The Far Side Of The Moon Is Not What Think

Added: 2026-05-10

[00:00:00]The dark side of the moon has been lying to us.

[00:00:03]Not about being dark. That part's the lie everyone already knows.

[00:00:08]We've all heard the correction.

[00:00:10]Actually, it gets just as much sunlight as the near side.

[00:00:14]The term came from unknown, not unlit.

[00:00:17][music] Fine. That's the trivia you bring up at parties, but here's the part nobody mentions. The far side is brighter.

[00:00:26][music] Visibly, measurably brighter. The dark never meant unlit. It meant unknown.

[00:00:34]>> [music] >> And we've been calling it the wrong thing for 60 years. But that's just the beginning of what we got wrong.

[00:00:40]Because when we finally saw the far side, not with human eyes, not at first, but with a camera cobbled together from pieces of a crashed American spy balloon, what came back wasn't just unexpected.

[00:00:52][music] It was impossible to square with what we thought we knew about how moons form.

[00:00:58]Let's start with how we got there.

[00:01:01]Because that's where the first crack appears.

[00:01:04]October 7th, 1959.

[00:01:07]Luna 3, a Soviet spacecraft weighing 278 kg, swings around the moon and fires its camera.

[00:01:16]Not a digital sensor, film.

[00:01:19]35-mm film, reportedly salvaged from American Genetrix spy balloons that had been shot down over Soviet territory, then hardened against radiation because space, it turns out, is very good at destroying things.

[00:01:34]The camera shoots 29 frames. 17 are usable.

[00:01:39]The film develops inside the spacecraft.

[00:01:42]There's a darkroom in orbit. And then gets scanned line by line and beamed back to Earth as a radio signal.

[00:01:50]Six photos are published, and they show something no one was ready for. The The side of the moon, the one we've stared at for all of human history, >> [music] >> is smooth in places, dark in others, covered in those flat volcanic planes.

[00:02:05]The far side, cratered to oblivion, beat up, [music] smashed, ancient.

[00:02:11]Bill Anders, orbiting aboard Apollo 8 in December 1968, described it like, "A sand pile my kids have played in for some time.

[00:02:21]It's all beat [music] up, no definition, just a lot of bumps and holes."

[00:02:26]Here's what didn't make sense. It's the same moon, formed from the same debris cloud after the same giant impact 4 and 1/2 billion years ago.

[00:02:35]The near side and far side should look like siblings.

[00:02:39]>> [music] >> They don't. They look like different planets. So, what happened?

[00:02:44]Let's talk about the crust first, because that's where the asymmetry starts to get measurable.

[00:02:50]On the near side, the crust averages 30 to 40 km thick. On the far side, 50 to 60 km.

[00:02:58]In some places, 80.

[00:03:01]The crust isn't just thicker, >> [music] >> it's doubled. And that thickness had consequences.

[00:03:07]When the moon was young and still cooling, magma from the interior tried to rise to the surface.

[00:03:13]On the near [music] side, where the crust was thin, it broke through.

[00:03:18]Lava flooded the lowlands, filled the impact basins, cooled into those dark planes we see today.

[00:03:25]Volcanic resurfacing.

[00:03:28]On the far side, the magma couldn't punch through.

[00:03:31]The crust was too thick.

[00:03:33]So, it stayed underground, trapped.

[00:03:36]The far side never got resurfaced.

[00:03:40]What you're looking at when you see those craters, some of them are 4 billion years old.

[00:03:46]The far side is a time capsule.

[00:03:49]The near side got a makeover.

[00:03:51]The far side didn't.

[00:03:53]But that just raises another question.

[00:03:56]Why is the crust thicker in the first place?

[00:03:59]Nobody's completely sure.

[00:04:02]The leading theory involves an impact.

[00:04:05]Not the one that formed the moon, a second one hundreds of millions of years later.

[00:04:11]The South Pole Aitken Basin, 2 and 1/2 thousand kilometers across, 8 kilometers deep. It's the largest confirmed impact structure in the entire solar system.

[00:04:23]The asteroid that carved it out hit the far side 4.25 billion years ago.

[00:04:28]Only 320 million years after the solar system itself formed.

[00:04:34]And it didn't just leave a crater.

[00:04:36]>> [music] >> In 2019, researchers analyzing data from NASA's GRAIL mission found something under the South Pole Aitken Basin >> [music] >> that shouldn't be there.

[00:04:46]A mass anomaly.

[00:04:48]Buried hundreds of kilometers underground.

[00:04:52]2.18 * 10 to the 18th kilograms of something denser than the surrounding rock.

