,
12:55launched on December 7, 2018.
12:58On January 3, 2019,
13:01it completes the first ever soft landing on the lunar far side.
13:05It lands in the Von Karman crater,
13:07not far from the moon's south pole.
13:09Scientists are interested in this area.
13:11Cold, permanently shadowed craters at the poles contain water ice.
13:16These ice patches are uneven and are likely to be ancient.
13:20In the south, most of the water ice is concentrated in craters.
13:24And at the north pole, it's spread more sparsely.
13:27In any case, this ice can be used
13:30once a long-term, manned mission lands on the moon.
13:34Anyway, several days after U-2-2 lands,
13:37it closes down its operating systems
13:39and hibernates through its first lunar night.
13:43It wakes up on January 29, 2019.
13:47All its tools operate normally.
13:49The rover travels 390 feet
13:52during its first full lunar day.
13:54One lunar day lasts for about 14 days,
13:57and a lunar night has the same duration.
14:00Moving and exploring during the day
14:02and switching off during the night
14:04becomes the rover's routine.
14:06It's the 8th lunar day
14:08when U-2-2 stumbles across something incredible.
14:11This discovery makes the scientists
14:14put off all other plans for the mission.
14:16They focus on figuring out
14:18what the strange material found by the rover is.
14:22In the beginning,
14:23this lunar day is no different from any other.
14:25It begins on July 25,
14:28when the rover starts making its way
14:29through an area pockmarked with tiny impact craters.
14:33U-2-2 is helped and monitored
14:35by the driver team
14:37from the Beijing Aerospace Control Center.
14:40On July 28,
14:41the team is preparing to shut the rover down
14:43for a midday nap.
14:45The sun is high in the sky.
14:47It means there are high levels of radiation
14:50and scorching temperatures
14:51that can damage the machine.
14:53Before powering U-2-2 down,
14:55the scientists are looking through the pictures
14:58taken by the rover's main camera.
14:59That's when they spot it,
15:01a small crater filled with something
15:03that looks shockingly different
15:05from the surrounding landscape.
15:07Unable to identify the gel-like substance,
15:09the team orders the rover
15:11to check this bizarre finding.
15:13U-2-2 cautiously nears the crater
15:15to examine the weirdly colored stuff.
15:18The machine uses special equipment
15:20that detects the light reflected off the substance.
15:23It's supposed to help the researchers
15:25to understand the structure of the material.
15:27Unfortunately, the nature
15:30of the unusually colored finding
15:31has remained a mystery for over a year.
15:35No wonder that both the finding
15:37and the fact that initially
15:39there were no images of the enigmatic stuff
15:42sparked curiosity all over the world.
15:45The only available description of the substance
15:47was that it looked like a randomly colored shiny gel,
15:51something that's rather odd
15:53for the dusty, arid surface of the moon.
15:55But finally, the mystery seems to have been solved.
15:59The researchers have analyzed the information
16:01received from the rover's equipment.
16:03As expected, the substance turned out
16:06to be made up of rock,
16:07greenish and glistening breccia,
16:09in a sample no larger than 20 by 6 inches.
16:13It's kind of like a geologic version
16:15of jello salad with fruit inside.
16:18If you melt it down, it'll look glassy.
16:22Breccia consists of sharp stones
16:24joined together by a chalky substance.
16:26The sample found on the far side of the moon
16:29is made up of a mix of different minerals.
16:31The main is a type of silicate
16:34that's one of the most common components
16:36in both the moon and Earth's crust.
16:38The piece also contains some glass,
16:41which means it could have formed
16:42during a volcanic eruption.
16:44But volcanic activity on the moon
16:46stopped more than 3 billion years ago.
16:49That's why the researchers are almost sure
16:52it's unlikely to be the source
16:54of the unusual finding.
16:56The material could have been created
16:58by a massive asteroid, comet, or meteorite
17:01that once hit the moon.
17:03During the collision,
17:04the pressure and temperature were so high
17:06that huge amounts of rock instantly melted.
17:09Some pieces cooled down rapidly enough
17:12to form glass.
