Scientists warn of danger from rogue 60

While Nasa focuses on asteroid threats, new research suggests they need to also look beyond the orbit of Jupiter, where the distant comets are lurking.

A comet strike may have wiped out the dinosaurs, and a repeat incident would mean major devastation for Earth.

Hundreds of these massive comets, called 'centaurs,' have been discovered over the last two decades.

Centaurs are balls of ice and dust, with an unstable orbit that starts beyond Neptune. 

They can reach sizes of 31 to 61 miles wide. A single centaur contains more mass than the entire population of Earth-crossing asteroids discovered to date.

In their orbit, these comets will cross paths with Jupiter, Saturn, Uranus, and Neptune. 

Occasionally, a comet will ricochet off the gravity fields of one of these large giant planets, sending it hurtling towards Earth.

This, the researchers say, happens once about every 40,000-100,000 years.

As the comets get closer to the sun, they begin to disintegrate, breaking up into debris tails and 'making impacts on our planet inevitable.'

Most studies examine the 'extraterrestrial impact' of objects in the asteroid belt, which lies between mars and Jupiter. 

The researchers argue that focusing on near-Earth asteroids underestimates the nature and magnitude of potential giant comet strikes.

'In the last three decades, we have invested a lot of effort in tracking and analysing the risk of a collision between the Earth and an asteroid,' said co-author Bill Napier of the University of Buckingham.

'Our work suggests we need to look beyond our immediate neighbourhood too, and look out beyond the orbit of Jupiter to find centaurs. 

If we are right, then these distant comets could be a serious hazard, and it's time to understand them better.'

First life on Earth may have been sparked by comet bombardment, which brought water and organic molecules. 

Many scientists also believe a comet may have brought about the extinction of the dinosaurs 65 million years ago.

'A centaur arrival carries the risk of injecting, into the atmosphere…a mass of dust and smoke comparable to that assumed in the nuclear winter studies,' the researchers wrote.

'In terms of magnitude, its ranking among natural existential risks appears to be high.'

While the risks from a centaur comet are not 'known to be imminent,' according to the researchers, the team says these types of encounters are unpredictable. 

Nasa tracks around 12,992 near-Earth objects which have been discovered orbiting within our solar system close to our own orbit.

It estimates around 1,607 are classified as Potentially Hazardous Asteroids.

The latest research suggests several hundred more Centaurs should be added to the list of space rocks that threaten Earth. 

(dailystar.co.uk)