Building blocks of life can spring into existence spontaneously when icy comets smash into planets, a study has shown.

A similar process can create amino acids - bits of proteins - when a rocky meteorite hits an ice-covered world. The discovery suggests life could be getting a kick start just about everywhere in the universe.

How often the building blocks end up constructing proteins and living organisms is an unanswered question. But the research fills in another piece of the puzzle of life's origins on Earth.

Scientists believe at the time life first emerged, between 4.5 and 3.8 billion years ago, Earth was hit by comets and meteorites.

Dr Zita Martins, from the Department of Earth Science and Engineering at Imperial College London, said: "Our work shows that the basic building blocks of life can be assembled anywhere in the Solar System and perhaps beyond. However, the catch is that these building blocks need the right conditions in order for life to flourish.

"Excitingly, our study widens the scope for where these important ingredients may be formed in the Solar System and adds another piece to the puzzle of how life on our planet took root."

Proteins, the giant molecules that form living tissue, are made from chains of amino acids whose assembly is directed by genetic code.

Writing in the journal Nature Geoscience, the scientists show how when a comet - essentially a dirty snowball - impacts it creates a shock wave that generates the molecules needed for amino acids.