17:13The rest gathered at the center
17:15of the impact crater
17:16and grew colder more slowly,
17:18forming a new rock.
17:20The substance was likely not formed
17:22in the von Karmen crater,
17:24but in the nearby Finsen and Alder craters.
17:27The hollow where the rover made its finding
17:29was just 7 feet across.
17:31Whatever left it had to be no wider
17:33than an inch.
17:35But then, it would be too small
17:37to create such a large piece of breccia.
17:41It's interesting that the material
17:43is similar to the samples collected
17:45by the astronauts from NASA's Apollo missions.
17:48One of those samples
17:49was made of dark, broken shards of minerals
17:51glued together.
17:53It also contained some black, shiny glass.
17:56It's not clear, though,
17:58whether it's the same as the stuff
17:59discovered by U-2-2.
18:01When the rover took photos
18:03and made its measurements,
18:04it was rather dark in the area.
18:06The quality of the images isn't that great.
18:09The experts also explain
18:11that the mission is examining
18:13a previously unexplored area of the moon.
18:16That's why they don't have any samples
18:18from that region
18:18to compare them
18:20with the greenish, shiny substance
18:21U-2-2 found.
18:23But if their guesses turn out to be true,
18:25then the far side of the moon
18:27might have more in common
18:28with the Earth-facing one
18:30than we used to think.
18:32But what's so special
18:34about this dark side
18:35of Earth's natural satellite?
18:37And why can't we see it?
18:41It's all because of the phenomenon
18:43known as tidal locking.
18:45Earth's only natural satellite
18:47rotates around its axis
18:48once in 27 days.
18:50It's the same amount of time
18:52it needs to go around our planet.
18:54That's why you always see the same face.
18:57To be precise,
18:5859% of the moon's surface
19:00is visible to people.
19:01It means that you can catch glimpses
19:04of the satellite's far side
19:05at some times of the year.
19:07The moon's side we can't see
19:09is quite different
19:11from the one facing Earth.
19:12It doesn't have dark spots
19:14that are visible at night.
19:15Those are lunar basaltic planes
19:18called lunar meria.
19:20They were created
19:20by ancient volcanic eruptions.
19:22Those happened about
19:233 to 4 billion years ago.
19:26Instead of planes,
19:27the far surface of the moon
19:28has countless craters
19:30and tall mountains.
19:32One of the ideas
19:33about such a striking difference
19:34between the two sides
19:35is based on the collision theory.
19:38It claims that billions of years ago,
19:41Earth collided with another planet
19:42or some other massive space body.
19:45After that,
19:46the debris from this collision
19:47crashed with something
19:49that would later form our moon.
19:50That's why the satellite's landscapes
19:52differ so greatly.
19:56A more recent theory
19:57suggests that the Earth-facing part
19:59of the moon
20:00is warmer
20:01because of the heat
20:02radiated by our planet.
20:03During the period
20:05of volcanic eruptions,
20:06it was cooler
20:07on the farther side.
20:08That's why the minerals there
20:10became solid faster.
20:12They formed a protective layer
20:13shielding the moon's insides
20:15against the meteorites.
20:16But each impact
20:18left an impressive crater.
20:19At the same time,
20:21a much softer crust
20:22on the front-facing side of the moon
20:24spewed lava
20:25every time a meteorite hit it.
20:27After this lava cooled down,
20:29it covered the impact craters.
20:31Even though the far side
20:33is often called dark,
20:34both sides get almost
20:36the same amount of sunlight.
20:37The side we see
20:39looks a bit brighter
20:40because of the glow
20:41coming from Earth.
20:43There are two reasons
20:44why people are interested
20:45in exploring the far side
20:47of the moon.
20:48After leaving our planet,
20:50many radio waves
20:51get blocked
20:51by Earth's natural satellite.
20:53If astronomers
20:54could build their radio
20:55and optical telescopes
20:56on the dark side,
20:58they would get
20:59much more data.
21:00There would be no problems
21:01with any kind
21:02of interference.
21:03The telescopes
21:04would also be shielded
21:05from the glare of daylight
21:06coming from our planet.
