Nobody saw the object coming.
It's enough to make some lawmakers wince. On Friday, Lamar Alexander (R) of Tennessee and chairman of the House Science, Space, and Technology Committee, issued a statement regarding the two events that noted that the committee will hold hearings in the near future to explore ways to improve efforts to detect asteroids as well as to deal with any deemed a potential threat to the planet.
Given the size of the Chelyabinsk asteroid, astronomers estimate that an event like this occurs on average every 100 years. Yet smaller objects also can arrive with little or no warning, and explode in a loud, spectacular fashion, even with no damage on the ground. And they hit more frequently.
These surprise visitors are among the near-Earth objects that keep Kalait Ramesh awake at night.
"Historically, we've had relatively low population density. These things tended to happen in areas where nobody sees them or nobody remembers them," says Dr. Ramesh, a professor of mechanical engineering at the Johns Hopkins University whose studies of stress on various materials has led him to include asteroids in the mix of materials.
"But as our population's gone up, it's gotten to the point where these things can have a big impact. My biggest worry is that this will happen in a place where there is significant political instability or two countries on the verge of a war," he says.
An event like Friday's Chelyabinsk asteroid explosion could be mistaken for an attack, he says.