Stones from the sky

Meteorites are rocks that arrive on the Earth’s surface from interplanetary space. Most are fragments of debris from the asteroid belt, but some, much rarer, meteorites are from the Moon and even Mars. These are smashed away during impacts with other bodies. Then they drift through space for thousands or even millions of years before encountering another body—perhaps the Earth.

One way to identify a meteorite is by its black glassy coating, called a ‘fusion crust.’ It forms through the frictional effect of the atmosphere on the rock’s surface. Most meteorites are only discovered many years after they've fallen. The best places to find them are hot and cold deserts, such as the Sahara, the Nullarbor Plain in Australia and the Antarctic ice sheet. They’re easily spotted against sand or ice, but if a meteorite has been on the Earth for some time, it will look weathered and annoyingly just like a plain old Earth rock.

There are three types of meteorites: irons, stony-irons and stones. Irons are made up almost entirely of iron-nickel metal. Stony-irons are an equal mixture of iron-nickel metal and rocky material. Stones are made entirely of rocky material and look very much like Earth rocks.

One type of stony meteorite, the carbonaceous chondrites, are very intriguing because they contain traces of carbon-based organic molecules, such as amino acids, sugars and hydrocarbons. These molecules are similar to those found in living things, so they're very important if we want to unravel how life on Earth—or elsewhere in the universe—may have arisen. Scientists across the UK (for instance, at the Planetary and Space Sciences Research Institute at The Open University and the Natural History Museum in London) are working to solve these profoundly important puzzles.

Click on the link below to find out more at the Open University's Astonomy Research

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