1.7 The Worlds Largest Meteorite Slice – Henning Haack

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来自 University of Copenhagen 的课程

起源：宇宙、太阳系、地球和生命的形成

364 个评分

University of Copenhagen

起源：宇宙、太阳系、地球和生命的形成

364 个评分

The Origins course tracks the origin of all things – from the Big Bang to the origin of the Solar System and the Earth. The course follows the evolution of life on our planet through deep geological time to present life forms.

从本节课中

Origin of the Elements, the Solar System and the Planets

In the first module of Origins Jim Connelly and Henning Haack go through the evolution that resulted in the Solar System with the planets that we know today. Jim will tell you about how the elements of the periodic table were formed. Without these elements there would be no Solar System, no planets and no life at all. We have added a couple of more videos that we hope you will also find interesting. One gives you an introduction to Geological time. Videos 1.7-1.9 deals with some of our most interesting meteorites from the collections at the Natural History Museum of Denmark. Much of the evidence for the theories presented in Module 1 has been obtained from meteorites.

1.1 Nucleosynthesis: the origin of elements in our Solar System - Part 1 – Jim Connelly11:35

1.2 Nucleosynthesis: the origin of elements in our Solar System - Part 2 – Jim Connelly9:56

1.3 Origin of the Elements, the Solar System and the Planets - Origin of the Solar System – Henning Haack9:29

1.4 Origin of the Elements, the Solar System and the Planets - Meteorites – Henning Haack17:17

1.5 Origin of the Elements, the Solar System and the Planets - Mars and the Moon – Henning Haack18:06

1.6 Origin of the Elements, the Solar System and the Planets - Exoplanets – Henning Haack2:55

1.7 The Worlds Largest Meteorite Slice – Henning Haack4:22

1.8 Allende - A World Famous Meteorite – Henning Haack2:48

1.9 Imilac - An Exceptionally Beautiful Meteorite Slice – Henning Haack1:11

与讲师见面

Henning Haack
Associate Professor
Natural History Museum
James Connelly
Professor
Natural History Museum of Denmark
Vivi Vajda
Professor
Department of Geology, Lund University
Jon Fjeldså
Professor, Curator
Thomas Gilbert
Professor
Michael Houmark-Nielsen
Associate Professor
Natural History Museum of Denmark
Bent Erik Kramer Lindow
Curator
Natural History Museum of Denmark
Gilles Guy Roger Cuny
Associate Professor
Natural History Museum of Denmark
Ole Seberg
Associate Professor
Natural History Museum of Denmark
Gitte Petersen
Associate Professor
Natural History Museum of Denmark
Tais Wittchen Dahl
Assistant Professor of Geobiology
Arne Thorshøj Nielsen
Associate Professor
Natural History Museum of Copenhagen
Martin Vinther Sørensen
Associate Professor, Curator
Natural History Museum of Denmark
Svend Stouge
Associate Professor
Natural History Museum of Denmark
Danny Eibye Jacobsen
Associate Professor, Curator
Natural History Museum of Denmark
Jan Audun Rasmussen
Associate Professor
Natural History Museum of Denmark
Emily Catherine Pope
Assistant professor
Natural History Museum of Denmark

[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]

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