Video courtesy of Sky News
The universe fired two warning shots across the Earth’s bow within the same 24-hour period this past week. The first was a large meteor that exploded over central Russia, which was followed by the closest predicted pass of an asteroid. These two events took place only half a day apart. Remarkably, (scarily so) these major events were not even related.
At about 9:20 a.m. local time (03:20 GMT), Feb. 15, an object streaked across the daytime sky south of the Ural Mountains in Russia, leaving behind a thick, billowing contrail of vapor and smoke. Some 18 miles (30 kilometers) above the ground it suddenly brightened, outshining the Sun, and exploded with an ear-splitting boom. The shock wave from the blast shook buildings, caused a factory roof to collapse, and blew in thousands of windows in the city of Chelyabinsk and the surrounding region. About 1,000 people are reported to have sought treatment after the event—at least 34 were hospitalized, with two being placed in intensive care.
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Video courtesy of First Leaks
The first recording of the cosmic intruder came from an infrared station in Alaska, 6,500 miles from Chelyabinsk (ground zero for the meteor strike). From other recordings along the path of the object it was possible to reconstruct its trajectory and get estimates of its size and mass. The space rock measured about 55 feet (17 meters) across and weighed roughly 10,000 tons, placing it in the small asteroid class. When it entered the atmosphere it was travelling at about 33,000 miles per hour (54,000 kilometers), and it took 33 seconds to descend along a shallow trajectory to a height of between 30 and 45 kilometers, at which point it blew apart, releasing nearly 500 kilotons of energy.
An encounter of this size is expected to happen about once a century. In fact, the last comparable one occurred 105 years ago when an asteroid, or piece of a comet nucleus, about 160 feet (50 meters) across exploded above the Tunguska region of Siberia, laying waste to hundreds of square kilometers of trees.
Amazingly, the latest Russian fireball appears to have been completely unconnected with the asteroid 2012 DA14, which, as predicted, flew harmlessly past the Earth just hours later, at the very close range of 17,100 miles (27,500 kilometers).
Video courtesy of Russia Today
Mercifully, there were no fatalities this time around. But it could easily have been a different story, especially if the meteor/asteroid had reached the ground in one piece. Friday’s strike was a wake-up call that, despite our improved knowledge of near-Earth asteroids, we can still be caught unaware.
Astronomers are pretty sure they know the whereabouts and trajectories of every asteroid larger than 18 miles (30 kilometers). But at the other end of the scale, we’re still pretty much in the dark. Estimates suggest that 98 percent of asteroids that are 50 meters or so across have yet to be detected. There could be hundreds of thousands of these smaller asteroids in the solar system, each capable of devastating a city.
Last week’s unexpected arrival underscores just how vulnerable we are and why NASA should be funded to develop systems capable of mitigating the asteroid threat. These must range from long-term strategies to deflect large objects that pose a threat decades in the future, to fast-response intercept missions that can take out city-buster type asteroids with nuclear explosions possibly just hours or days ahead of impact.