April 2008 – Meteorites

Meeting with Paul Schofield who is working on a project investigating the decontamination of soil affected by metals from mining and industrial sites. Today he is looking at a fragment of meteorite as it many structural similarieties with the rocks here on earth.

The image on the right is a fragment from the Santa Catherina iron meteorite which fell to earth in Brazil between 10,000 and 40,000 years ago.

A meteorite is a fragment which has broken off an asteroid, a body which was formed at the same time as earth, also having a rocky surface and an iron nickel core with a molten layer around it. An iron meteorite is a piece from the core of the asteriod and can give insights into the secrets of our own planet’s core. A piece from the rocky surface would be known as a stony meteorite.

As the molten iron nickel in the asteroid cools and solidifies different patterns of the various metal compounds are formed, each pattern unique to the temperature, pressure, rate of cooling and the oxygen present at the time. In time, rust (iron oxide) is formed on the surface of the meteorite, this too can give an indication of the various compounds that exist underneath the rust. The patterns formed by these compounds during this cooling process are known as phases.

Following this discussion, I feel I would like to learn more about the work being done in this area. So I arrange to meet Caroline Smith who is the curator of meteorites at the Natural History Museum. These images are of some of the stoney and iron meteorites she showed me. The green material in the meteorite shown right is gem quality olivine otherwise known as peridot a semiprecious gem used extensively in jewellery.

The small white mineral grains that can be seen in the stony meteorite bottom left contain calcium and aluminium. They have been used to date our solar system.

I am fascinated by the age and the distances these meteorites have travelled. The cinema has portrayed them as huge pieces of rock that are potentially going to destroy the earth. How does this compare with the tiny crystals I have seen here in different formations and the iron compounds that I know are inside our bodies?

Many thanks to Caroline Smith and the NHS for their help. For more information, visit
Natural History Museum

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