Skyfall: will a Russian meteor and an asteroid flyby change our minds about the NEO threat?
by Jeff Foust
|“The reason why it wasn’t detected by telescopes on Earth is because it literally came out of the day side of our planet. It was in the daylight sky” and thus couldn’t be seen, Cooke explained.|
The events of February 15th may have changed that risk calculus, though. In the weeks leading up to Friday, astronomers were hoping to raise awareness of the NEO population with the close flyby that day of asteroid 2012 DA14. That object, about 45 meters in diameter, passed 27,700 kilometers from the Earth’s surface: closer than satellites in geosynchronous orbit, although on a trajectory that did not intersect the orbit itself. The flyby offered an opportunity to remind people that, while 2012 DA14 itself posed no impact risk to the Earth or its satellites, it was a reason to keep scanning the skies looking for objects that might be more dangerous.
That flyby, though, was overshadowed by the unexpected. At about 9:20 am local time Friday morning (10:20 pm EST Thursday night), a meteor streaked across the skies of southern Russia, disintegrating at an altitude of about 20 to 25 kilometers over Chelyabinsk Oblast, a region in the southern Ural Mountains on the border of Kazakhstan. A few minutes later, the blast wave from that disintegration hit the oblast’s capital, Chelyabinsk, a city of 1.1 million people. The blast shattered thousands of windows and damaged buildings, including a zinc factory and the arena used by the city’s hockey team. Russian media reported that 1,200 people were injured, primarily by glass from broken windows; few of those injuries were serious, though, and no one was killed.
One immediate question was whether the Chelyabinsk meteor was related somehow to 2012 DA14. By Friday afternoon, NASA scientists had ruled out any connection between the two. In a teleconference with reporters, Paul Chodas, a research scientist in NASA’s Near Earth Object Program Office at JPL, said the direction of the meteor’s approach—approximately north to south, compared to 2012 DA14’s south-to-north trajectory—and a much higher velocity led them to conclude that the timing of the two events was “an incredible coincidence,” he said.
Based on observations, including data from a network of infrasound stations used to monitor for nuclear tests, scientists estimate the object that struck Chelyabinsk was 17 meters in diameter and weighed about 10,000 tons, releasing the energy equivalent of approximately 500 kilotons of TNT. “My guess is that this would be a stony meteorite, maybe a chondrite,” said Bill Cooke of the Meteoroid Environments Office at NASA Marshall on Friday’s call with reporters, because it disintegrated at a higher altitude. Discoveries of meteorite fragments on Sunday, as reported in the Russia media, appear to confirm this assessment of its composition.
But how did the object escape detection by the various surveys for NEOs? Part of the reason is its small size, but its orbit played a key factor as well. “The reason why it wasn’t detected by telescopes on Earth is because it literally came out of the day side of our planet. It was in the daylight sky” and thus couldn’t be seen, Cooke explained. The object was in an elliptical orbit that carried it from the asteroid belt in to nearly the orbit of Venus; it was heading away from the Sun when it hit the Earth.
Such orbits have long been recognized as a blind spot in current asteroid search efforts. There have been proposals to place space telescopes in orbits closer to the Sun, such as the vicinity of Venus, which could look out and detect such objects without interference from the Sun. The B612 Foundation’s Sentinel spacecraft, for example, would operate in such an orbit (see “A private effort to watch the skies”, The Space Review, July 2, 2012).
A call to action? Will this event make any difference in raising public—and political—awareness of the NEO impact threat, and thus spur action to fund enhanced searches or even technologies that could be user to divert a threatening object? Immediately after the meteor, a few members of Congress suggested a need to redouble efforts in this area.
|“This should serve as a wake-up call,” Rohrabacher said.|
“Today’s events are a stark reminder of the need to invest in space science,” said Rep. Lamar Smith (R-TX), chairman of the House Science Committee, in a statement Friday. “We should continue to invest in systems that identify threatening asteroids and develop contingencies, if needed, to change the course of an asteroid headed toward Earth.” He added this his committee would hold a hearing “in the coming weeks” on the subject.
The committee’s vice chairman, Rep. Dana Rohrabacher (R-CA), has long been an advocate of enhanced NEO search efforts and impact mitigation studies, and needed little convincing by Friday’s events.
“This should serve as a wake-up call,” he said in a separate statement. “We have been spending millions to find and track asteroids and comets, but the indications are that this one was so small that we aren't even looking for objects of this size. What concerns me even more, however, is the fact that we have no plan that can protect the Earth from any comet or asteroid. So, even if we find one that will hit us, we might not be able to deflect it.”
Planetary defense is a bipartisan issue. In an op-ed in the Washington Post Saturday, Reps. Rush Holt (D-NJ) and Donna Edwards (D-MD), the ranking member of the House Science Committee’s space subcommittee, said that a mandate in NASA’s 2005 authorization act calling on the agency to find 90 percent of NEOs at least 140 meters across by 2020 has been “chronically underfunded.” “Last year the project received about $20 million, far less than the $50 million that the National Research Council estimated in 2010 was needed to reach the congressional goal by 2030, a decade late,” they wrote.
