Int US 3508 Folder Collection
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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 the— you'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 types— the 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.
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Meteorites From Spaaaaaace!

3508 Folder Collection
邱鈺馨 published on June 21, 2015
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