00:00Did you know that the Moon is rusting?
00:02No, not rustic.
00:04Rusting.
00:05Well, that sounds impossible because rust needs oxygen.
00:08And the Moon, well, it doesn't have it.
00:11Or so we thought.
00:13Apparently, Earth is leaking its air, and it's marinating the Moon.
00:17It might have been like that for billions of years.
00:20What does this mean?
00:21And why do scientists say it's great news for a future lunar base?
00:25Well, let's find out.
00:27A few years ago, the Indian Space Research Organization sent a probe called Chandrayaan-1 to orbit the Moon.
00:35His mission was to take some nice pictures.
00:38But it also was carrying a NASA-built instrument designed to chemically map the surface.
00:43The readings came back showing something scientists didn't expect on the Moon.
00:48Hermatite.
00:49It's an iron oxide, or in plain words, rust.
00:53It's the same red, rusty material that eats through your garden fence or a forgotten bicycle chain.
00:59Finding rust on Earth is normal because our planet is wet and airy.
01:04You need a strict recipe to make it happen.
01:06You need iron, you need water, and you need oxygen.
01:10The Moon already has the first ingredient for rust because its surface is rich in iron from billions of years
01:16of asteroid impacts.
01:17But the other two ingredients are missing.
01:21There is no atmosphere to provide oxygen, and there is no liquid water gathering on the surface.
01:27But it goes beyond that.
01:29Space actually hates rust.
01:31The Sun constantly blasts the Moon with the solar wind, a stream of fast particles made mostly of hydrogen.
01:38Well, these particles tend to strip oxygen away from rocks instead of adding it.
01:43All of that makes it obvious why hermitite doesn't belong anywhere near our satellite.
01:49But these results don't lie.
01:51The presence of hermitite means that somehow, despite the vacuum in the Sun's particle stream,
01:58the Moon is getting a steady supply of oxygen.
02:01It's not coming from deep space or the lunar core.
02:05Also, the rust isn't spread evenly.
02:07The data showed that the hermitite is more concentrated on the side of the Moon that faces Earth.
02:13The far side is mostly clean.
02:16Now, the only oxidizer close enough to do the job is Earth.
02:20We learned at school that Earth's atmosphere ends at the Karman line, about 62 miles up.
02:26That's where space officially begins.
02:29But that's just the thick part.
02:31In reality, Earth is wrapped in a gigantic, invisible cloud of hydrogen called the geocorona.
02:38It's enormous.
02:39It glows in ultraviolet light, and it searches almost 400,000 miles into space.
02:44That's farther than the Moon's orbit.
02:47This means that despite being very far away, the Moon is still within the outer edges of Earth's atmosphere.
02:54If you were standing on the Moon, looking back at Earth with a telescope that can see ultraviolet hydrogen,
03:01Earth wouldn't look like a blue marble.
03:02It would look like it's wearing a huge, fuzzy, glowing halo.
03:06Now, when we picture Earth and the Moon, we imagine a huge, clean gap between them.
03:12Two worlds separated by nothing.
03:14But that nothing isn't actually empty.
03:17The two are already connected by gravity, tugging on each other non-stop.
03:22But there's another kind of connection most people never think about.
03:27Earth is surrounded by an invisible force called a magnetic field.
03:31It's created deep inside the planet and stretches far out into space.
03:36We don't see it, but it's the reason compasses work and the Sun doesn't strip our atmosphere away.
03:41This magnetic field doesn't just stop at Earth's surface.
03:45It doesn't sit there like a perfect bubble, either.
03:47The solar wind pushes on it non-stop, stretching it out behind Earth into a long magnetic tail
03:54that reaches hundreds of thousands of miles into space, like a tail trailing behind a moving comet.
04:01That tail is how Earth's oxygen ends up on the Moon.
04:05The Sun slams into Earth's upper atmosphere, knocking oxygen and nitrogen atoms loose
04:10and turning them into charged particles.
04:13Normally, they'd drift off into space.
04:15But because they're charged, Earth's magnetic field grabs them and sends them backward, down the magnetic tail.
