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Listen to ExperimentMargarine Planets
Use a tub of ordinary margarine to model how a planet forms, and to explain why we get different types of meteorite.
What you need
| Margarine - the simpler the better. (I used baking margarine). |
| Small glass or jar |
| Microwave |
What to Do
Put a few lumps of margarine into a small microwave-safe glass or jar.
Heat it up gently in the microwave, until the margarine melts. This will happen a lot faster than you expect, and then it will boil quite violently.
Very carefully take the margarine out, as it may be very hot.
Leave it to stand for 1-2 minutes
What may Happen
Once the molten margarine is left to stand, it separates out into two sections, a yellow upper layer, and a transparent lower layer.
What is going on?
Margarine is made from vegetable fat and water. They are mixed up together incredibly well, and the fat is cool enough to congeal, and go fairly solid. When you heat it up, the fat melts, allowing the small droplets of water to move around. Water is denser than fat, so it sinks to the bottom of the container, forming two separate liquids.
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Margarine is made of fat with some lumps of water inside. | If you melt the fat, the water sinks. | This leaves a layer of water at the bottom, with oil above |
You can do the same thing with butter, but the water has a lot more things dissoved in it, and it is a lot less distinct from the butter-fat layer. (In fact, when you clarify butter in cooking, you are collecting just the butterfat, without the liquid, which is relatively clear).
What has this got to do with planets?
The planets were formed early in the solar system's history, out of a protoplanetary disk. The substances which solidified quickly, and don't evaporate, formed small lumps which slowly accumulated into larger bodies. Some of these melted, and the denser materials sank to the centre, under gravity, forming metallic cores.
| The rocky inner planets and the asteroids are all made of the materials at start of the solar system, which condensed easily. (Mostly silicate minerals, with various metals and sulphites mixed in). |
| When a body accumulated, a huge amount of energy was released from all the collisions. This melted the larger bodies. If they were large enough to produce significant amounts of gravity, the denser materials sank towards the centre. |
| Eventually this meant that a dense metallic core formed, with a less dense stony outer layer. |
| On very large objects, like the earth, with more gravity, and which have stayed molten for longer, more layers formed. (Such as the continental crust, which is less dense than the rocky mantle). |
This basic separation took place even in large asteroids, some of which are thought to have been destroyed by monumental collisions in the early solar system. Some of the fragments rain down onto the earth in the form of meteorites. As there are different layers in a large asteroid, there are different types of meteorite.
| Chodritic meteorites are thought to be made up of the original stuff of the solar system. They contain tiny balls called chondrules, which appear to have been molten in free space. |
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| Rocky meteorites are made up of the outer layers of asteroids, and sometimes planets. Some can be shown to come from the moon, and Mars. |
| Iron meteorites are made up of an alloy of iron and nickel, and were once part of the core of a large asteroid, or planetoid. |
Written by Dave Ansell
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