At 9:20 in the morning on Feb. 15, 2013, Sergei Serskov looked out his window in the Russian town of Chelyabinsk and saw a bright light streak across the sky. What he witnessed, according to the BBC, was the disintegration and burn-up of a 20-meter asteroid on its way to Earth.
“I looked out the window and saw a huge line of smoke, like you get from a plane but many times bigger,” he said. “A few minutes later the window suddenly came open and there was a huge explosion, followed by lots of little explosions. It felt like a war zone and it lasted about 20 to 30 minutes.”
The subsequent blast was strong enough to send over a thousand people to the hospital and damage 7,000 buildings.
Long before this, 66 million years ago, it is believed that a 10-kilometer asteroid that hit the Yucatan caused an extinction event wiping out most species including, famously, the ground-based dinosaurs.
Asteroids sized between a small house (like the Chelyabinsk asteroid) and an apartment building (100 meters), which could have dire consequences, will continue to bombard Earth — the smaller and less-devastating ones sooner and more frequently and the larger ones, probably not for several generations.
We might see the danger of asteroid impact, fatalistically, as a matter of chance, like predicting the weather a decade hence. However, this is not so. We should be able to identify and track essentially all of the bodies that will strike Earth catastrophically by observing the night sky with large telescopes — some on the ground, others orbiting in space. Several telescopes are already working on this hunt while they carry out their prime scientific programs; others will carry out this task faster in the future, and some will have to be designed around this central goal.
What if all of this detective work identifies a “mass murderer”? Where and when will it land on the spinning Earth? Fortunately, we would not be playing roulette and can calculate this accurately. Provided that detection is early enough, we should be able to nudge the asteroid off its trajectory and ensure that it misses Earth entirely. This is government surveillance and strategic defense that we can all support.
Yet, overall, progress on finding asteroids that could hit Earth has been far too slow. In 2005, Congress tasked NASA with finding 90 percent of asteroids 140 meters or larger by 2020. The energy released an impact with such an asteroid would exceed that of a 100-megaton nuclear weapon, or roughly 7,000 times the energy of the bomb dropped over Hiroshima. NASA’s inspector general reported in 2014 that the agency estimates it has only found 10 percent of these asteroids and given its current pace and resources it will not meet the goal by 2020.
Is 140 meters even the right goal? An asteroid much smaller, just 45 meters across, exploded in 1908 over Tunguska with an explosive energy of several megatons and destroyed an area as large as New York City. Congress calls these smaller asteroids “city killers,” and although they are 30 times more numerous, we have located less than 1 percent of them.
Part of the reason for falling so far behind target is that planetary defense is currently treated as a scientific issue, and forced to compete with other science missions instead of being seen as a long-term imperative for the protection of humanity and an opportunity for the United States to provide international leadership on a globally important problem.
One way forward is for Congress to direct the National Research Council to follow up on its 2010 study (“Defending Planet Earth: Near-Earth Object Surveys and Hazard Mitigation Strategies”) to determine what additional asteroid search programs in space and on the ground, including other countries, are both feasible and affordable.
The next step would be for a government agency, such as NASA, to carry out an open solicitation to government centers, industry, educational institutions and nonprofits while engaging the international community in order to get the best possible implementation.
Despite its capacity for serious harm, asteroid impact is not the largest existential threat we face right now. Climate change, resource limits, pandemics, nuclear war, societal breakdown, earthquakes and tsunamis are even more alarming. However, in each of these cases there are serious debates about how to proceed, and the path to alleviation is entangled with economic, political, legal and social complications. What distinguishes the asteroid threat is that mitigation is seemingly straightforward, relatively cheap and an activity in which every nation should be able to participate fearing only the consequences of inaction instead of those of action.
I do not know if Mr. Serskov has or will have grandchildren, but I hope he does and that they can grow into a world that will have learned how to respond to these frightening ultimatums. Working proactively and internationally to prevent serious asteroid impact is a good step along the path.
Roger Blandford is a professor of physics at Stanford University and was the first director of the Kavli Institute for Particle Astrophysics and Cosmology. In 2008-2010, he chaired the National Academy of Sciences Decadal Survey of Astronomy and Astrophysics. His email is rdb3@stanford.edu.
