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  • I think this is the only collections tour I've been on where I've been handed gloves.

  • Hey! We're here with Jim Holstein, who's theyou're the collection manager... - Collection manager, right.

  • - of meteorites. - Meteorites, mineralogy, jewelry, and gemstones.

  • But mainly meteorites 'cause that's our most popular exhibit.

  • - What is a meteorite? - What do you think a meteorite is?

  • - A meteorite is a part of a planet that was blasted off, that came through space, through the atmosphere, and landed on Earth.

  • - Okay, that's... - Is that kinda close? - That's close enough.

  • I mean you could have my job- that's all you need to know, actually. That's it. - That's— oh, alright.

  • - But meteorites, yeah, these are the rocks that fall from space when they're found on the surface of the earth.

  • We have three terms: a meteoroid is when it's floating around in space;

  • when it's making that streak through the atmosphere, they call that a meteor;

  • and then when you pick up the rock from the ground they call that a meteorite.

  • - Nice. And then there are different kinds of meteorites. - Right. There are three broad categories of meteorites.

  • You have stony meteorites, which are made out of...? - Stone

  • - Iron meteorites which are made out of— - Iron. Iron. - Oh you're jumping ahead!

  • - And stony-iron meteorites which are made out of...? - Both stone and iron! - Yes!

  • - I am an expert! - You are an expert.

  • And so when these things were originally formed at the beginning of our solar system

  • about 4.5 billion years ago, you had two broad categories of stony meteorites.

  • You have chonditic meteorites and achondritic meteorites

  • - Okay, I don't know what those are. - Yeah. So now we're getting a little bit deeper now.

  • Chondritic meteorites are from planetary bodies that are undifferentiated.

  • - Now what does that mean? - Yeah I don't know what that means. - Let's go to the board!

  • - Yay!

  • - Ok, so in the middle of the earth, you have what is called the...? - Core.

  • - Yes. Core. - I didn't know I was going to be quizzed today.

  • - You have to earn this. Outside the core you have the what?

  • - Uh, not the mantle...

  • - No, you're right, it is the mantle - Is it? It is the mantle? Ok.

  • - And that's my good spelling. And on the outside, the very thin layer, we call that— - The crust!

  • - The crust. So core, mantel, crust. That's a differentiated body.

  • Some of these meteorites actually came from differentiated bodies out in the solar system.

  • These are differentiated bodies that broke apart.

  • So for example we talked about the three basic typesthe iron, the stony, and the stony-iron meteorites.

  • The iron meteorites are actually samples of the cores of these planetary bodies that are differentiated.

  • - So how do you get a core from a planet? I mean that'd have to be a pretty gigantic impact,

  • or is it like spit up? -Yeah, absolutely. No no, ok so back to the board again.

  • What's a good color for the sun?

  • - Red.

  • - I guess, I don't have any yellow.

  • So here we have the sun. S. - That's a tiny sun.

  • - And we'll do the planets in blue.

  • Then we have closest to the sun, we have an orbit, and a planet called Mercury, right? - Mercury.

  • And that is, what? - Venus. - Venus.

  • And after that we have - It's earth - Yeah it is earth. Yeah, yeah, clearly it's earth.

  • And then beyond earth, we have what? - Mars.

  • - Mars, the red planet, Mars.

  • And then out beyond Mars we have what? What's the next one after Mars?

  • - Um, see I have to keep going through "my very enthusiastic mother"... Jupiter.

  • - Jupiter!

  • Jupiter is out here. But there's this gap here between Mars and Jupiter.

  • And in this gap is the asteroid belt

  • so we have asteroids, and these are all these failed planetary bodies that broke apart.

  • And a lot of these were impacting each other.

  • And these are all in orbit around the sun at this point.

  • So when they get impacted by another asteroid, it puts it on a different orbit

  • which puts it in an elliptical around the sun, and sometimes,

  • that elliptical orbit crosses the earth's orbit, so when the earth is going around

  • its own orbit, it would sometimes hit the orbit of one of these asteroids, or meteoroids

  • and then you have a very frowny-faced Earth

  • Awww - that gets hit by an asteroid.

