Fascinating article over at The Independent discussing a meeting of the world's top scientists in mid-April, where a five-day "war game" was conducted, not against human enemies, but against "an asteroid up to 1,300ft in diameter – big enough to cause epochal damage," and what to do about it because it is no longer a question of "if" but when as they acknowledge "impact is inevitable."
Watching this five-day asteroid war game from the wings were two Americans, one from the scientific world and one from the military. These elder statesmen of what's called planetary defence have been responsible for reminding policymakers that the planet and all life on it have been shaped by big rocks from outer space slamming into it. Dave Morrison was one of the first researchers to suggest that, unlike the dinosaurs made extinct by an asteroid impact, we might be able to defend ourselves.
Former US Air Force Lieutenant Colonel Lindley Johnson was eventually put in charge of Nasa's Near-Earth Object (NEO) division after first suggesting in the 1990s that the Air Force track asteroids. These men, along with all the world's dedicated planetary defenders, are proud (and relieved) that the Big Question has evolved from what if a cataclysm-inducing space rock is aiming for us – we now know an impact is inevitable – to what will we do about it.
While the entire article is a must-read and the results of this "war game" were highly unsatisfactory (spoiler- Earth gets hit despite their best efforts) it is the sheer numbers that are shocking.
....hundreds of thousands of unmapped smaller objects are winging around nearby: apparently, only one per cent of NEOs above 60ft in diameter have been mapped – and because they're harder to find, they're more likely to hit us. Objects as small as 450ft across would cause severe regional damage, and the mapping project has identified only an estimated quarter of them. ....
NEOs are "Near Earth Objects"
To represent the very real damage, biblical in scope, an asteroid can cause, they point to "The last significant asteroid event was one that nobody saw coming. In 2013, a bus-sized space rock blew up in the sky near the town of Chelyabinsk, Siberia, with a force similar to a nuclear bomb. Windows were blasted, and one thousand people went to hospital. Because many drivers in Russia mount video cameras on their dashboards, scientists had a plethora of YouTube images of a streaking light, followed by a blinding explosion in the sky, which they used to pinpoint the object's trajectory. Chelyabinsk gave them another lesson: what even a relatively small asteroid, bursting not on impact but in the air, can do. And they know it's only a matter of time before something like that happens over New York, London, Delhi or Tokyo."
But the exercise ended on a cliffhanger, with a massive, flaming rock closing in on a teeming, impoverished Asian city. Having done the best they could, the planetary defenders hung up their hero lanyards, packed their suitcases, checked out of their hotels and headed for the airport, leaving the planet forewarned.
The above Independent article comes at a time where massive Internet chatter predicting a September 2015 impact event became so prevalent that NASA was forced to respond to calm fears. A spokesman for the organization stated "NASA knows of no asteroid or comet currently on a collision course with Earth, so the probability of a major collision is quite small."
(Photo above - Screen shot from Discovery Channel's Simulated Asteroid Impact)