GREENBELT, Md. (WJZ) -- It appears Earth has dodged more bullets than expected. Last February's meteor blast over Siberia sent NASA scientists back to their computers.
Alex DeMetrick has more on the worrisome numbers that research has turned up.
The odds of a destructive hit by an asteroid have now increased because smaller asteroids have been added to the equation.
They may only be the bits and pieces of the solar system, but asteroids are a threat to Earth and the life on it.
"Nothing to be frightened about, except if they're in the wrong place," said Dr. James Garvin, NASA Goddard Space Flight Center.
Dr. Garvin is NASA's chief scientist at the Goddard Space Flight Center.
"What we're now realizing is there may be more small ones more frequently than we had anticipated," he said.
A realization that literally hit home last February when a meteorite exploded over Siberia. Suddenly, astronomers were news.
"We are sitting ducks. That was a wake-up call that happened in Russia," a scientist said.
Because it was made up of compacted stones, it exploded high up in an air-burst.
It was still powerful enough to injure 1,600 people. If it had been an iron-nickle asteroid:
"It could have hit the surface at hyper velocity and made a crater," Garvin said.
It prompted NASA to do a quiet tabletop drill, where such a hit on D.C. was predicted to kill 78,000 people. An asteroid smaller than a football field might do it.
NASA used to seek out asteroids 100 feet wide and larger. The rock that hit Siberia was just 62 feet -- smaller asteroids making the odds of a destructive hit four to five times more likely.
The Siberian blast was equivalent of 40 Hiroshima atomic bombs.
"The earlier we get warnings of these, the better we can make civil defense preparedness about them," said Garvin.
NASA plans not only to look for smaller asteroids, but there is a goal to eventually catch one for study and learn the best way to someday redirect them away from a collision course with Earth.
Figuring in those smaller asteroids, the air-burst like the one in Russia has dropped from a possibility of once every 150 years to once in every 30 years.
That low-key tabletop drill that NASA ran after the Siberian explosion also estimated a hit off the Mid-Atlantic coast could possibly generate a tsunami 49 feet high.
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