[00:04:59]The paper described it like this.

[00:05:02]As if a pile of metal five times larger than the Big Island of Hawaii was sitting under the surface.

[00:05:09]Two possibilities.

[00:05:10]Either it's the iron-nickel core of the asteroid that hit, still embedded in the moon's mantle after 4 billion years.

[00:05:18]Or it's a concentration of dense ilmenite-rich oxides, leftover material from when the moon's magma ocean solidified.

[00:05:26]Neither theory has been ruled out. We still don't know what it is.

[00:05:31]But here's where it gets stranger.

[00:05:33]That impact, the one that created South Pole Aitken, the one that maybe left a chunk of asteroid core in the moon's guts, might have done something else.

[00:05:43]It might have excavated material rich in radioactive elements, preferentially throwing it toward the near side.

[00:05:51]>> [music] >> Potassium, rare earth elements, phosphorus, creep, they [music] call it. Creep is a heat source.

[00:06:00]And if the near side ended up with more of it, >> [music] >> that side would have stayed hotter longer, which means more volcanism, which means thinner crust, more maria, a younger surface.

[00:06:12]The moon isn't symmetric, and we're still piecing together why.

[00:06:16]Let me give you one more number, because this one rewrites what we thought we knew about the moon's internal structure.

[00:06:24]In 2025, scientists analyzing tidal data from GRAIL measured the temperature of the lunar mantle at depths between 800 and 1,250 km.

[00:06:35]The near side is still 100 to 200° Kelvin hotter than the far side, not at the surface, deep inside. [music] The asymmetry runs through the entire body of the moon, and then there's the water, or the lack of it. The far side mantle contains between 1 and 1 and 1/2 micrograms of water per gram of rock.

[00:06:59]That's among the driest values ever measured for any planetary mantle.

[00:07:03]>> [music] >> The near side is orders of magnitude wetter.

[00:07:06]Why?

[00:07:07]Depending on who you ask, it's either because the far side lost its volatiles during the South Pole-Aitken impact, or because the moon's magma ocean crystallized asymmetrically and sequestered water on the near side.

[00:07:21]The data doesn't yet distinguish between those options.

[00:07:25]What we know for sure is this.

[00:07:28]The far side is bone [music] dry, and it has been for billions of years.

[00:07:33]Now, none of this would matter, none of it would even be visible, if the moon weren't tidally locked to Earth.

[00:07:40]Here's how that works.

[00:07:42]The moon's center of mass is offset slightly toward Earth.

[00:07:46]Not by much, but enough.

[00:07:49]That offset, combined with Earth's gravitational pull, >> [music] >> created a permanent torque. Over millions of years, that torque slowed the moon's rotation until one side always faced us.

[00:08:02]Tidal [music] locking.

[00:08:03]It's why we only ever see the near side.

[00:08:06]It's why the far side stayed hidden until 1959.

[00:08:10]>> [music] >> But it also means the moon's day is the same length as its orbit.

[00:08:15]29 and 1/2 Earth days of sunlight, then 29 and 1/2 days of darkness.

[00:08:21]The far side doesn't stay dark. It just stays away.

[00:08:25]And Earth's not done with the moon yet.

[00:08:28]The moon is still [music] receding.

[00:08:31]38.2 mm per year.

[00:08:34]In a few billion years, long after the sun expands into a red giant and incinerates [music] both of them. Earth will become tidally locked to the moon, too.

[00:08:44]One side of Earth will always face the moon.

[00:08:47]The other side never will.

[00:08:50]But that's a problem for a planet that won't exist.

[00:08:53]Let's talk about what we've actually put on the far side.

[00:08:57]Because for all the mystery, for all the asymmetry, >> [music] >> humans didn't set foot there.

[00:09:02]We still haven't. The first spacecraft to land on the far side was Chinese.

[00:09:06][music] Chang'e 4.

[00:09:09]January 3rd, 2019, at 2:26 UTC.

[00:09:14]It touched down in Von Kármán crater, deployed a rover called Yutu-2, >> [music] >> and started driving.

[00:09:21]Yutu-2 has now traveled 1,613 m >> [music] >> over 7 years. It's still going.

[00:09:29]The lander itself did something nobody talks about much. It ran [music] a SETI search.

[00:09:34]A a survey looking for signals in a frequency range that's completely drowned out on Earth >> [music] >> by FM broadcasts and satellite noise.

[00:09:44]The far side is the quietest place in the inner solar system.

[00:09:48]They didn't find anything.

[00:09:50]A 2026 preprint reported null results.

[00:09:54]But the fact that they [music] looked, that tells you something about what the far side offers.

