[MUSIC] >> What you're looking at here is the biggest meteorite slice in the world. It's a 550-kilo slab of the meteorite Agpalilik, which was found in 1963 in Northern Greenland. The picture here shows the meteorite and you can see the cut surface from where the slab was cut. Next to the meteorite you see Vagn Buchwald who found the meteorite in 1964 and who also wrote a 2,500 page book describing every iron meteorite known on this planet. But getting back to the meteorite, look at this pattern that you see all across the surface. It's a crystal structure that formed when the iron core of the asteroid from which this one came crystallized 4.5 billion years ago. When we look at the crystals, we can see how slowly the core cooled, and it turns out to be about 30 degrees per million year. And therefore, it's impossible to duplicate this. We can't make fake iron meteorites, because it would take much too long. We don't have the time to cool so slowly. [COUGH] We think that these crystals could actually be kilometer sized. And that's a safe prediction because we don't have any meteorites that are kilometer sized that could potentially prove me wrong. But at least meter sized. Iron meteorites are single crystals. It's the same crystal pattern that we see all across the surface. The other interesting things we see here, we see these elongated star inclusions. It's actually troilite, It's an iron sulphite. And in fact, it's sort of sausage-shaped, if we could pull them out of the meteorite. The reason why they're here is that when this core crystallized and the sulfur could not fit into the metal structure. It's a bit like if you freeze salt water, everyone knows that salt and water, and water ice is a bad combination. So, if you freeze water ice, the salt will concentrate the remaining liquid, which will get more and more salty, and you have to cool to lower and lower temperatures to make it freeze. Same thing here, the sulfur concentrated in the last remaining liquid. So these elongated features are the last portions of the melt that remained. If we look at it in great detail, like up here, we can see at the top here there are some tiny crystals that have collected at the top of this inclusion that was once liquid after the metal had crystallized. These inclusions turned out to be chromites, little crystals that are a little bit more heavy than the liquid here, which actually shows you that we've been cheating a bit. This meteorite is upside down. The little asteroid had its own gravity field, of course pointed towards its center. And the center of the asteroid was in this direction. The core was only ten kilometers, maybe, across. So this is just a little tiny fragment. So the reason, why do we have this meteorite here, it's quite clear that when I have a piece of an asteroid core here at the museum, obviously the asteroid could not be in a very good shape. This asteroid collided with another asteroid some 650 million years ago, and the fragments from the collision are still raining down on the Earth. It's the most common type of iron meteorite hitting the Earth today. We have 300 pieces from the collision that has hit the Earth within the last few thousand years, and they keep coming. So piecing all this together we can understand how the core of this particular asteroid crystallized. We can use the cooling rates to determine how big it was, and thus we construct its history, how it formed 4.5 million years ago, and what the subsequent evolution was that resulted in us having a piece of the core here at the museum today. [MUSIC]