Quote Originally Posted by Gatekeeper777
they have allread worked out the numbers to avoid a collsion. they need at minimum 5 years notics. in otherwords at the curent point in time its immpossible cuz most times we only have a month if we are lucky.
An object the size of mars unlikely but the object to hit earth ond kill off the dinosaurse was only expected to be 1 km and you know there are thousands of them. as well as hundreds of long orbiting and short earth crossing comets and astroids.

On July 9, 2002, MIT astronomers discovered 2002 NT7, a 2 km-wide space rock in a curious orbit. Unlike most asteroids, which circle the Sun in the plane of the planets, 2002 NT7 follows a path that is tilted 42 degrees. It spends most of its time far above or below the rest of the solar system. Every 2.29 years, however, the asteroid plunges through the inner solar system not far from Earth's orbit.

After a week of follow-up observations, researchers did some calculations. There was a chance, they concluded, that 2002 NT7 might hit our planet on February 1, 2019. The odds of impact: 1-in-250,000.

also see..
News Article: 1997XF11 and its possible hazard to the Earth.
Even worse is apophis, it is going to have a 1 in 45,000 chance of hitting earth in 2029
99942 Apophis - Wikipedia, the free encyclopedia
Impact event - Wikipedia, the free encyclopedia