Scientists say an asteroid about the size of a football field hurling through space came close to colliding with Earth last week. The object could have caused significant loss of life if it had struck the planet.
It was one of the closest near-misses between Earth and an object of this size ever recorded. In fact, scientists say the path of the asteroid brought it within 125,000 kilometers of Earth, less than a third of the distance to the moon.
Grant Stokes, part of the team of scientists at the Lincoln Near Earth Asteroid Research Project whose New Mexico telescope discovered the asteroid, said "that was a very, very close pass."
This asteroid was not spotted until three days after it raced past Earth at a speed of more than 37,000 kilometers per hour. If it had hit the planet, scientists say the energy released on impact would have equaled a large nuclear bomb, capable of causing significant loss of life and scattering debris through the atmosphere.
"Objects in that size range could be expected to hit the Earth on an average of once every century or few centuries. This one would have been a problem if you were under it when it came in but most of the rest of the world, other than perhaps getting some pretty sunsets probably would not have noticed it too much," said Mr. Stokes.
Scientists suspect an asteroid smashing into Mexico's Yucatan Peninsula millions of years ago caused a huge dust cloud that triggered climatic changes and led to the extinction of the dinosaurs. Brian Marsden of the Harvard-Smithsonian Center for Astrophysics warned there may be many more still undiscovered asteroids heading toward Earth. "There must be a million objects of this size that can come close to the Earth and we've discovered only a handful of objects this small," he said.
In fact, you only need to go back as far as 1908, when a huge asteroid smashed into Siberia, flattening hundreds of hectares of forest. The U.S. space agency NASA has begun searching the heavens for any asteroids larger than a kilometer in size that could be on a trajectory toward Earth. What, if anything, the world could do to avoid a collision with one large enough to threaten life is far from certain.