Or so researchers worry.
Image: Wikimedia Commons
The graph below, titled "Known Near-Earth Asteroids," is simultaneously both terrifying and a little bit comforting. Problem is, the Y-axis on a hypothetical graph titled "Unknown Near-Earth Asteroids" would definitely extend much, much higher. Either way, we don't have a good deal of knowledge about what to do about potentially Earth-threatening asteroids, anyway.
That much was clear back in February of last year, when a meteor struck Chelyabinsk, Russia. The meteor came, as far as NASA and other groups that track such things are concerned, from nowhere.
The fear now is that a Chelyabinsk-sized asteroid could hit a city in a war-torn or politically tense area, which would be the powder keg necessary to throw a whole region into turmoil. It may seem like a longshot, and it may seem like something not worth worrying about, but John Remo, a Harvard-Smithsonian Center for Astrophysics researcher would beg to differ. Remo just published a paper in the Bulletin of Atomic Scientists that warns that an asteroid impact could easily be seen as an act of war.
Chelyabinsk wasn't the only one—there have been dozens of explosions worldwide since 2000 with a force of more than one kiloton of TNT, all believed to have been caused by asteroid impacts with Earth, and few of them were picked up by global trackers.
"Near Earth Objects pose a dual danger to civilization: not just the possibility of a catastrophic collision with a massive object, but also the chance that a near-Earth object entering the atmosphere might be mistaken for an intentional attack," Remo wrote. "A worry is that [an] unanticipated explosion over a conflicted region might be misinterpreted as an act of war, with serious consequences."
Despite a huge amount of money and effort being poured into near Earth object tracking, progress has been slow. It has been 20 years since the United Nations decided that an asteroid-caused Armageddon is something worth looking into, and roughly 10 years since NASA decided to try to catalog 90 percent of the "extremely dangerous" near Earth objects (the ones with a diameter of at least 140 meters) by 2020. In that time, NASA has registered just 10 percent of those large objects, and has cataloged just one percent of smaller near Earth asteroids.
"That the Chelyabinsk impact occurred without warning should come as no surprise … [research] showed that ground-based telescopes have a blind spot surrounding the sun in which an asteroid approaching the Earth cannot be seen because of the bright sky background," Remo wrote. Roughly 30 percent of all asteroids and meteors would fall into that category, Remo estimated.
"Deep Impact" was a movie, but it was also a real NASA mission to create a crater on a comet. Back in 2005, that spacecraft pushed the Tempel I comet's orbit roughly 10-20 meters off course—not enough to protect Earth if it was primed for impact. NASA now wants to capture an asteroid and move it into lunar orbit, which could give us options if we are able to identify an asteroid that's on course with Earth.
But that's a big if. As Remo writes, NASA has identified most of the asteroids that could "wipe out entire civilizations," but it hasn't been able to catalog the ones that would, say, destroy a city block. Those asteroids, meteors, and comets all impact Earth much more commonly than you'd think, and we aren't even great at detecting what they are once they hit Earth.
The solution here, of course, is to simply get better at identifying and tracking asteroids and to get better at telling the world about the strikes when they happen. An upcoming mission called Sentinel might help on that front. But if Sentinel isn't able to better track asteroids, the next great international incident of war might not be caused by an aggressive regime, but by a misinterpreted celestial object.