We see one.
We see the Asteroid Vesta, which is about 500 kilometers in diameter.
And it is the only asteroid that we know,
it's actually been visited by a spacecraft recently.
So we know this for sure, but we were pretty sure of this before.
It's nearly circular, it's got a big sort of impact crater on the south,
makes it look a little bit funny, but we're very certain it is differentiated.
It has an iron core on the inside, and we are dead certain that it was melted
because we see molten material that has flown on the outside.
We see the salt.
The salt is that left over product from a magmatic flow.
The salt is the stuff that makes the Hawaiian Islands that dark rock.
It's the stuff that's on the mare of the moon that lets us know that the moon had
volcanoes that was spewing out on a surface.
That's to has basaltic material that is flown and covered much of the surface.
We know that its interior was molten.
We know that it has an iron core.
So are the iron meteorites from Vesta?
Well, no, because you would have to crack Vesta open to find that iron core.
Vesta's clearly never been cracked up and
although, when impact tried very hard to do it.
In fact, you could see that really big impact based on at the south pole of Vesta
from this beautiful dawn image.
You see sort of these thing here on the middle, but
that's actually the mountain in the middle of the crater.
The crater takes up almost the entire South Pole, and it's from this crater
where all these meteorites have been delivered to the Earth.
You can see another consequence of this really massive impact.
If you look at Vesta from the side, now, the South Pole is down here.
And that impact was so large and so close to almost breaking the entire body apart,
that you get these striations along the equator where you had compression as this
thing slammed into the bottom down there.
There are some asteroids, they're called M class asteroids.
We'll talk about the classes of asteroids a little bit later.
M class asteroids look like they are just remnants of iron core.
They are just total chunks of iron.
And you can actually tell they're iron by using radar to reflect off of them.
As you can imagine, a big chunk of iron is very reflective in radar.
And sure enough, they're just chunks of iron.
And they presumably started out as larger mini-planets.
Not as big as I'm drawing relative to the Earth here.
So I should draw these all really small, like, to expect to,
I want to give you the idea.
That impact stripped the mantle material away from them, and
left just this raw iron core leftover.
What does a metallic asteroid look like?
I don't know, but we're going to find out.
Maybe it looks like this.
NASA is sending a probe to an asteroid called Psyche.
And Psyche is also the name of the spacecraft just to make things confusing.
But it might look like this, it might have strange craters,
it might have weird land forms.
I can tell you, it will be nothing we've ever seen before, I can't wait.
You can imagine this process also happened that would have shattered the iron core.
When the iron cores get shattered, chunks of iron flow off into space,
some of which eventually land on the earth.
I love holding this little piece of iron meteorite in my hand, and showing it to
people, and explaining to them that this is the core of a tiny, mini-planet.
That was forming back at the very beginning of the solar system, that sadly,
had an impact which catastrophically shattered it into pieces, but
then let parts of it fall onto the Earth.
It's a cute story.
Is it really true?
Well, there are just so many aspects of it that make the story so incredibly true.
Let me show you my favorite picture,
this time though, of my favorite type of meteorite.
I have to show you a picture because these are so cool that they're very expensive,
and I don't have one.
I would love to have one.
If anybody has one in their collection, they'd like to send it to me, please do.
Here's what the pictures look like.
This is called a Pallasite, and this one is a beautiful, polished up one.
And what do you see? Well, this stuff,
it's hard to tell because it's reflecting, this is iron.
This is essentially an iron meteorite, this material in through here.
And this, these are crystals of olivine, pyroxene.
These are the crystals that we find inside the mantle of the Earth.
Where would you get iron and olivine next to each other?
Well, you would find it in one place.
It's actually, you wouldn't quite find it on the Earth.
But you would find it in, if you had an iron core and
you had a kind of small planet,
you would have at the core mantle boundary right there, you would have olivine.
This would be olivine in here, maybe pyroxene too.
And you would have that right on the core mantle boundary.
If you shattered that little planet to pieces, there would be some of these
places where the iron had where the iron and the olivine were still mixing.
This is, this represents an incredibly special spot in the solar system.
In the, right at the core mantle boundary of some mini-planet that was
just forming at the beginning of the solar system before it got smashed apart.
We will never see the earth's core mantle boundary or any other planet.
But here we have, this person is holding,
in his hands, the core mantle boundary of this little mini-planet.
It's just an astounding thing.
This is officially an achondrite, because it's not chondritic, but it's not iron.
Or maybe this one is called a stone in the iron because it has stone and iron.
But you can find things that are pure achondrites which are from these parts,
from the mantel parts, or maybe even the crust parts, those would be achondrites.
They don't have chondrites anymore because the melting that happened
would have melted the chondrites.
And they would have just then turned into whatever the materials here, well,
olivine, pyroxenes, whatever is on the surface, these things.
We find achondrites that came from Vesta, the asteroid that I just showed you
of those basaltic parts that come from the top.
We find other achondrites,
some of them have now been associated with coming from the surface of Mars.
And we can tell, by their compositions,
that they match precisely the composition of Mars, they're at the surface of Mars.
We find achondrites on the surface of the Moon, quite an astounding thing.
We can get lunar samples by just sitting here waiting for
them to fall down, pretty cool.
All of these things tell you, again, of this incredible and
dynamic period very early in the solar system,
where things are melting, things are forming into little mini-planets.
Things are being shattered to pieces, reaccumulating.
Some of them were melting, some of them are not.
The fact that these are maybe 10 kilometers across or
100 kilometers across.
And yet, we also have asteroids that are those sizes is sort of a surprising
things, chondrites.
Why did some things melt?
Why did some things not melt?