Washington, Nov 18 (IANS): A new NASA map has revealed that over 556 asteroids smashed into the atmosphere over a 20-year period between 1994 and 2013, suggesting that space rocks are slamming into the Earth's atmosphere at a higher rate than previously thought.

Most space rocks were, however, harmless and disintegrated when they hit the atmosphere.

The orange dots on the map, prepared by NASA's Near-Earth Object Programme, show the frequency of asteroids that hit locations during the day while the blue dots show those that hit at night, CNN reported.

But not all asteroids disappeared into the air.

On Feb 15 last year, a 55-feet long asteroid crashed in the Urals region in Russia - largest to hit the Earth during the mapping period, the US space agency said.

The fiery explosion injured over 1,000 people and caused an estimated $33 million in damage.

“The new data could help scientists better refine estimates of the distribution of the sizes of asteroids to protect our home planet,” NASA scientists added.

The US space agency is also working on an Asteroid Redirect Mission (ARM) to redirect a space rock into orbit around the moon.