Don Davis

Artwork by Don Davis shows a meteor streaking over Chelyabinsk. More of Davis' art is on his website.

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."

Slideshow: Meteor streaks over Siberia

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.

Launch slideshow

More about the meteor:

• Experts get set for the next asteroid
• How to 'hear' the Russian meteor
• NBCNews.com archive on asteroids

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.

As of now, there's no comet or asteroid that's definitely due to smash into our planet, but experts say it's high time to figure out how to deal with the uncertainties, misunderstandings and political wrangling that will inevitably arise during the asteroid alerts to come.

Last week's hubbub over the asteroid 2005 YU55, which passed within 200,000 miles of Earth, set the scene for a seminar on near-Earth objects sponsored in Boulder, Colo., by the Secure World Foundation. The public's interest in the harmless flyby was just a foretaste of what could happen when astronomers spot a rock that has a significant chance of hitting Earth.

And it is a question of "when," rather than "if."

Several potential impacts have been flagged over the past decade. In most of those cases, further observations — including observations gained from "pre-discovery" images of the objects in question — have ruled out a collision. But some of the cases are still on NASA's list — including 1999 RQ36, the 560-meter-wide (600-yard-wide) asteroid that's judged to have a 1-in-1,750 chance of hitting Earth sometime in the next 200 years. That rock will be targeted by NASA's Osiris-Rex probe, due for launch in 2016.

Then there's Apophis, the asteroid that sparked a scare in 2004 when its chances of impact were briefly set as high as 1-in-37. Since then, further analysis has reduced the odds to 1-in-250,000 for 2036. A new round of radar observations in 2013 could reduce the chances even further, to essentially zero, or conceivably raise them again.

That's one of the problems for asteroid-trackers: The stated odds of impact are calculated on the basis of how much or how little is known about a near-Earth object's orbit. If the possible track at a particular given time stretches for hundreds of thousands of miles, and Earth happens to lie anywhere on that track, astronomers have to acknowledge there's a chance that Earth will end up getting hit. As the orbital predictions are refined, the stated odds may go up or down. In almost all of the cases to date, an Earth impact is eventually excluded, and the odds go down to zero.

More alerts ahead
As more powerful telescopes come online, there'll be more asteroids that may be added to NASA's impact risk list — and potentially more up-and-down asteroid alerts.

"Those are going to happen every year, or at least every decade," David Morrison, director of the SETI Institute's Carl Sagan Center for the Study of Life in the Universe, said at this week's seminar.

And sometimes the asteroid actually hits: That was the case in 2008, when a boulder-sized asteroid known as 2008 TC3 slammed into Sudan just hours after its discovery. Astronomers knew almost immediately that there'd be an impact, and that there'd be no significant damage in the desert. However, the event demonstrated that near-Earth objects could come at us from right out of the blue.

Astronomers are getting a good handle on tracking the asteroids that are big enough to spark mass extinctions. But they also say thousands of bad-news asteroids that are wider than 100 meters (330 feet) are yet to be detected. Roughly a million yet-to-be-detected asteroids are smaller than that, but still capable of causing damage. 

The bottom line is that the most immediate threats from the sky are not likely to be the huge objects portrayed in movies like "Deep Impact" or "Armageddon," but the smaller ones that are nevertheless capable of destroying a city or sparking a tsunami.

"Chances are we wouldn't see it," said Mark Boslough, a researcher at Sandia National Laboratories who recently drew up a computer simulation of the 1908 Tunguska blast. Boslough said the object that caused the Tunguska explosion might have been just 40 meters (130 feet) in diameter, but still flattened 500,000 acres of Siberian forest.

Emergency preparedness
So how can you prepare for something like that? That's what the experts have been trying to figure out: This week's seminar focused on a U.N.-sponsored process to draw up an international emergency preparedness plan for asteroid and comet impacts.

