As the opening credits roll in the 1998 disaster flick Armageddon, an amateur observer with some serious gear discovers an asteroid the size of Texas (visually!) and immediately calls it in to NASA. That phone call is about the only remotely true-to-life astronomical scene in the movie. The rest of it is, well, entertaining.

But this past week about 30 impact scientists, communications professionals, policy-makers, social scientists, and science reporters came together in Boulder, Colorado, to explore the "what ifs" were a near-Earth object (NEO) to threaten Earth for real.

This diverse group had been assembled by the nonprofit Secure World Foundation on behalf of "Action Team 14," a sub-subcommittee of the United Nations' Committee on the Peaceful Uses of Outer Space (COPUOS). Through AT-14, COPUOS members have been working for several years on the blueprints for an Information, Analysis, and Warning Network — the policies and procedures that would guide world governments and their respective first-responders when and if we learn that a cosmic collision is coming.

This might surprise you, but there is no worldwide disaster-notification protocol of any kind. The closest analogy might be the cooperative early-warning system developed for tsunamis in the wake of the devastating inundation of Sumatra in 2004. But even that falls short of what's really needed, according to a recent assessment.

As it happens, November 8th's flyby of the 2005 YU₅₅ served as a backdrop for the workshop's discussion. Dynamicists have long known that this visit would result in a clear miss, and the event was popularized more for the prospect of just watching it go by than out of nervous concern that dynamicists has somehow grossly miscalculated. Given the great number of close approaches by asteroids in the recent past and future, it seems that the news-media-stoked sensationalism so rampant in past years has quieted.

Still, how should the word get spread, among governments and to the public, on that certain someday when astronomers realize that a sizable space rock has Earth in its crosshairs? That's what the workshop's attendees (yours truly among them) grappled with for two days. We didn't come to any particularly profound conclusions, but we did frame the guidelines for some commonsense responses.

The first thing to appreciate is that although Earth has been and will get clobbered, it doesn't happen very often. Impacts from objects 10 km across, energetic enough to sterilize Earth, or nearly so, are once-per-100-million-year events — a good thing!

Far more likely, occurring perhaps once every 500 years, would be getting hit by something close to 100 feet (30 m) across. That's small in the pecking order of asteroids but still big and energetic enough to cause absolute destruction to a localized area without ever reaching the ground. We actually know about one such event: in 1908, an object of this size exploded in midair over Siberia and managed to decimate a huge tract of wilderness.

"It is virtually certain (probability > 99%) that the next destructive NEO event will be an airburst," asserts Mark Boslough, who models the destructiveness of impacts at Sandia National Laboratories.

The second take-away is that we'll likely have considerable forewarning — years or even decades in advance of a collision. Sure, it's still possible that we'll be blindsided. Three years ago, 2008 TC₃ slammed into the atmosphere over Sudan just 19 hours after its discovery. There wasn't much time to react, but we lucked out because it was no bigger than a car.

Third, the difficulty of pinning down orbital motion accurately means that impact predictions are fraught with uncertainty — and the public doesn't have much patience for uncertainty. An asteroid (or comet) that might seem threatening when first discovered will, almost always, prove harmless after further observation. So will everyday citizens grow tired or indifferent to repeated "false alarms"?

Even though a devastating impact is a low-probability event, the workshop's risk-management specialists — social scientists, not physical scientists — emphasized the need to have well-constructed, well-scripted, and well-rehearsed plans in place that cover everything from damage estimates to notifying the public to wholesale evacuation if necessary. Clear, consistent messaging is a must, as is transparency. None of that "disaster handbook" exists yet, but Sergio Camacho, who heads U.N. assessment, wants to pass on recommendations by 2013.

For more perspectives on the workshop and how we might prepare for a modern-day Big Bang, check out the postings offered by MSNBC's Alan Boyle, by risk specialist David Ropeik, and by planetarium-show producer Carolyn Collins Petersen. As always, feel free to offer your take on all this in the comment area below.