One of the most damaging meteor strikes in recorded history occurred earlier this year over the frigid Russian town of Chelyabinsk. The meteor injured as many as 1000 people when it entered the Earth's atmosphere over the Russian city creating shockwaves that shattered windows and rained shards of debris on people in the city. Scientists were later able to determine the meteor weighed in the area of 10,000 tons and is a chrondite.
Chrondite is one of the most common kinds of asteroids in the Earth's orbit. NASA scientists have been reworking their astronomic models having to do with asteroids and meteors of this type and have found their mathematical models were incorrect. NASA now says that the number of similar sized objects that could hit the Earth is higher than previously believed and the damage these objects can do is much greater than expected.
NASA's Bill Cooke said:
If you look at the number of impacts detected by US government sensors over the past few decades you find the impact rate of kiloton-class objects is greater than would be indicated by the telescopic surveys.
Over the past few decades we've seen an impact rate about seven times greater than the current state of the telescopic surveys would indicate.
Cook also notes that the nuclear model used to estimate the amount of explosive force asteroids could cause had been overestimating the blast impact of this type of air-bursting meteor. However, the model had been significantly underestimating the heat meteors of this type generate and the damage that can be caused by the shock wave of air they create as they plummet through the atmosphere.
NASA scientists also offered some more information on the Chelyabinsk meteor, which is the largest to hit the Earth since the Tuguska event 1908. That meteor destroyed 2150 square kilometers of Siberia with a single airburst. NASA says that the Chelyabinsk meteor arrived unexpectedly in part because it was coming at the Earth with the sun behind it.
The meteor entered the atmosphere at 42,500 mph with the majority of its mass being destroyed in a detonation 23 km above Russia. Scientists estimate as much as 13,000 pounds of the meteor survived the blast above the Earth. The meteor also had fractures formed by an impact with another space rock that left veins of silicates throughout the asteroid. Those veins of silicates made the meteor much more likely to break up during atmospheric entry.
SOURCE: The Register