00:00Hey, space fans, it's Tarek Malik, Editor-in-Chief of Space.com.
00:03And on this week in space, we talked to former NASA Chief Scientist Jim Green about the early days of the moon,
00:09how it broke off from Earth and what things were like in those early days. Check it out.
00:14So if my dumbbell math was correct, and the reason Tarek and I have to think about these things so much harder than you do
00:21is because our math scores weren't particularly high once we got to higher mathematics in the university.
00:26But everybody who listens to the show knows that already.
00:28The moon, way back when, when it was much closer for Earth radii, would have been like 20,000 miles or so above,
00:37which would make it very large in the sky. That would be a whole different experience, wouldn't it?
00:41Yeah, yeah, it would be. If you could stand the heat of the surface, if you were on the surface,
00:47the moon would just be enormous, 16 times what it is today in size.
00:52And it already looks kind of big, but I mean, it would really be huge.
00:57I think we'd be fearful that, you know, it looks like an object's going to come and hit us.
01:03But over time, it moves away.
01:06The other fascinating thing about these samples that we have from the Apollo
01:12is we're continually analyzing them.
01:15And one of the things that we have found is that they have what's called a remnant magnetic field in them.
01:22And so for more than 40 years, the controversy is, well, where did it get the field?
01:29Did it get it from impacts that occur?
01:33Does it get it, does the moon actually generate its own magnetic field?
01:38You know, and we now have pretty well solved that, which to me was really exciting.
01:45Well, that was, yeah, that was something I really wanted to ask you.
01:48Because by the way, I think we forgot to mention specifically that the article that Rod was talking about,
01:54you've got this article all about volatiles on the moon and the moon's history and its birth in,
02:01it's in Ad Astra?
02:02Is that right, Rod?
02:03No, actually, Jim sent it to me.
02:05It's in Room.
02:06Yeah, it's in Room.
02:07Room.
02:08Yeah, yeah, yeah.
02:09Yeah, so.
02:10That other cool space magazine.
02:12Exactly.
02:12It is a cool space magazine.
02:13Yeah.
02:15At Astra, I'll have to publish something in that next.
02:18Anytime, my friend.
02:20Okay.
02:20I'm waiting.
02:20All right.
02:21Okay, okay.
02:22I got some ideas.
02:24I mean, I always love me a giant impact hypothesis when it comes to like the moon's formation
02:29and how it looks so similar to the Earth.
02:31I was really struck in your piece about looking for how certain types of volatiles that I never
02:38thought about, nitrogen, for example, I think, because we're talking about magnetic fields,
02:42actually end up in the regolith of the moon.
02:48Because you described that in that early phase, when it's, you know, the moon is its solitary body,
02:55a separate body, but it's still kind of not very far away, that it had this magnetic field.
03:00I would assume because it's still also got a molten core or what not.
03:04Correct.
03:05Is that right?
03:05Correct.
03:05Correct.
03:06Yeah.
03:06But that it's also mixing with the Earth's magnetic field, which I assume was much bigger,
03:11that allowed material to keep on transporting to the moon, despite the fact that the impact
03:18was over with.
03:18That just boggles my mind, and I don't understand how that works.
03:21And I was wondering if you could explain to my brain how that works.
03:25Sure.
03:26So magnetic fields are really wonderful highways for charged particles.
03:33And the lower the energy, the more closely they are connected to the magnetic field and follow
03:40them very closely.
03:42And so, indeed, the Earth had a magnetic field.
03:45We still do today, thank goodness.
03:47That stretched all the way back to its early formation.
03:51The rock record on the moon indicates, indeed, that the moon had a magnetic field, which makes
03:58it a magnetosphere.
03:59And because the moon is so close, the moon's magnetosphere is inside the Earth's magnetosphere
04:06for several hundred million years, perhaps.
04:11And so what's happening is those two fields get interconnected.
04:16And when they do, then material from the Earth will run down that magnetic field and precipitate
04:25into the lunar environment.
04:27That's where that field line tells them it's going to go.
04:31Now, this configuration early on is exactly the kind of configuration we see with Europa
04:39in Jupiter's magnetosphere.
04:43So the more we know and study what happens between Europa and Jupiter and how their magnetic fields are
04:51interconnected, the more we'll understand what the early Earth and moon's magnetosphere was like.
04:58But what happens is early on, the sun was very active, coronal mass ejections all the time, far more than we have today.
05:09Huge sunspots.
05:11And it produced a lot of energy in the ultraviolet and x-rays.
05:18And as it does that, what happens is it heats the atmosphere, which expands, and also ionizes the upper part of the atmosphere,
05:30creating the layer we call the ionosphere.
05:33Well, that is going to move out.
05:36It's like, here's another math thing.
05:40You've got a lot of pressure here, low pressure there, and therefore, that material is going to move from high pressure to low pressure.
05:50It's got something to do with thermodynamics, all right?
05:53Well, the ionized ionosphere material is just going to run down that field line.
06:00And if that field line runs all the way to the poles of the moon, which it does in this case,
06:05then the regolith on the moon is going to be hammered with material from the upper atmosphere of the Earth.
06:12That's so weird.
06:13Now, that means all the nitrogen and some of the things that we also found in the lunar rocks,
06:19and we couldn't figure out where the nitrogen is coming from.
06:22It's not coming from the solar wind.
06:25You know, far more nitrogen was there than we would expect from the solar wind.
06:31It had to come from somewhere.
06:32Well, it's coming from the Earth.
06:33Yeah.
06:34And it came probably during the time the moon had a magnetosphere.
06:41By the way, I forgot to ask, too, why is nitrogen so weird?
06:45Like, how do you rule out solar wind?
06:46Is it because it needs earthly processes to be found naturally?
06:50Yeah.
06:51Well, nitrogen is in the solar wind, but in an extremely low amount.
06:57No, I see something as more of it.
06:59Yeah.
06:59So, it's about its ionization state.
07:03It's also about the quantity.
07:06And so, those add up to mean that additional nitrogen is there well beyond what would be in the normal solar wind impacting the moon and absorbing that solar wind.
07:23Well, the magnetosphere, just like we are protected from the solar wind, now the moon is protected by the solar wind.
07:33And so, processes that we're familiar with on the moon or here on Earth are now happening on the moon.
07:41So, now that means if the moon is outgassing, which it does, and it still does today, like all our planets are still outgassing.
07:50They're still cooling off from when they were made, we're not dead, you know, inside, we're still very active.
07:57Very active, and that's true on the moon, then the magnetosphere of the moon is going to hold that material in.
08:03It's going to hang on to an atmosphere that's being created as the moon outgasses, or even as the moon becomes more volcanically active.
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