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Hello, comments and asteroids used to be regarded as the vermin of the solar system, irritating

rubble that got in the way of astronomers trying to study more interesting phenomena.

It was difficult or even impossible for an observer of

asteroids to book time using the world's best telescopes because they were

regarded as unspectacular objects that could tell us little about the origins of

the universe. However, this has changed.

It's now thought that asteroids are the unused building blocks of planets,

pristine material that has remained chemically unchanged

since the creation of the solar system. A snapshot of matter at the beginning of time.

At the present moment, the Japanese probe Hayabusa is 180 million miles away, pinned to the back of the asteroid Itokawa attempting to gain our first

samples of the chemical composition of an asteroid.

Why did asteroids fail to form planets?

How do they differ from their celestial cousins the comets and are either

of them likely to create another impact on planet Earth? With me to discuss asteroids

and Monica Grady, Professor of Planetary and Space Sciences at the Open University.

Carolyn Crawford, Roys Society Research Fellow at the University of Cambridge

and John Zanneki, Professor of Space Science at the Open University.

Monica Grady, Asteroids were discovered in the 18th century

when they were looking for something else. Can you tell us about how the asteroid belt was

discovered? Yes, Boad's law was, well it was Titius Bode and also by Kepler, understood or was studying

...