WASHINGTON (AP) — Scientists studying the terrifying meteor that exploded without warning over a Russian city last winter say the threat of space rocks smashing into Earth is bigger than they thought.
Meteors about the size of the one that streaked through the sky at 42,000 mph and burst over Chelyabinsk in February — and ones even larger and more dangerous — are probably four to five times more likely to hit the planet than scientists believed before the fireball, according to three studies published Wednesday in the journals Nature and Science.
Until Chelyabinsk, NASA had looked only for space rocks about 100 feet wide and bigger, figuring there was little danger below that.
This meteor was only 62 feet across but burst with the force of about 40 Hiroshima-type atom bombs, scientists say. It released a shock wave that shattered thousands of windows and injured more than 1,600 people, and its flash was bright enough to temporarily blind 70 people and cause dozens of skin-peeling sunburns just after dawn in icy Russia.
Up until then, scientists had figured a meteor causing an airburst like the one in Russia was a once-in-150-years event, based on how many space rocks have been identified in orbit. But one of the studies now says it is likely to happen once every 30 years or so, based on how often these things are actually hitting.
Scientists said a 1908 giant blast over Siberia, a 1963 airborne explosion off the coast of South Africa, and others were of the type that is supposed to happen less than once a century, or in the case of Siberia, once every 8,000 years, yet they all occurred in a 105-year timespan.
Because more than two-thirds of Earth is covered with water and other vast expanses are uninhabited deserts and ice, other past fireballs could have gone unnoticed.