65 million years ago, the dinosaurs were wiped out by at least two meteorite impacts, rather than one single hit, new research has found.

Before the new study, scientists had identified a large impact crater in the Gulf of Mexico as the event that ended the reign of the dinosaurs.

Evidence for a second impact in the Ukraine has been found.

This raises the possibility that the Earth may have been bombarded by a shower of meteorites.

The new study is being published in the journal Geology by team lead Professor David Jolley of Aberdeen University.

When it was first proposed in 1980, the concept of a meteorite impact killing the dinosaurs was a hugely controversial. However, the discovery of the Chicxulub Crater in the Gulf of Mexico, was hailed as “the smoking gun” in the now confirmed theory.

The discovery of a second impact crater suggests that the dinosaurs were drive to extinction by a “double whammy” rather than a single strike.

In Ukraine, the Boltysh Crater was first found in 2002. However, it was uncertain until now exctly how the timing of the event coincided with the Chicxulub impact.

In the new study, scientists looked at the “pollen and spores” of fossil plants in the layers of mud that filled up the crater. They found that immediately after the impact, ferns colonized the landscape.

Ferns have an incredible ability to bounce back after catastrophe. Layers of fern spores, called “fern spikes”, are considered to be good markers of past impact events.

There was an unexpected discovery for the scientists, however.

They found another “fern spike” an a layer about 4 feet above the first, suggesting that another impact event happened later.

Professor Simon Kelley of the Open University, who was co-author on the study, said, "We interpret this second layer as the aftermath of the Chicxulub impact".

This is proof that the Boltysh and Chicxulub impacts did not happen at exactly the same time. They struck several thousand years apart, the length of time between the two “fern spikes”.

Professor Kelley added, “It is quite possible that in the future we will find evidence for more impact events".

Rather than being wiped out by one hit, the researchers think that dinosaurs think that the dinosaurs may have been victim of a meteorite shower raining down over thousands of years.

It is still uncertain what may have caused the bombardment.

Professor Monica Grady, an expert on meteorites at the Open University who was not involved in the study, said, "One possibility might be the collison of Near Earth Objects".

NASA recently launched a program celled “Spaceguard”. It hopes to monitor Near Earth Obhects for an early warning system of possible future collisions.