Scientists are warning that we need to start blasting asteroids before they collide with Earth - the latest threat being asteroid 1999 RQ36 - set to hit the Earth in 50 years.

The asteroid is more than half-a-kilometre wide is heading for the Earth - and we've got just 50 years to knock it off course.

The asteroid was discovered in 1999 and is most likely to hit us in 2182, study co-author Maria Eugenia Sansaturio said.

It has a one in 1000 chance of striking Earth, but it's not an exact science.

"The consequence of this complex dynamic is not just the likelihood of a comparatively large impact, but also that a realistic deflection procedure (path deviation) could only be made before the impact in 2080, and more easily, before 2060," News.com.au quoted Sansaturio as saying.

"If this object had been discovered after 2080, the deflection would require a technology that is not currently available."

Scientists insist that it would be prudent to blast the thing away while we still can.

"This example suggests that impact monitoring, which up to date does not cover more than 80 or 100 years, may need to encompass more than one century," she said. (ANI)