Physics Applications:
Introduction to Gravity

The Slingshot

Kepler's Laws

Newton's Laws

Types of Orbits

Lab: Crater's Diameter

Lab: Probability of Asteroid striking



Meteroid Topics covered on this page:

What are Meteoroids, Meteors and Meteorites?

There are three stages to the phenomenon regarding meteors. In the majority of the cases, an object will only make it to the second stage. Here are the stages:

Meteoroid: A piece of debris that is traveling through space towards our planet.

Meteor: A brief flash of light that we see at night which is not caused by the material "burning" with friction from the atmosphere, but instead, from the excited atoms caused by the object's high speed.

Meteorite: A small number of objects that are not entirely destroyed in the upper atmosphere and arrives at the ground.

Great balls of fire!

House Pieces of material which cause meteors to enter Earth's upper atmosphere at very high velocity: around 260000km/h. The flash of light that we see happens when the object is around 100 km above the surface of the Earth. If the object were to be the size of a grape, than it would create a brilliant flash that could even cast shadows on the ground. Such bright meteors are called FIREBALLS. The image here shows a fireball.

The origins of meteor showers

Many more meteors can be seen at night during a certain time of the year. The reasons behind this are comets.

A falling star As a comet orbits near the Sun, it loses materials, such as dust and rocks, which are given out by the tail. These materials cause a continuous trail to form behind the comet as it orbits. When the Earth crosses the path which a trail once was, the particles of materials that they contain are taken up by Earth's atmosphere. These appear in the sky as a shower of meteors. The dates of these meteor showers are known. For example: The Eta Aquarid shower (around May 4th) and the Orionid shower (October 20th) are both cause by the trail left by Halley's comet.

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All about meteorites...

The vast majority of the meteors are from comet trails, however, these particles are usually too small to survive the trip to the Earth since they burn up too quickly. On the other hand, much larger chunks do survive. These meteorites are from a different source though. Rather than a result from the trail left by a comet, meteorites are originated from asteroids. When colliding with another asteroid, pieces or chunks will break off, and in other cases, the entire asteroid might even be shattered. The result is a cloud of RUBBLE, which are large pieces of rock and metals from the original asteroid that wander into the path of the Earth and fall through the Earth's atmosphere.

The resulting meteor is incredibly bright and could even cast strong shadows. Even though a whole lot of the meteor is burned off, some may still survive, and the resulting meteorite gives plenty of information about an asteroid's composition and even that of the early solar system.

This meteorite fell on Earth on August 14th, 1992 in Uganda. The meteorite was made of stone, which broke down along its fall causing debris to be distributed over an area of 3 x 7 km. At least 48 fragments have been found, and it is thought that the original object might have been 1000 kg. The largest piece recovered is shown in the picture.

Even though most meteorites come from asteroids, there are some that are thought to have come from comets, and other that have a composition, which is relatively close to the rocks found on the Moon. At least 7 other meteorites are of a type that match closely to the materials found on Mars, which suggests that there was probably an impact on the surface of Mars. A Martian meteorite is shown here.

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Meteorites are generally divided into three classes according to their composition:

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Impacts on Earth

Property Damage We are very lucky today that the majority of debris, which enters Earth from space, is small in size. However, a small fraction of the pieces do survive the journey. These are meteorites, as we have discussed in the previous section. Meteorites usually cause not too severe damage than a hole in a house roof or a small crater in the ground.

Earthly impacts On the other hand, things were not always this fortunate. During the past, Earth has been hit by much larger objects, which have left scars on the surface. For example, some scientists believe that the disappearance of the Dinosaurs about 65 million years ago was caused by the impact of a large asteroid in an area now covered by the Indian Ocean. Some also believe that a huge body (possibly the size of a planet) caused a large piece to fracture off our planet and form the Moon, which we see today. Here are several impact sites on Earth that we have been able to identify.

Here are some famous craters from around the world:

Arizona Barringer, Arizona, USA.

Barringer is 1.2 km across, and is about 49,000 years old. It is possibly the most famous terrestrial impact crater,

Australia Wolfe Creek, Western Australia.

This crater is less than 0.3 million years old and has a diameter of 0.9 km.

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Langstaff Secondary School Independent Study Unit

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