The Earth experienced a massive bombardment from meteoroids 480 million years ago after the break-up of a giant space rock.

The amount of material that rained down on our planet was 100 times that experienced today, say researchers.

The evidence comes from fossil meteorite fragments found in limestone deposits spread over a wide area of Sweden.

These all contain a particular mineral signature that links them to the same mighty asteroid that came apart in a collision with another huge rock.

The research team, from Göteborg University and Rice University, US, reports its findings in the journal Science.

Today, meteorites impact the Earth at a rate of about one per year every 12,500 square kilometres (7,700 square miles).

But the new study found a 100-fold increase in this activity when carbonate rocks were being deposited in what is now Sweden a little under half a billion years ago.

The researchers investigated more than 40 meteorite fossils caught in these limestones at quarries spread over a 250,000-sq-km (150,000-square-mile) search area.

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