21:08If telescopes
21:09were set up
21:09inside craters,
21:10they would also be protected
21:12from solar radiation.
21:14Astronomers
21:15would be able
21:15to get an incredibly
21:16clear view
21:17of the far regions
21:18of the universe.
21:19Plus,
21:20scientists believe
21:21there are great amounts
21:22of helium-3
21:23on the opposite side
21:24of the moon.
21:25Earth is protected
21:26from solar winds
21:27that carry this gas
21:29by its magnetic field.
21:30But our natural satellite
21:32doesn't have
21:33such a shield.
21:34That's why experts
21:35believe the moon
21:36can be a perfect place
21:38for helium-3 mining.
21:39This rare element
21:41can be later used
21:42as the fuel
21:43for fusion reactors.
21:45There are a few theories
21:47about how the moon
21:48appeared in the sky,
21:49and recently,
21:50a new idea
21:51has popped up.
21:52But before we discuss
21:54this newcomer,
21:55let's look at the most
21:56popular hypotheses
21:57of the moon's formation.
21:59The capture theory
22:00claims that Earth's
22:01natural satellite
22:02used to be
22:03a wandering body,
22:04something like
22:05a large asteroid.
22:06It had formed
22:07somewhere else
22:08in the solar system
22:09before it was captured
22:10by our planet's gravity
22:11when passing nearby.
22:13The accretion hypothesis
22:15suggests that the moon
22:16formed in orbit
22:17around Earth
22:18at the same time
22:19as our planet
22:19appeared in the darkness
22:20of the cosmos.
22:22Then,
22:23there's the fission theory
22:24that says that
22:25at one point
22:25in its development,
22:26Earth was spinning
22:27so fast
22:28that some of its material
22:30broke away
22:30and started to orbit
22:31the planet.
22:32And the giant impact theory,
22:34which is the most popular
22:36these days,
22:37claims that the moon
22:38formed during a collision
22:39between Earth
22:40and another hypothetical planet
22:42called Theia,
22:43which was way smaller,
22:44probably the size of Mars.
22:46The resulting debris
22:48collected in an orbit
22:49around Earth
22:50and formed the moon.
22:51And now,
22:52let's move to the new theory
22:54you've been patiently
22:55waiting for.
22:56According to it,
22:57our satellite
22:58might have formed immediately,
23:00in a matter of hours,
23:01after the collision
23:02between Earth
23:03and Theia.
23:04The material
23:05from the two planets
23:06was likely launched
23:07directly into Earth's orbit
23:08right after the impact.
23:10It formed the moon
23:12and left traces
23:13deep inside Earth.
23:15In previous scenarios,
23:17Theia's remains
23:18were thought to have been
23:18scattered all over space,
23:20mixing with just a bit
23:22of the material
23:22coming from our own planet.
23:24But then,
23:25why do we see
23:26such shocking similarities
23:28between the moon's
23:29and Earth's compositions?
23:31Could it be that Theia
23:32was isotonically
23:33and chemically similar
23:35to Earth?
23:36Unlikely.
23:37But according to the new theory,
23:39more material from Earth
23:41was used to create the moon,
23:43its outer layers in particular.
23:45It might explain
23:46this similarity in composition.
23:48One more theory
23:49also tries to explain
23:51this mysterious similarity,
23:52the Sinestia model.
23:54According to it,
23:55our satellite formed
23:57inside a swirl
23:58of vaporized rock
23:59left by the collision.
24:00But this theory
24:02can't explain
24:02the moon's current orbit.
24:04The new single-stage theory
24:06does offer us
24:07plausible explanations
24:08for both the similarities
24:10in composition
24:11and the orbit of the moon.
24:13It might also provide us
24:15with some answers
24:15to previously unsolved mysteries.
24:18Since this scenario
24:20puts the moon
24:20into a wider orbit
24:22and gives it an interior
24:23that is not fully molten,
24:25it can explain
24:26the satellite's tilted orbit
24:27and thin crust.
24:29In any case,
24:30to confirm one of these theories,
24:32we need to analyze
24:33future lunar samples
24:34that will be brought to Earth
24:36by NASA's upcoming
24:37Artemis missions.
