When the subject of planetary defense appears in the news, there’s the inevitable allusion to the box office hit Armageddon and some mention of the meteor that unexpectedly pierced through the skies over Chelyabinsk, Russia back in 2013. It would seem as if these two examples are the only hooks with which to engage the public in any discussion concerning the threat of near-Earth objects or NEOs. Indeed, before conducting research for this blog, they were my only points of departure, and while I could tell you that Liv Tyler played Bruce Willis’s daughter in the Michael Bay film, I knew next to nothing about comets and asteroids, the real stars of the production. What were they? And more importantly, would we ever find ourselves as desperate as Hollywood once imagined and/or caught completely unawares as was the case for Chelyabinsk?
What surprised me as I began looking into the subject was that my seemingly basic questions are still being teased out by the field’s leading experts. During a recent 9-week program in Athens, Ohio, an international panel under the auspices of Ohio University attempted to begin untangling them, and in the first pages of their final report, I came across the fundamentals I was searching for.
Comets and asteroids, I soon learned, are likely remnants from the solar system’s beginnings some 4.6 billion years ago. Asteroids, however, differ from comets in that they are rocky bodies found orbiting the Sun near Mars and Jupiter, while icy comets lurk in the outer solar system. More specifically, they live in a distant spherical region called the Oort cloud, explains Professor Madhu Thangavelu of USC, who chaired the project in Athens.
“The Oort cloud is so far away that our scopes don’t even see them till they come close to us, and since they are so fast, they pack a wallop like nothing we know,” Thangavelu explains to me via e-mail.
Given their speed and potential for packing a punch, it is perhaps somewhat reassuring to know they exist in far smaller numbers with respect to asteroids, meaning the odds of them catapulting into our planet are, likewise, significantly lower. But that’s perhaps little comfort when one considers we have yet to track roughly a million NEOs that may threaten life as we know it here on the pale blue dot. And if we lack the technology to simply detect most NEOs, it begs the question: do we possess the technology to protect ourselves in case one decides to go rogue?
I ask Lindley Johson, NEO Programs Executive at NASA. When he responds with what he calls “a heavily caveated probably,” I can’t say I’m too terribly relieved. “[I]t will very much depend on how large an object we find to be on an impact path with the Earth and how far in advance we are able to find it.”
When I pose my question to the founding director of the Asteroid Deflection Research Center at Iowa State University Bong Wie, his response inspires a little more confidence. The launch vehicles, spacecrafts, and nuclear explosive devices we already have in our arsenal, he says, could be utilized if there were ever the need. But would everything be ready to go if an asteroid or comet were to be spotted, say, tomorrow? And if so, how and when would these technologies be rolled out?
Megan Bruck Syal of Lawrence Livermore National Laboratory stresses the importance of first detecting and characterizing the orbit of the NEO in question, a task Dr. Johnson’s program would oversee here in the States. In addition to American efforts, many other observatories around the world would play a critical role in this initial stage, says Syal. And if their data indicated that the object indeed posed a threat, three basic strategies could be deployed in attempt to tackle it.
If a collision were imminent, Syal says areas within the object’s trajectory would be evacuated, making efforts a question of civil defense. Another approach, says Syal, is deflection, which would involve changing the asteroid or comet’s velocity so it would fly past Earth. But if the NEO were to appear on our radar with especially little notice, space agencies might be left with a single option: disruption.
So, how does one disrupt an asteroid exactly?
For those sneaky NEOs that creep up on us completely unawares, a “larger-yield nuclear burst” as Syal calls it might be humanity’s last hope. Or in the words of Professor Thangavelu, “we could lob our mightiest bombs…” Essentially, we would attempt to nuke the object before it made its final approach. Of course, launching these weapons would require significant care, lest we shatter the object too close to Earth and suffer from nuclear fallout, warns Thangavelu.
This technique may sound more or less identical to the method of choice in Armageddon, and the fact that no one has cooked up another idea since the film’s release nearly 20 years ago may not inspire much confidence in our overall readiness. Still, one should take stock in Syal’s vision, as she spends a good deal of her waking hours testing out deflection and disruption techniques on sophisticated computer models.
Admittedly, her work could stand to benefit from a better understanding of asteroids and comets and what they’re made up of. “Acquiring detailed geotechnical information on even just one or a few asteroids,” she tells me “would help constrain our modeling efforts.”
And Dr. Johnson agrees that understanding the composition of these objects is paramount to successfully addressing a potential threat. At the end of day, he explains, it would largely dictate what deflection technique was employed. “Is it a coherent enough mass that will stay together after being punched by a kinetic impactor, or will it just break apart with the pieces still headed on pretty much the same trajectory?” In the case that it’s loosely held together, he says a space probe called a gravity tractor could gently nudge it until the object was no longer a threat.
Once a strategy is selected, the response team may need 2 to 3 years of lead time to design and launch a defense mission, says Wie. Thangavelu, however, isn’t as optimistic and even for the sake of my sensibilities, doesn’t bother mincing words.
“If we had things in place to tackle such a threat, we could do this in a matter of months. But since we have none, we might as well pray,” he tells me.
However lovely and interesting it is to talk with Thangavelu, I can’t say I’m utterly pleased by his fatalistic suggestion.
“We, of course, would be unable to do anything about an impactor unless we find it well before it impacts the Earth,” says Dr. Johnson, again stressing the importance of early detection. “Then, since as you know there are no spacecraft or even launch vehicles just sitting around waiting to go on such a space mission, it will take time.”
How much, I ask.
At least two to four years, says Dr. Johnson. One must consider the fact that the spacecraft might travel as long as a year before ever reaching the asteroid or comet and once it got there, it could take several months or another year to change the object’s orbit. All things considered, “it would take a minimum of six years warning,” he tells me, adding that ten would be ideal. He then stipulates that for asteroids larger than a few hundred meters, multiple missions might be necessary, as well as more time.
But in the absence of what Wie calls any “real operational programs,” perhaps it’s best to take Thangavelu’s advice — that is, sit back and cross your fingers. And for all the studies and simulations undertaken, Dr. Johnson confirms that there is indeed “no operational program in place to build and test an asteroid deflection system and have it ready to launch should an impact threat be detected.”
How could this be, I wonder.
“After 10 years of active research for planetary defense,” says Wie, “I have concluded that $1 billion will be sufficient to establish an emergency planetary defense system…”
That seems like a fairly small price tag for a program that could potentially insure our very existence. Why hasn’t such a system been developed yet?
“I suggest you ask the same question to any politicians in Washington DC,” says Wie.
I then turn the question over to Dr. Johnson.
“First, the countries of the world capable of allocating such funds have only recently begun to realize and understand the threat of an asteroid impact,” he explains. “Second, with so many other demands on resources to meet the daily needs of their populations, where do governments prioritize addressing a hazard that may only occur somewhere in the world once in a few hundred years, no matter how devastating the consequences?”
Again, this isn’t the assurance I was seeking, but no matter how limited their resources, scientists aren’t just sitting on their hands and waiting for doomsday. In fact, NASA and the European Space Agency are in the initial stages of planning the AIDA mission, which will involve both asteroid characterization and the very first real-life deflection test. Using a European spacecraft, the agencies hope to analyze the Didymos asteroid and then with an American spacecraft, to nudge the body itself. The mission, however, isn’t scheduled to launch for another several years, and the craft won’t reach the asteroid until 2022. One can only hope that it gets there in time.