Fighter pilots have a saying — it’s the bogey you don’t see that will generally get you. With International Asteroid Day 2018 fast approaching, that's a maxim we should pay close attention to.
It was on full display on February 15, 2013. That day, the astronomical world had its gaze fixed over the eastern Indian Ocean, off Sumatra, where Asteroid 2012 DA14 was due to give the Earth a relatively close shave, missing terra firma by just 17,200 miles, well inside the orbit of the moon (an altitude of 240,000 miles), and even those of geostationary satellites (22,000 miles). The asteroid measured 150 feet across and its approach was well understood, as astronomers had been tracking it for some time. It arrived right on schedule and buzzed the planet just as predicted. The event would likely have made a good story on the local evening news, sandwiched between the weather report and sports scores. But just hours before 2012 DA14 flashed past the Indian Ocean, it was upstaged by a another rock — one with no name. An asteroid about 55 feet across cut a gash in the sky over the Siberian city of Chelyabinsk, Russia. It entered the Earth’s atmosphere at some 40,000 mph and the intense atmospheric pressures tore it apart less than fifteen miles above the surface. The resulting airburst was thirty to forty times the force of the atomic bomb exploded over Hiroshima. More than 1,000 people were injured. But the size of the Chelyabinsk airburst is not its most worrisome characteristic. It’s the fact that no one saw it coming. The lessons of 2012 DA14 and Chelyabinsk stand in stark relief. The former demonstrates how well we can predict the movement of detected objects in our immediate celestial neighborhood; the latter shows how far we have to go in finding them.
It’s worth noting that if the United States understood a potentially lethal Earthly foe as little as we understand the asteroid threat, it would be considered a national emergency. Impact events are unique among natural disasters in two important respects. First, we have strong evidence that in addition to local devastation, they can create planetary-level catastrophe; second, and more significant, we can do something to prevent them provided we can understand the threat and then outperform the dinosaurs at three key competencies: detection, deflection and decision-making.
Understanding the threat
The analysis of the Chelyabinsk event is possible thanks to the Comprehensive Test Ban Treaty Organization (CTBTO) which operates a network of infrasound sensors around the world that detect low-frequency sound waves, looking for nuclear explosions. The Chelyabinsk meteor was in fact the largest infrasound event the CTBTO has ever recorded and also the largest recorded meteor strike since 1908 when an even larger object exploded over a different part of Siberia, smashing 825 square miles of forest near the Tunguska River. Subsequent investigation by NASA’s Meteoroid Environment Office at the Marshall Space Flight Center revealed the likely origin of the space rock, and the conclusions are not reassuring: “[it’s] a typical asteroid from beyond the orbit of Mars,” said NASA’s Bill Cooke. “There are millions more just like it.” So while all this analyis is useful, it serves to highlight the fact that this particular rock escaped our notice until it exploded over a city.
Beyond the obvious immediate threat posed by an asteroid strike, an unexpected, nuclear-sized airburst over any country, but especially one armed with nuclear weapons, creates broader security concerns. Had such an unexpected event suddenly lit the skies above, say, Tel Aviv, or Pyongyang, the potential implications for global security are disquieting to say the least. Dr. Joan Johnson-Freese, Professor of National Security Affairs at the Naval War College, addressed this issue before Congress. “Given the complex political state of the world, it is clearly imperative that government officials have accurate scientific data to distinguish between meteorites and missile attacks,” she said.
Most primary school students are familiar with the well-supported theory that a meteor barreled into the Earth near Mexico’s Yucatan Peninsula 65 million years ago, playing a key role in triggering the demise of the dinosaurs. Less well known is a theory now gaining currency that an earlier, similar event may have created the conditions which allowed the dinosaurs to rise in the first place, the result of another mass extinction at the end of the Permian period. While the mass extinction that wiped out T-Rex and his kin also took out an estimated 70 percent of all species on the planet, the Permian extinction was even more thorough. It killed off 80 percent of Earth’s species and evidence now suggests that this event may also have been sparked by a major impact. Both are relevant since they speak to the ability of an asteroid impact to trigger global cataclysm.
Meteor Crater in Arizona is an example of an impact event with local consequences. Estimates are that 50,000 years ago an object 160 feet across struck the Colorado Plateau at this point with the force of a ten megaton nuclear warhead. The crater it created is today nearly a mile across and 550 feet deep. If the Meteor Crater asteroid were to strike today, it would be a city-killer.
Dr. Ed Lu, CEO of the asteroid-hunting B612 Foundation said in testimony to Congress: “We citizens of Earth are essentially flying around the Solar System with our eyes closed. Asteroids have struck Earth before, and they will again — unless we do something about it. The probability of a 100 Megaton asteroid impact somewhere on Earth this century is about 1%. The odds of another Tunguska five Megaton event this century are much higher, about 30%. What if I told you there is a 30 percent chance of a random 5 megaton nuclear explosion somewhere on Earth this century? What would we do to prevent it?”
In February 2013, NASA catalogued the 10,000th Near-Earth Object (NEO). Many more await discovery — obviously, the Chelyabinsk meteor was on the latter list. Recognizing both the threat and the need to understand it far better, in 1998, Congress charged NASA with cataloguing around 90 percent of the asteroids of 500 feet or more in diameter within ten years. That goal was not achieved, at least partly because, not for the first time, Congress sought to achieve its ambitions without concomitant budget appropriations. Still, real progress is being made.