[00:09:59]Silence.

[00:10:00]>> [music] >> Here's what changed in 2024.

[00:10:04]On June 2nd, >> [music] >> Chang'e 6 scooped up 1,935.3 g of regolith from the far side and brought it back to Earth.

[00:10:14]First sample returned from that hemisphere.

[00:10:17]The rocks [music] showed something unexpected. Magnetic signatures indicating the lunar dynamo, the moon's internal magnetic field, which we thought died 3 billion years ago, might have restarted [music] briefly around 2.8 billion years ago.

[00:10:32]Why? Nobody knows.

[00:10:35]A dynamo requires a liquid core and some kind of convection. [music] The moon's core is tiny, mostly solid.

[00:10:43]What could have reactivated it for a few hundred million years, then shut it down again?

[00:10:48]The samples don't answer that.

[00:10:50]They just ask the question louder.

[00:10:52]And now, we're going back.

[00:10:55]April 1st, 2026.

[00:10:57]Artemis 2 launches. Four crew members.

[00:11:00]Reid Wiseman, Victor Glover, Christina Koch, Jeremy Hansen.

[00:11:05]Their spacecraft [music] is called Integrity. It won't land. It's a flyby.

[00:11:10]A loop around the [music] moon, passing within 6,545 km of the far side.

[00:11:17]Closer than any humans [music] have ever been to it.

[00:11:20]On April 6th, they'll set a record.

[00:11:23]252,756 miles from Earth. Farther than anyone since Apollo 17 in 1972.

[00:11:32]But they won't touch the surface. That's Artemis 4.

[00:11:36]Early 2028, if the schedule holds.

[00:11:40]Neither the American Artemis program nor the Chinese-Russian ILRS initiative plans crude far side surface operations until the 2040s.

[00:11:50]For now, the far side belongs [music] to robots.

[00:11:53]Here's the part that gets me. The far side of the moon is the calibration standard for half the solar system.

[00:11:59]Every crater counting age estimate for Mars, Mercury, Vesta, the [music] asteroids, every conclusion about when life could have arisen on Mars, when Venus lost its water, >> [music] >> when the late heavy bombardment happened, all of it traces back to radiometric dates from lunar samples. And most of those samples are from the near side.

[00:12:20]We've been using one half of the moon to [music] date the rest of the solar system.

[00:12:25]The other half, older, less disturbed, [music] geologically frozen, might tell a different story or confirm the one we have.

[00:12:35]But until we sample it properly, we're extrapolating from incomplete data.

[00:12:40]There's one more thing the far side offers, and it has nothing to do with the moon itself.

[00:12:46]It's the only place in the inner solar system where you can observe the cosmic dark ages.

[00:12:51]>> [music] >> Before the first stars formed, the universe was filled with neutral hydrogen.

[00:12:57]That hydrogen emitted a faint radio signal at 21 cm, but from Earth, we can't [music] see it.

[00:13:04]The ionosphere blocks it.

[00:13:06]Satellites drown it out.

[00:13:09]We're too loud.

[00:13:10]The far side isn't.

[00:13:12]In September 2026, NASA plans to land a radio experiment called LUSINE four antennas, 3 m each, deployed on the surface. It'll listen during the lunar night, when the moon itself [music] blocks all the radio noise from Earth.

[00:13:30]If it works, we'll be able to see back to a time before galaxies existed, before stars, [music] when the universe was dark and the only light was the fading afterglow of the Big Bang.

[00:13:42]That's what the far side offers, not mystery for mystery's sake, a view unobstructed by everything we've built.

[00:13:51]So, what is the far side really?

[00:13:53]It's not the dark side. It's not the hidden side anymore, either.

[00:13:57]>> [music] >> We've photographed every square meter of it.

[00:14:00]But, it's not like the near side. It never was. Thicker crust, bone-dry mantle, a buried mass anomaly the size of Hawaii, >> [music] >> internal heat that still hasn't equalized after 4 billion years, a surface that never got resurfaced, craters that date back to when the solar system was a teenager, and we're only starting to understand why. [music] The moon formed from one impact, but it was shaped by others.

[00:14:29]The South Pole-Aitken collision, the tidal lock with Earth, the asymmetric [music] distribution of heat-producing elements. Every one of those events left a mark, and the far side absorbed most of it.

[00:14:43]It's not what we thought it was when we first saw [music] those grainy photos in 1959.

[00:14:48]It's older, stranger, and in some [music] ways more important than the side we've been staring at for all of human history.

[00:14:57]Because the near side is the face the moon shows us, but the far side is the one [music] it keeps.