24:39Scientists will be able
24:40to get their hands
24:41on some material
24:42from deeper beneath
24:43the moon's surface
24:44and compare if real data
24:46matches these simulated scenarios.
24:48In the past,
24:50the Apollo missions
24:51already brought back
24:52about a third
24:53of a ton of rock
24:54and soil
24:54from our satellite.
24:56These samples showed
24:57that Earth and the moon
24:58had some remarkable
24:59chemical similarities.
25:01They could only suggest
25:03one thing.
25:04These space objects
25:05had a linked history.
25:07If the moon
25:08had formed elsewhere
25:09and been captured
25:10by our planet's gravity
25:11later on,
25:12its composition
25:12would be very different
25:13from that of Earth.
25:14But if the moon
25:16had been created
25:17at the same time
25:18as Earth,
25:18or if it had broken
25:19off our planet,
25:21the type and proportion
25:22of minerals on the moon
25:23would be the same
25:24as on Earth.
25:25But they are
25:26a bit different.
25:27The moon's minerals
25:28contain less water
25:29than their terrestrial
25:31counterparts.
25:32The satellite
25:32is also richer
25:33in materials
25:34that form rapidly
25:35at high temperatures.
25:37That's why
25:38the most accepted model
25:39of the moon's formation
25:40these days
25:41is the giant impact model.
25:44Meteorites coming
25:44from the moon
25:45are a great source
25:46of data for studying
25:47the origins
25:48of our satellite, too.
25:50They can tell us
25:51even more about the moon
25:52than Apollo samples,
25:54all because such meteorites
25:55come from all over
25:56the surface of the moon.
25:58Meanwhile,
25:59Apollo samples
26:00were collected
26:00just in one place
26:02near the equator
26:02on the near side
26:03of the moon.
26:06There's something
26:07happening inside the moon,
26:09something that nobody
26:10expected.
26:11Not a dramatic shift
26:12you'd see on the outside,
26:14but deep down,
26:15where things seem
26:16frozen in time,
26:17scientists have uncovered
26:18a hidden layer
26:19of what you could only
26:20call moon goo.
26:23Remember those school
26:24lessons about the crust,
26:25mantle, and core?
26:26Much like the Earth,
26:28the moon is made up
26:29of layers,
26:29a crust, mantle,
26:31and core.
26:32However,
26:33the moon's core
26:33is much smaller
26:34compared to ours.
26:36Earth's core is huge.
26:38It makes up about
26:38a third of our entire
26:39planet's mass.
26:41The moon's core
26:42makes up only about
26:431-2% of its mass,
26:45and its diameter
26:46is about 1-5th
26:47the diameter
26:48of the moon itself.
26:49It's surrounded
26:50by a hard,
26:51rocky mantle.
26:52But it turns out
26:53that between
26:54these two layers,
26:55that mysterious
26:56goo layer,
26:57and it's way more
26:58important than you
26:59might think.
27:00The layer is soft
27:01and partially molten,
27:03ebbing and flowing
27:04like the tides
27:05in our oceans.
27:06It rises and falls,
27:08stretching and shifting
27:09as if it were alive.
27:10Its movement
27:11isn't chaotic,
27:12but subtle and regular.
27:14We always knew
27:15that the moon
27:16influences our seas
27:17and oceans,
27:18causing tides
27:19with its gravity.
27:20But it turns out
27:22that we influence it back.
27:24The goo ocean
27:25reacts to the
27:26gravitational dance
27:27between Earth
27:27and the Sun.
27:29Also,
27:30the molten layer
27:30could be made of
27:31ilmenite,
27:32a very intriguing material.
27:34Ilmenite is rich
27:35in titanium,
27:36a strong and lightweight
27:37metal that we really love
27:39over here on Earth.
27:40Titanium is used
27:41in everything,
27:42from airplane parts
27:43and spacecraft
27:44to medical devices.
27:46Even in everyday items
27:47like bikes
27:48and laptops.