04:23Most of the time, the Moon is off to the side doing its own thing.
04:27But once a month, right around the full Moon, it slides straight into Earth's magnetic ponytail.
04:34Inside that tail, Earth blocks the harsh solar wind and gives the Moon a few days of calm.
04:40But it's still moving straight through particles leaking from Earth.
04:44Those particles collide with the surface and react with the iron in the soil.
04:49Repeat that long enough, and it adds up.
04:52Earth loses tiny traces of its air, and the Moon quietly collects them,
04:57using its weak gravity like a slow, patient net.
05:00It's like driving behind a dirty truck.
05:03Dirt flies off of it, but you don't really notice until it starts sticking to your windshield.
05:07The same thing happens on the Moon.
05:10Except, you know, no windshield.
05:12We actually have proof of this happening in real time.
05:16A Japanese probe called Kaguya was hanging out in lunar orbit,
05:20and its sensors spiked when the Moon passed through Earth's magnetic tail.
05:24It detected a surge of high-energy oxygen ions.
05:29Scientists call it the Earth wind.
05:30It acts like the solar wind, except instead of being hot particles from a star,
05:35it's made from leftovers of our own atmosphere.
05:39And this suddenly makes the Moon part of a much bigger story.
05:43Scientists think this kind of atmospheric escape can help explain what happened to planets like Mars.
05:49The red planet doesn't have a global magnetic field today.
05:52But long ago, it probably did.
05:55When that shield failed, its atmosphere had a much easier time leaking away.
06:01Studying Earth and the Moon is like watching a version of that process on replay, just in slow motion.
06:07And it's not unique.
06:09Near the edge of the solar system,
06:11Pluto's thin atmosphere is slowly being stolen by its moon, Charon.
06:16Ooh, larceny in space.
06:18Pluto's gravity is so weak that its atmosphere stretches far into space.
06:22When those gas particles drift close enough, Charon's gravity simply grabs them.
06:28No magnetic field needed, just a leaky planet and a nearby Moon pulling the material away.
06:34Now, when the Apollo astronauts brought lunar soil to Earth,
06:38it was already loaded with hydrogen from the solar wind.
06:41The Sun sprays the lunar surface with hydrogen,
06:44and over time, that hydrogen gets baked straight into the dust.
06:48That's the H.
06:50But you still need the O2 to create water.
06:53The regolith may already contain trace amounts of oxygen locked into minerals and dust.
06:59Not as ice, but as something that can potentially be processed.
07:03It would mean that regolith is not just a nuisance that destroys gear and rovers.
07:08For a future lunar base, even small amounts matter.
07:12Water is heavy.
07:13Launching it from Earth is a nightmare.
07:15If the Moon can supply even part of what astronauts need, it could make a difference.
07:22Now, another cool side effect of this discovery is that drilling into the Moon could tell us more about Earth's
07:28history.
07:29You see, our planet is terrible at keeping records.
07:32It's like a giant recycling machine.
07:34It's always changing.
07:36Tectonic plates grind the crust down and melt it into magma.
07:39Winds and rains erode rocks.
07:42The air that we breathe now is different from the one that was around 2 billion years ago.
07:47Now, we can guess what the ancient atmosphere was like, but we don't have a physical sample.
07:53The Moon is the complete opposite.
07:55It's cold and static.
07:57When those Earth particles land on the Moon, they get buried under dust and stay there.
08:02They're trapped in the crystal lattice of the soil.
08:05Think of the lunar surface like an ice core in Antarctica.
08:08The deeper we dig, the further back in time we go.
08:12If we drill a core sample on the Moon, we might, theoretically, find layers of oxygen and nitrogen from 2
08:19.5 billion years ago.
08:21That is right around the Great Oxidation Event, when microbes first started pumping oxygen into our atmosphere.
08:28That could tell us something we don't know.
08:30It could prove that life started earlier than we thought.
08:34It could show us exactly how a dead planet turns into a living one.
08:38That's another answer you can give the next time somebody asks why we should go back to the Moon.
08:44Also, to find the green cheese.
08:46Hey, just Google it.
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