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What is it?

This is a meteorite. It fell to Earth near Chihuahua, Mexico at 1:05am on February 8, 1969. It is known as the Allende Meteorite, named after the nearby village, Pueblito de Allende. It is approximately 3cm x 2cm and weighs 18 grams.

That doesn't seem very big.

You need to remember that our meteorite is part of a much bigger piece of rock. As the meteoroid entered Earth's atmosphere it would have heated to enormous temperatures and exploded into lots of little bits, one of which is our piece. So far around two tonnes of these smaller pieces have been found over an area of about 60 miles. This means that the original rock must have weighed several tonnes.

What is special about the meteorite?

Firstly it is a very rare type of meteorite - a Carbonaceous Chondrite. Only about 3.6% of all meteorites fall into this category.

Secondly it is very old. Chondrules (from which chondrites are formed) are thought to be among the oldest materials in our solar system. Scientists think that they were formed about 4,550 million years ago, when the first solid matter was forming. That makes the meteorite about 700 million years older than the oldest rocks on Earth!

Thirdly, it is possible that the carbon in this meteorite was involved in the start of life.

The carbonaceous chondrites contain amino acids, some of which are not found on Earth. Amino acids are necessary for life. If they exist in places outside the Earth then maybe life also exists on other planets.

Also, if these amino acids have reached the Earth today what is to say that amino acids did not also land on Earth many millions of years ago? Carbonaceous chondrites were more common 4,000 million years ago and their amino acids may have made life on Earth possible. Many people do not think this is likely but it is an interesting theory.

It has also recently been observed that if the amino acids are exposed to high temperatures or extreme shock (like a huge impact) then they are converted to polypeptides - a further step along the road to forming self-replicating organic molecules, i.e. life.

What does the picture show?

This image shows a barred olivine chondrule from the meteorite. The dent may have been caused by a collision while it was still molten (melted). This may be one of the earliest collisions on record - it probably happened over 4,556 million years ago. Another theory is that the chondrule was spinning very quickly and a blob of heavier material was spun to the surface and thrown out.

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