27:49All because
27:50it's incredibly strong
27:51and very resistant
27:52to corrosion
27:53and heat.
27:54So,
27:54if the moon
27:55might have a molten layer
27:56rich in ilmenite,
27:58that would be awesome.
27:59Astronomers are already
28:01planning for lunar bases.
28:02And if we had a material
28:04to build structures,
28:05spacecraft,
28:06or even tools
28:06for astronauts
28:07right there,
28:08that would be
28:09a game-changer.
28:11Otherwise,
28:11we'd need to transport
28:12materials from Earth,
28:14which is extremely costly.
28:15This is our first
28:16tangible sign
28:17that the moon
28:18is not just
28:19a cold,
28:20boring rock.
28:21Instead,
28:21it's dynamic,
28:23living,
28:23and breathing,
28:24with moving forces
28:25beneath the surface.
28:27NASA used
28:28new special tools
28:29to discover this,
28:30the Gravity Recovery
28:31and Interior Laboratory
28:33and the Lunar Reconnaissance Orbiter.
28:36These are both
28:36space missions
28:37designed to study the moon,
28:39but they don't just
28:40look at the surface
28:41like a telescope.
28:42Instead,
28:43they help measure things
28:44we can't see
28:45with our eyes,
28:46like the moon's gravity
28:47and how it changes
28:48over time.
28:50GRAIL sent
28:51two small spacecraft
28:52around the moon
28:53named Ebb and Flow.
28:56The idea was
28:57for these spacecraft
28:58to fly close to each other
28:59and measure tiny differences
29:01in the moon's gravity
29:02as they go.
29:03It's like they were
29:04feeling the moon's
29:05invisible pull
29:06in different places.
29:07If the moon's gravity
29:09was stronger in one spot,
29:10the spacecraft
29:11moved closer together,
29:12and if it was weaker,
29:14they moved farther apart.
29:15This helps scientists
29:17understand what's going on
29:18inside the moon,
29:19even if they can't
29:20actually go there.
29:21And the spacecraft
29:22intentionally crashed
29:24into the moon
29:24in December 2012
29:26to end the mission.
29:27The Lunar Reconnaissance Orbiter
29:29is a bit different.
29:30It takes super-detailed
29:32pictures of the moon
29:33and collects other
29:34important information
29:35about its surface.
29:36By combining the information
29:38from both GRAIL
29:39and LRO,
29:40we were able to find
29:41this goo layer.
29:43But this discovery
29:44actually challenges
29:45everything we thought
29:46we knew about lunar geology.
29:48How did this molten layer
29:50get there?
29:50How long has it existed?
29:52And perhaps more fascinating,
29:54how it stayed warm
29:55for millions of years?
29:57That's a million-dollar question.
29:59The moon's core
30:00generates heat,
30:01just like ours.
30:02But it's not as easy
30:03as saying,
30:04oh, the core's heat
30:05probably keeps it
30:06warm and molten.
30:07Well, first,
30:09the moon's core
30:09is much smaller
30:10and less active
30:11than Earth's,
30:12meaning it produces
30:13significantly less heat.
30:15Plus, the moon
30:15is much cooler
30:16than Earth in general.
30:17With temperature dropping
30:19to minus 200 degrees Fahrenheit
30:20on the surface,
30:22how could this inner layer
30:23still stay
30:24in this flowing state?
30:25That's still a mystery.
30:27In any case,
30:28this goo
30:28could actually explain
30:30a lot of stuff
30:30about the moon.
30:31For example,
30:32astronomers were exploring
30:34moon quakes
30:35and how they happened.
30:36Now they think
30:37that it might be
30:37this semi-molten layer
30:39shifting and moving
30:40beneath the surface.
30:42Now, beyond the moon itself,
30:43it also tells us more
30:45about other celestial bodies.
30:47If the moon,
30:48something we considered
30:49basically a huge static rock,
30:51has such a dramatic life,
30:53what about other planets,
30:54moons, or asteroids?
30:56Could they also hide
30:57similar hidden movements
30:59beneath their surfaces?
31:00We can even understand
31:02our own planet better,
31:03learn more about how tides
31:05and similar stuff works.