Currently, the Space Guard Survey has identified what we believe are all of the 1,000 large asteroids, 3,200 feet and larger in diameter. Some 30,000 asteroids from 500 to 3,200 feet across may lurk in our neighborhood, and with current tools we hope to be able to spot and track them all by 2030. The smallest rocks, up to 500 feet across, remain largely beyond our ability to detect. There may be millions of those.
The efforts to find out more about our celestial neighborhood and the threats within it are gathering steam. The Near Earth Object Observation (NEOO) Program detects, tracks and assesses Earth-approaching asteroids using assets based on the ground and in space. NASA is also funding a project at the University of Hawaii called Asteroid Terrestrial-Impact Alert System (ATLAS). In California, NASA’s 70-meter Goldstone antenna is part of the Deep Space Network, and one of two dishes that can image asteroids using solar system radar. Any NEO findings are sent to the Minor Planet Center, paid for by NASA and operated by the Smithsonian Astrophysical Observatory for the Paris-based International Astronomical Union. In addition, the Large Synoptic Survey Telescope (LSST) has been fully funded and will be online by 2022. LSST is designed to find millions of NEOs that are either too small or too distant to be detected via existing telescopes. In early 2017, however, NASA chose not to fund the Near Earth Object Camera (NEOCam) mission, which was also designed to look for NEOs.
Asteroid-hunting is an increasingly international affair. One such effort is called NEOShield, a research program funded by Europe, Russia and the US. The European Space Agency has also launched the NEO Coordination Centre to better organize scientific work on the issue. But like the response to government plans for human exploration, the private sector sees that there’s more to do in the face of such a potentially disastrous threat.
The B612 Foundation, for example, is developing a technology called synthetic tracking, which allows current telescopes to more reliably identify NEOs that are too small, too close and too fast to be otherwise seen. The high-speed data processing necessary for synthetic tracking has already passed initial testing with existing ground-based telescopes.
First things first. Forget you ever saw the movie Armageddon. Various options exist for addressing an asteroid threat. All deal in one way or another with our ability to apply significant force to the incoming object, which does not mean simply blowing it up, as Armageddeon’s producers would have us think.
“The key is not to try to destroy the thing, but to make sure it misses,” says Gen. Kevin P. Chilton, NASA astronaut and former commander of US Strategic Command and Air Force Space Command. “And that does necessarily, depending on how soon you address the problem, require tremendous amounts of force… The biggest problem is early enough detection of the threat and being able to then have the appropriate equipment at hand to be able to address it before it becomes inevitable.”
The kind of solutions needed relate to how much time we have to work with. In a situation with a small amount of time and a large amount of rock, applying force with a nuclear warhead may be the only way to deflect its flightpath. More time and less rock means that a “kinetic impactor” might work, essentially slamming a heavy, fast moving spacecraft into the offending boulder, nudging it in a different direction. Another compelling technology is called a Gravity Tractor. The concept uses forces of nature to our advantage. A small spacecraft, the Gravity Tractor, would intercept a troublesome object and fly in close formation with it. Since all objects have mass, which creates a gravitational field, the gravity created by the spacecraft itself would, over time, gently tug the object toward it, altering its flightpath. The course correction would be slight, but if caught early enough even a small trajectory change would do the trick. Armageddon cancelled.
More fanciful ideas include flying a swarm of “mirror bees” to an asteroid, which would focus sunlight on part of the rock, vaporizing it and creating a jet of materials that would alter its trajectory, or wrapping the rock in a kind of foil that would act as a solar sail, allowing the solar wind to push it off course. Operationalizing any of these will require a lot more work, but as B612 notes, we have an advantage our predecessors lacked. “The dinosaurs didn’t have a space program.”
Planetary defense is about more than sound science and effective technology. The good news is that our ability to detect NEOs is rising, but this advance creates some new problems. B612 estimates that our rate of asteroid detection will rise from about 30 per week now to thousands per week within a few years. That tsunami of data will make analysis and action harder. It will put significant pressure on the ability of our politics, both domestic and international, to make timely, informed decisions. In America, the inability of our politics to make effective decisions about issues large and small is not comforting. The international environment is now more complex than at any time in a generation. But any effort to deflect an incoming NEO will be international in character. We must learn to work together better — as many nations have in the International Space Station (ISS) project.
B612 is developing the Asteroid Decision Analysis Machine (ADAM), in order to better understand, analyze, and assess impact and deflection scenarios. This tool involves creating a standard threat analysis formula that all nations and others in the planetary defense community will use. Without a common assessment of both incoming threats and deflection options, international action is all but impossible. Regardless of the exact approach to achieving this, it seems clear that the public needs a better understanding of the threats we face and how we can effectively manage them. Failing to do so endangers the entire enterprise of asteroid detection and deflection.
Building an effective international detection and deflection apparatus requires credible, effective and transparent leadership. That leadership must result in a realistic and effective structure, one able to act quickly and transparently, supported by the political, technical and monetary resources necessary to sustain it over time. Canada, Europe, Japan, Russia and the United States have all done this with the International Space Station. To stare down the NEO threat, they should grow the ISS family to include more large partners such as China and India, and small ones such as the United Arab Emerates. The international community of nations and the private sector will have to work closely to build the technical and political tools necessary to defend the planet.