Biolf not by comets.

 For over a century, it has been thought

that t h e f u n d a m e n t a l ingredients that

fuelled the evolution of life may have

been brought to our planet by comets,

raining down vital chemicals as they

bombarded the young Earth.

A study led by Cambridge scientists

has cast serious doubt on this theory,

with results that "challenge the long-

held assumption".

In the first 500 million years after the

formation of the Earth, our planet is

likely to have been struck by more than

100,000 comets of over 100m in diame-

ter during a chaotic period of regular

bombardments from stray space rocks

hurtling around the young solar system.

Although comets are known to

contain large concentrations of organic

molecules, most of these are likely to

have been destroyed during their fiery

impacts on planet, making

"exceedingly rare" that these life-giving

chemicals were successfully delivered

to the Earth's surface, the study said.

Though cyanide is synonymous with

poison in many people's minds, hydro