31:06There are so many
31:07great discoveries
31:08we've been making
31:09on the moon.
31:10Recently,
31:11we found some awesome stuff
31:13beneath the surface.
31:14Massive caves
31:15hidden for millions of years.
31:17For over 50 years,
31:18scientists have suspected
31:20that the moon's surface
31:21is full of underground tunnels
31:23and caves.
31:24These are known as lava tubes
31:26because they were
31:27formed by lava.
31:28Duh!
31:29Millions of years ago,
31:30the moon was pretty unstable.
31:32It underwent some volcanic activity,
31:34causing eruptions.
31:35When a volcano erupts,
31:37lava can flow across the surface.
31:39As the outer layer
31:41of the lava cools and hardens,
31:43it forms a solid roof
31:44of dark material.
31:45It's actually what these
31:47famous dark spots
31:48on the moon are.
31:49These are dark,
31:50hardened remains
31:51of ancient lava.
31:52But the hot,
31:53molten lava
31:54continues to flow
31:55through the center.
31:56Once the eruption ends
31:57and the lava drains away,
31:59what's left behind
32:00is an empty,
32:01hollow tunnel,
32:02hence a lava tube.
32:04On Earth,
32:05we have lava tubes
32:06in places like Hawaii
32:07or Iceland,
32:08where volcanic activity
32:10has created
32:10similar underground tunnels.
32:12The same thing happened
32:13on the moon
32:14billions of years ago,
32:16although they're much crazier
32:17compared to ours.
32:18In fact,
32:19lunar lava tubes
32:20are now thought
32:21to be some of the largest
32:22and longest
32:22in the entire solar system.
32:24One such cave
32:26was discovered
32:26beneath the famous
32:27Mare Tranquillitus,
32:29the place where
32:30Apollo 11 first landed.
32:31And it's at least
32:32340 feet deep.
32:34Now,
32:35all these lava systems
32:36have remained hidden
32:37just beneath the surface,
32:38untouched
32:39for millions of years.
32:40Only now,
32:41they finally managed
32:42to prove their existence.
32:44Scientists from
32:45the University of Trenta
32:46in Italy
32:47found them using
32:48special radar technology
32:50and advanced computer methods.
32:52These techniques
32:53let you see underground
32:54by sending radar waves.
32:56The waves bounce back
32:57and give clues
32:58about what's hidden underneath.
33:00By analyzing
33:01the way these waves
33:02reflected back,
33:04the researchers
33:04could detect the shape
33:06and size
33:06of the hidden caves.
33:08Now,
33:08the best thing
33:09about this discovery
33:10is that we could build
33:11all our bases there.
33:13These caves
33:14protect from radiation,
33:15harsh winds,
33:16and meteoroids.
33:17NASA even found evidence
33:19that some of these caves
33:20stay at a steady
33:2263 degrees Fahrenheit.
33:24That's some crazy
33:25coziness for the moon.
33:26And on top of that,
33:27there could even be
33:28some water there.
33:30So,
33:30humans could take shelter
33:32inside these natural tunnels
33:33and build entire colonies
33:35on the moon.
33:36And I know what you're thinking.
33:37Could unexpected lunar monsters
33:40hide deep in those caves?
33:42Well,
33:42sure.
33:43There's a huge potential
33:44for exploring these caves
33:45and finding some awesome stuff.
33:48But even if we manage
33:49to find a miracle,
33:50like small life
33:51or microbial organisms,
33:53there's a 99% chance
33:55that there won't be
33:56actual animals or monsters.
33:58It would just be impossible
33:59for them to develop
34:00in such conditions.
34:01But it would make
34:03a great horror movie.
34:05Researchers want to send
34:07robots or drones
34:08to explore the tunnels first
34:09and then see
34:10if they're safe enough
34:11for humans.
34:12And it's not just the US
34:14getting in on the action.
34:15China is also investigating
34:17the possibility
34:18of using these moon caves
34:20as a future base,
34:21showing that the race
34:22to explore and settle
34:23the moon is eating up.
34:25with the lion's