Cloudy with a chance of meteorites? Scientists studying the Chelyabinsk meteor that hurtled through the atmosphere over Russia in February have managed to track its trajectory using weather satellites, according to a study in Proceedings of the National Academy of Sciences.
Around 9:20 a.m. local time on Feb. 15 , the approximately 56-foot-wide Chelyabinsk fireball, carrying a mass of 7,000 to 10,000 tons and traveling at about 40,000 mph, exploded in the stratosphere with an estimated energy of 100 to 500 kilotons of TNT, roughly on par with a modern nuclear bomb.
That's because, even though we think of the Earth's atmosphere as being thin and tenuous, "an object entering it at speeds ranging from 12 to 20 kilometers per second (or 50-60 times that of a typical bullet) experiences a strong mechanical shock," the authors wrote.
The blast blew out windows throughout the city of Chelyabinsk, damaging buildings and injuring hundreds. Fragments of the object also fell from the sky as meteorites. The largest thus far, a approximately 1,257-pound behemoth pulled out of Lake Chebarkul last week, made a nearly 20-foot-wide hole in the ice covering the lake (before cracking into pieces).
Numerous dashboard cameras managed to catch at least part of the meteor's path as it blazed through the sky. But in the current study, scientists said they've been able to use Earth-viewing environmental satellites to capture a "distinctive trail of dust, smoke and ice debris" that allowed them to better calculate its trajectory -- and thus, where it may have come from.
"The satellite imagery captures the debris trail left in the wake of the object's traverse, and we can use details of the trail's location to infer trajectory of travel through the atmosphere," they wrote.
The study points to a value of such satellites in tracking these objects -- an important tool as scientists try to predict when a really dangerous asteroid might hit the Earth.
As the authors point out, there's about a 1% chance that an object with a diameter wider than 1 kilometer (about 0.6 miles) will hit Earth in the next millennium. In fact, just hours after the Chelyabinsk incident, a much larger 28-mile-wide asteroid called 2012 DA14 passed below satellites' geostationary orbits, within about 16,800 miles of Earth -- "a very close call by astronomical standards," the authors wrote.
"If used in synergy with other warning and decision aid systems, including resources designed for this purpose," the researchers wrote, "those satellites could play a complementary role in more rapidly directing our attention and response with regard to possible follow-up threats."
Whether these space missiles are expected or not, the satellites can help track the ones that fly by more remote areas and may not leave an impact crater -- as was the case with the 1908 Tunguska impact, whose shock wave wrecked about 850 square miles of Siberian forest.
"In the event of a remote (i.e., far removed from a gallery of Russian dash cams) event," the authors wrote, "the global constellation of Earth-viewing satellites is far more likely to be in a position to assess trajectory and infer the source."