Meteorite Loan Box 1: What are meteorites?
The Earth is constantly bombarded by material from space. Fortunately, most of this falls as tiny grains which burn up completely as they pass through the atmosphere and are seen as meteors ("shooting stars").
However, the few rocks from space which survive the journey through the atmosphere and land on the Earth's surface are called meteorites.
Some meteorites are similar to igneous rocks on Earth, others are pieces of metal, and others are unlike anything seen on Earth. Almost all meteorites are fragments from asteroids and have the same age as the solar system; approximately 4.5 billion years. They contain important evidence which helps us construct theories about the origin and history of our solar system.
Included in Box 1:
1. Indochinite tektite
Sometimes meteorite impacts melt the Earth's crust and splatter the ground with droplets of rock glass. They are called tektites.
2. Chondrite meteorite
Chondrites are made of small spheres (chondrules) that clumped together in the early solar system. The Earth would have originally formed from material like this.
3. Nickel iron meteorite
This meteorite fell on February 12, 1947 in Russia. This is the core of an asteroid, which has a similar composition to the Earth's core.
This is another form of tektite, but looks like green glass. It is formed from rocks, melted by an impact, which cooled while they were airborne and preserved their ‘droplet shapes’ on landing.
5. Carbonaceous chondrite
This meteorite is an example of the oldest material ever found — 4.56 Billion yrs old! It is also the most-studied meteorite in history.
6. Iron Octahedrite, showing Widmanstatten texture
The beautiful structure in this meteorite is caused by the growth of two alloys of iron and nickel. When polished and acid etched a ‘Widmanstatten pattern’ of crystals is visible.
Pallasites are a rare type of meteorite. They are thought to have come from the core/mantle boundary of large asteroids.
Achondrites are stony meteorites which are made of material similar to Earth basalts. This one comes from the crust of asteroid 4 Vesta.
9. Iron Octahedrite from Meteor Crater, Arizona
This Meteor Crater in Arizona is the best known impact crater on Earth. It is about 50,000 years old. Many small fragments of this meteorite have been found around the crater.