Astronomy

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Video

Materials

• 1 bowl
• Flour
• Cinnamon powder (or cocoa powder or chocolate milk powder)
• 1 pair of tweezers
• "Meteorites" (for example pebbles, marbles and lumps of clay)

Short explanation

An impact crater is formed when a celestial body hits Earth's surface. What the crater looks like depends on the surface where the impact takes place, and the impacting rock.

Long explanation

The solar system consists not only of planets, dwarf planets and moons, but also of a lot of smaller celestial bodies that go under the collective name Small solar system bodies (SSSBs). These includes comets, asteroids and meteoroids, all of which can collide with Earth. Comets and asteroids are large celestial bodies, from around 10 m (30 feet) to several miles (kilometers) in diameter, which can cause mass extinction on Earth. Meteoroids are usually less than 10 m (30 feet) in diameter, but even these can cause some damage to Earth.

Meteoroids are so small that they are normally only detected when they enter Earth's atmosphere. They are then rapidly heated by the friction that arises (collisions between the particles the atmosphere consists of and the meteoroid) and evaporate completely or partially while emitting a strong glow. This celestial phenomenon is called a meteor. If part of the meteoroid reaches the ground, the resulting rock is called a meteorite.

Astronomers are better at monitoring comets and asteroids, at least the large ones. But at any time, you may hear the news that Earth will be hit by a devastating asteroid or comet. Many are still hidden in the darkness of space.

In the event of an impact, an impact crater is formed. An SSSB usually hits Earth at an extremely high speed, several tens of kilometers (miles) per second. This means that the rock is actually most often completely destroyed at impact, in a large bomb-like explosion. Only the crater remains, which tells future visitors about what happened. Due to the explosion, the crater usually becomes round, even if the celestial body hits Earth's surface at an angle. Only at really narrow angles of incidence do elongated craters form.

The Moon is famously covered by impact craters, most of which were formed in the early history of the solar system when many more SSSBs whizzed around among the planets and moons. Earth would actually have the same scarred surface as the Moon, if it wasn't for erosion, weathering and continental drift constantly smoothing out Earth's surface again.

In this model, flour is used to resemble Earth's bedrock. The cinnamon is used to make it easier to see what happened during the impact. You can also pretend the cinnamon is Earth's top rock layer - the crust.

Experiment

You can turn this model and demonstration into an experiment. This will make it a better science project. To do that, try answering one of the following questions. The answer to the question will be your hypothesis. Then test the hypothesis by doing the experiment.

• What happens if you change the mass of the meteorite?
• What happens if you change the size of the meteorite?
• What happens if you change the speed of the meteorite?
• What happens if you change the angle of incidence?
• What happens if you change the surface to something else than wheat flour (for example sand, potato flour or corn flour)?

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