As it stands now, the plan calls for formalizing a network of sky-watchers, most likely including folks from NASA's Near Earth Object Program and the groups that will be part of the European Space Agency's SSA-NEO effort. If something needs to be done about studying or diverting a potentially threatening asteroid, a separate team of planners (known as a Mission Planning and Operations Group) would set up the space mission; a diplomatic group would be charged with signing off on that mission; and the U.N. Security Council would give the final go-ahead.

Why such an involved process? In the movies, NASA just goes ahead and blows up the planet-killer. But in real life, trying to move or break up a truly large asteroid could take years of effort, and temporarily raise the risk for one region of the world while lowering it for a different region. For example, if an asteroid's track is projected to end in a Pacific Ocean impact, do you move the asteroid off track to the east, putting the Americas at greater risk for a while ... or to the west, temporarily putting Asia in the crosshairs. And if something goes wrong with the operation, who would be held at fault? The U.N.-backed effort, which is expected to result in concrete recommendations by 2013, is aimed at anticipating these tricky political issues.

For relatively small asteroids, the advance warning might be on the scale of mere hours, days or weeks, and the response might look a lot like a Katrina-level hurricane evacuation. On the other end of the scale, it could take decades to resolve an Apophis-style situation.

Education effort needed
The long-term scenario would require a lot of education about the observational uncertainty, about the campaign to divert the asteroid, and about the potential effects of impact. For example, based on the Tunguska example, a 50-meter-wide (165-foot-wide) object could wipe out an area the size of a major city. (The Earth Impact Effects Program lets you tinker with the parameters of a cosmic impact and find out how far you'd have to run.)

If it takes until the year 2036 to resolve the Apophis situation, the right time for addressing the issue of near-Earth objects is ... right now. In fact, some folks have already organized school projects on the subject.

"Let it grow up with the kids as they grow older," said retired Apollo astronaut Rusty Schweickart, who helped organize efforts by the Association of Space Explorers and the B612 Foundation to address the asteroid issue.

What do you think? Are near-Earth objects on your list of things to worry about? Or are they on your list of things to look forward to, thanks to the Obama administration's plans to send astronauts to an asteroid by the mid-2020s? Feel free to weigh in with your comments below.

Update for 3:25 p.m. ET Nov. 17: Rusty Schweickart added a little perspective about Apophis in a follow-up email:

"I’d like to remind people that Apophis is No. 7 on the list of objects with non-zero impact probability (ranked by Palermo level), and if you include those seen in the last 60 days, it's No. 8.  Some of the others are pretty interesting and, while still having a low probability of impact, are more threatening than Apophis.

"Unfortunately more people have heard of Apophis, given its history, and don't seem to get that its impact probability is now ridiculously low ... and very likely to go to no threat at all when we track it again in 2013.  Not so with some of the others ... but they’re not 'known' by the public.  Yet."

Also, Harvard instructor David Ropeik, an expert on risk communication (and former msnbc.com contributor), has published his own report on the Boulder seminar as a Big Think blog item, titled "The Sky IS Falling. Should We Worry?" 

Update for 8 p.m. ET Nov. 18: Another participant in the Boulder seminar, Carolyn Collins Petersen, explores "The Undiscovered Country of Small Bodies" on her blog, The Spacewriter's Ramblings.

Update for 3 p.m. ET Nov. 19: My colleague from Sky & Telescope, Kelly Beatty, reports on the Boulder seminar in a posting titled "If an Impact Looms, Then What?"

More about asteroids:

• To fight off asteroids, humans must cooperate
• Largest digital camera hunts killer asteroids
• Here's how to counter a killer asteroid
• Mystery returns to the case of the dino-killing rock
• Interactive: Close encounters of the asteroid kind

I attended the Secure World Foundation's seminar as a participant, and the foundation paid some of my expenses for the trip. The seminar sessions were conducted under the Chatham House Rule for information sharing. The direct quotes used here were cleared by individual speakers after the sessions.

Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter or following the Cosmic Log Google+ page. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.