Simulating Meteor Strikes
Sun, 10th Dec 2006
Part of the show Dark Matter, Life on Mars and Galactic Collisions
What you Need
A tray, like a cooking tray, or a shallow pan
A few hundred grams of flour
A fine powder that's a different colour to the flour (we've used cocoa but custard power might do)
Small round things around the size of maltesers!
What to do
1 - Lay at least an inch of flour into the tray. You don't want to make it too compressed, so perhaps use a sieve. Mix it up to get some air in there.
2 - Sieve some cocoa powder onto the surface of the flour. This will allow you to see what's happening. The cocoa will act like the topsoil on the earth.
3 - Use the maltesers as meteorites. Drop them in from directly above and then from various angles to see what effect that has!
What may happen
Why does it happen?
The malteser ended up deep down into the flour, and the flour has been thrown up on top, covering the cocoa powder in a circle of about 5cm in diameter. When you drop the malteser, it's gaining kinetic energy as it falls towards the earth, just as a meteorite would do. When it actually hits, all that energy has got to go somewhere. In a real meteorite some of that would become sound, and heat (which melts things), but lots of it just goes into throwing stuff around.
So why is it that the earth from underneath the meteor gets thrown up to the edge of the crater?
Well the cocoa, or the earth's surface, will get thrown around as well. But so much more of the deep stuff gets thrown up that it will cover the surface around the edge of the crater. This will also tend to lift the edge of the crater, which is why they tend to have those high rims.
So what about a meteor that strikes on an angle?
Well now all the flour that is thrown up by the malteser meteor spreads out further, and only in the direction which the meteor was flying in.Because the malteser has a lot of momentum in one direction, it will tend to transfer that momentum into the earth which is being thrown up.
How is our experiment similar to an actual meteor hitting the earth?
It's a very similar set up. A meteor hitting the earth will tend to vaporise things and throw them around. Most of it will be within a kilometre or two but some of it can spread thousands of miles up into the stratosphere. Normally craters are circular, because the size of the meteorite compared to the size of the crater is tiny. Meteors fly through our atmosphere at around Mach 25 (25 times faster than the speed of sound - about 20 thousand miles per hour) which means they have an immense amount of energy. When they hit the ground it's like a nuclear bomb going off. A famous meteor crater in Arizona was created when a 50 meter across Asteroid hit the earth. The crater it left behind is about 1.2 kms across. That's like 2.2 million tonnes of TNT going off all at once!
For Gemma to simulate that, she'd have to throw that malteser incredibly hard! Of course, you'd also get an awful lot of mess.