NASA, though, isn’t the only organization in the asteroid search game. There are various, although smaller, efforts in other nations. There is also now interest in the private sector, most notably the B612 Foundation, which is seeking to raise several hundred million dollars for its Sentinel space telescope. “The undetected meteor explosion over Chelyabinsk on February 15 is our wake-up call that the Earth orbits the Sun in a shooting gallery of asteroids, and that these asteroids sometimes hit the Earth,” former astronaut Ed Lu, CEO of B612, said in a statement.
Lu said that Sentinel would be able to discover 90 percent of the large asteroids (140 meters in diameter and larger) over the course of its mission and about half of the asteroids in the size range of 2012 DA14. He didn’t say how well it could detect smaller objects, like the one that struck Russia; while Sentinel would be in an orbit that could detect objects in orbits like it better than groundbased telescopes, its small size could still hinder detection.
Even the companies that have emerged in the last year to pursue asteroid mining have shown an interest in NEO detection efforts as well (see “Asteroid mining boom or bubble?”, The Space Review, January 28, 2013). Planetary Resources co-founders Peter Diamandis and Eric Anderson said the company’s Arkyd-100 series of asteroid prospecting spacecraft can also help in cataloging NEOs. Later, as the company plans to extract ices and other resources from asteroids, it “expects to be able to help in the (slight) re-direction of these rocks to keep the Earth safe.”
|Sometimes we need to be hit over the head by a tragedy in order to take action to prevent it from happening again. The Chelyabinsk meteor was, perhaps, more of a tap on the shoulder.|
Deep Space Industries, the new entrant into the asteroid mining business, proposed in a statement deploying “sentry lines” of its Firefly small satellites in Earth orbit that could collect data on NEOs as that make close flybys like 2012 DA14. The company claimed it could put ten such spacecraft in Earth orbit within four years and for less than $100 million. “While our primary mission is the harvesting of asteroid resources,” said company chairman Rick Tumlinson, “we believe that virtually the same effort and technology can be applied to removing this threat to our precious planet.”
The common theme of these statements is that the Russian meteor and, to a lesser extent, 2012 DA14, serve as warnings that we live in a cosmic shooting gallery and should invest more in systems to discover and, potentially, deflect such objects before they do more harm. That’s an understandable sentiment, and plays into the fact that, as a society, we tend to be reactive more that proactive, responding to a calamity—natural or human-made—after one happens to either prevent it from happening again or being more prepared the next time around. As both Rohrabacher and Lu said, these events served as a “wake-up call.”
But is the ringing of that wake-up call loud enough? Perhaps not. The Russian meteor did only relatively modest damage to the city of Chelyabinsk, and fortunately no one was killed. Russian officials estimated the damage to buildings in the city at one billion rubles (US$33 million), and that many of the broken windows had already been fixed as of Sunday. By comparison, Congress passed last month a $51-billion supplemental spending bill to pay for damages and other relief from Hurricane Sandy last fall.
The event will likely fade from the news, at least outside of Russia, as other events vie for the media’s attention. Most Americans probably didn’t even know of the existence of Chelyabinsk before Friday’s meteor, unless they know their Cold War history or follow Russian professional hockey; they’re unlikely to keep it in the forefront of their thoughts in the weeks and months to come.
The topic will get some attention in Congress, particularly by the House Science Committee, and language of some kind about NEO searches may make it into a NASA authorization bill Congress is expected to take up later this year. But there’s no guarantee that appropriators will follow up with any additional funding for NEO searches. With so many other issues competing for attention, particularly the automatic across-the-board budget cuts known as sequestration slated to go into effect on March 1 unless Congress and the White House make a deal to avert them, trying to win support for any kind of spending increase will be difficult, even a modest one for NEO searches.
The B612 Foundation may actually be a little better positioned, as it’s not beholden to a government agency for funding, and thus not subject to the parochial politics of Capitol Hill. The organization can seek out a wide range of donors from around the world to support their efforts. However, they still face the challenge of raising several hundred million dollars, something the organization notes is routinely done for non-profit terrestrial projects, like museums and hospitals, but has yet to be done in space.
And the role commercial entities can play is unclear as well. While they can play a role in studying and, perhaps one day, helping divert threatening objects, their near-term role is limited, and they run the risk of appearing too opportunistic. In his organization’s statement, Lu felt the need to make it clear that the B612 Foundation wasn’t in it for profit. “The foundation is not undertaking this project for profit; we are a non-profit corporation. Our motivation is strictly to ensure the survival of life on Earth—all of it.”
Again, as a society we tend to be reactive, and sometimes we need to be hit over the head by a tragedy in order to take action to prevent it from happening again. The Chelyabinsk meteor was, perhaps, more of a tap on the shoulder, a relatively gentle reminder that the inner solar system can be a hazardous place. Will it be enough to convince politicians and the public that we should be doing more to catalog NEOs and plan how to deal with a threatening object in the future?