Don Davis
Artwork by Don Davis shows a meteor streaking over Chelyabinsk. More of Davis' art is on his website.
By Alan Boyle, Science Editor, NBC News
Now that they've worked out the orbital path of the meteor that blew up over Russia last month, scientists are saying that the asteroid behind the blast crossed Earth's orbit regularly for thousands of years. Two weeks ago, it looked as if the 1.1 million residents of the city of Chelyabinsk had been hit by a cosmic stroke of bad luck?? but now they're talking about turning the most powerful asteroid impact in more than a century into a tourist attraction.
The Feb. 15 aerial explosion and the shock wave it set off caused an estimated $33 million in property damage, much of it in the form of shattered windows and weakened walls. It also injured about 1,200 people, with most of them hurt by the flying glass from those windows. Authorities started the cleanup work almost immediately, while researchers rushed to figure out the scale of the explosion.
Based on the readings from infrasound sensors stationed all over the world to monitor nuclear-weapons tests, NASA said the energy release was equivalent to 500 kilotons of TNT, or roughly 30 times the energy released by the atomic bomb dropped on Hiroshima at the end of World War II. That translated into an object about 17 meters (55 feet wide), weighing 10,000 tons. The space agency said it was the biggest cosmic impact recognized since the 1908 Tunguska asteroid blast that leveled millions of trees in Siberia.
Less than a week after the blast, Colombian astronomers worked out a rough orbital path for the Chelyabinsk asteroid, based on an analysis of the videos captured by dashboard cameras and traffic cams in the area. On Friday, NASA produced a more definitive orbital track, based not only on the videos but also on the readings from the federal government's space sensors. The report took advantage of a recently signed agreement with the Air Force Space Command for the public release of previously hush-hush data.
Sizing up a superbolide
Friday's assessment is the first entry in a new NASA database for fireballs and bolide reports, which classifies the Chelyabinsk meteor as a "superbolide."
The latest readings confirm the conclusion that the object's orbit ranged from the main asteroid belt, beyond the orbit of Mars, to well within Earth's orbit. They also show that the Chelyabinsk asteroid's approach couldn't have been detected by ground-based optical telescopes because the space rock was hidden in the sun's glare.
P. Chodas et al. / NASA / JPL-Caltech
An orbital diagram shows the pre-impact orbit of the asteroid that blew up over Russia on Feb. 15, based on the track of its atmospheric entry. The asteroid came at Earth from the sunward side.
"The impactor had likely been following this orbit for many thousands of years, crossing the Earth's orbit every time on its outbound leg," NASA's Near-Earth Object Program Office said in Friday's assessment.
The fresh readings tweaked previous estimates of the object's size and brightness as well: NASA said the meteor was 17 to 20 meters wide (55 to 65 feet wide), and reached peak brightness at an altitude of 14.5 miles (23.3 kilometers), when it was traveling at a speed of 41,760 mph (18.6 kilometers per second). There's also quite a bit of discussion about the energy release ? and why the new estimate for impact energy (440 kilotons, which includes energy lost during atmospheric entry) is so much bigger than the fireball's radiated energy (90 kilotons, which applies only to the blast).
From the get-go, astronomers have said that the Russian meteor was not connected with the close flyby of a much bigger asteroid, known as 2012 DA14, which took place later on the same day. Friday's assessment confirms that lack of a connection ? not only because the two orbital paths were markedly different, but also because the two asteroids had different compositions.
NASA said a spectral analysis of 2012 DA14, conducted by researchers at the Massachusetts Institute of Technology, suggests that the asteroid is a relatively rare carbonaceous chondrite "with abundant calcium- and aluminum-rich inclusions."
"On the other hand, meteorite fragments being recovered from the fireball event are reported as silicate-rich ordinary chondrites, a completely different and unrelated class of meteorites," NASA said. "About 80 percent of all meteorite falls are in the ordinary chondrite category."?
Andrei Romanov / Reuters
A local resident shows a fragment thought to be part of a meteorite collected in a snow-covered field in the Yetkulski region, outside the city of Chelyabinsk.
Taking pride in a superbolide
Scientists may classify the Russian meteorites as an unremarkable kind of space rock, but they're extra-special to the folks in Chelyabinsk. For one thing, such meteorites could be worth more than their weight in gold on the collectors' market. Some have estimated their value at $2,200 per gram. For another thing, the region's residents are now talking about capitalizing on the international interest generated by the impact.
"Space sent us a gift, and we need to make use of it,"?Natalia Gritsay, head of the region?s tourism department, told Bloomberg News this week. "We need our own Eiffel Tower or Statue of Liberty."
Among the ideas being debated: building a "Meteor Disneyland" theme park that re-creates the glass-shattering event, or organizing a cosmic music and fireworks festival, or erecting a beacon-tipped pyramid at nearby Chebarkul Lake, where meteorite fragments have been found. Tourist companies are already starting to sell group tours to Chelyabinsk at $800 a person, Bloomberg News reported.
When the meteor exploded, many of the region's residents feared that it was a plane crash, or a missile strike, or even the end of the world. Now it's starting to look as if the superbolide is the best thing to hit Chelyabinsk in years.
?Nobody had heard about us, and now all the world knows,? the region's governor, Mikhail Yurevich, told Bloomberg News. ?We can earn some dividends on that."
Yekaterina Pustynnikova / Chelyabinsk.ru via AP
Click through scenes from Russia's Chelyabinsk region, where a huge meteor fireball set off alarms, injured hundreds of people and caused a factory roof to collapse.
More about the meteor:
Tip o' the Log to space illustrator Don Davis and Spike MacPhee.
Alan Boyle is NBCNews.com's science editor. Connect with the Cosmic Log community by "liking" the log's?Facebook page, following?@b0yle on Twitter?and adding the?Cosmic Log page?to your Google+ presence. To keep up with Cosmic Log as well as NBCNews.com's other stories about science and space, sign up for the Tech & Science newsletter, delivered to your email in-box every weekday. You can also check out?"The Case for Pluto,"?my book about the controversial dwarf planet and the search for new worlds.
Source: http://cosmiclog.nbcnews.com/_news/2013/03/02/17160360-meteor-lurked-for-thousands-of-years-before-blasting-russia-experts-say?lite
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