  • We have about 80,000 tons of material that enters the atmosphere every single year.

  • Really - Most of it is dust size.

  • And you have maybe one or two events, car size object that hits the earth, and most of it hits the ocean.

  • Differentiated bodies: core, mantel, crust. - Yeah

  • - But that doesn't comprise the majority of meteorites that we have.

  • The majority of meteorites we have are these stony chondritic meteorites which come from undifferentiated bodies

  • - So one all homogeneous lump? - One all homogeneous things

  • And these comprise of about, almost 90% of all meteorites that are found on earth.

  • - Wow. Oh, well that's pretty.

  • - And what's special about those is that um, it didn't differentiate, which means

  • that it has all the metal still in the rock.

  • It's a very homogeneous piece of all metals, minerals, all mixed together

  • If you hold it in the right light - Yeah You see little flakes of metal in there

  • - It's shiny. - It's very sparkly.

  • - Can you see it? Why is it dark on the outside?

  • - That's called fusion crust, and that's what happens when the thing enters the atmosphere.

  • And as the atmosphere gets super heated, melts the outside and that becomes black.

  • You also get those indentations you see on the outside

  • those indentations are caused by atmospheric heating as well.

  • And so that these undifferentiated meteorites

  • are the most common ones, and um,

  • back in early history of the solar system, these would eventually in some cases heat up,

  • and become differentiated. Earth was an undifferentiated body at one time,

  • and then it heated up to the point where all the metal went to the core

  • and by mass it all sort of differentiated out, it separated itself out.

  • - Wow. That is amazing. My mind is being blown right now.

  • - So stony iron meteorites.

  • These comprise of less than 1% of all falls or finds.

  • - And this is the one that has both rock and iron in it? - Mhm.

  • - It's beautiful. - You can see these uh, nicely formed mineral grains.

  • These are actually crystals, they're actually gemstones that are embedded in this metal matrix.

  • - So what kind of gem stones are you-- - You usually see olivine, and it's a very common gemstone on earth.

  • These are formed deep in the mantel, and a meteorite like that, one of the theories is that

  • it was actually formed at the core mantel boundary, so

  • we had the illustration of the differentiated bodies--the core and mantel

  • The idea is that you get intermixing between the core and mantel, and when that body fell apart, that's how they harden

  • they harden they cool, they crystalize, and they um, froze out with the minerals embedded in the metal.

  • Let's talk about Mars! - I wanna talk about Mars.

  • Ok, so we talk about the rarity of these things,

  • and I talk about how the stony irons are the rarest of the three broad categories

  • but there's rarer objects still, and these Martian meteorites are in fact

  • - Oh my gosh. - One of the rarest types of meteorites.

  • - This is a piece of Mars. - That is a piece of Mars. This fell in 2011 in Morocco.

  • - So what does this tell you about Mars?

  • - So basically when an object hits Mars, it actually excavates a part of Mars out of it

  • and this actually came all the way from Mars so it tells a lot about the mineralogy.

  • How do we know it's from Mars? That's the biggest question.

  • - Yeah. - For example, the lunar meteorites that we have collected on earth

  • we're able to match those up geochemically to the lunar meteorites brought back by the Apollo astronauts.

  • - Ok. - But we don't have any Martian rocks.

  • - Because we haven't been to Mars. - We haven't been to Mars.

  • - What the Mars rover up to lately?

  • - It is looking at things very much similar to this right now.

  • But, what we do know a lot about is the Martian atmosphere.

  • We know what it's made out of, and what this has inside of it

  • is a sample of the Martian atmosphere.

  • So that could be extracted and is an exact match to the Martian atmosphere.

  • - So it's like a finger print, like atmosph-- - It's a fingerprint.

  • Atmospheres have fingerprints.

  • - That's amazing! - CSI Meteorites.

  • - That's amazing! - That's what we do here.

I think this is the only collections tour I've been on where I've been handed gloves.

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スパアエースからの隕石! (Meteorites From Spaaaaaace!)

  • 509 17
    邱鈺馨 に公開 2021 年 01 月 14 日
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