The recent event in Siberia has given new urgency to a decades old question: Can we stop one of these things or not? The answer depends on several variables ranked in the following order of importance: how much lead time we have, how massive it is, and how it's put together—asteroids and comets vary a lot in composition. Some are icy, some are rocky and/or metallic, there are conglomerates like a cosmic fruitcake, some are self-gravitating piles of rubble.
Given decades of lead time, using existing technology or technology that could be easily developed in 10 years, we could probably divert a dino killer. But not by blowing it up or shoving it somehow—that could simply turn one dino killer into several thousand meteor craters. The more we learn about these fascinating objects, the more we appreciate how incredibly fragile they are. Even the so-called solid ones are likely to be cracked and fissured into hundreds of shards. Some are best described as dust bunnies concealing trainloads of small debris. Shove an asteroid or a comet, even a little, and we might be back to several thousand meteor craters.
Astronomers believe the best way to divert an object, whole and in one piece, given enough lead time, is an idea called a gravity tractor. Planetary astronomer and impact expert Dr. Phil Plait explains:
A gravity tractor is a way of cajoling a hazardous rock into a safe orbit. Instead of landing on the asteroid or pushing it with rockets, you put a massive probe near it. The gravity of the probe pulls on the asteroid, and you can use that as a "virtual tether". The probe has very low thrust rockets that can balance the force of gravity, and the net result is a tractor that never has to touch the asteroid. This is an incredibly weak force, so it takes a long time to nudge the rock into a safe orbit, but if you have a few years lead time, this is a very precise and elegant way of saving the planet.Obviously the resources of every space-faring nation on earth would be engaged if we detected a dino-killer-sized object heading our way. Play around with this impact simulator and you'll see why: It would be the bloody end of civilization as we know it. But the one that hit Siberia this week was tiny by those standards, about 15 to 20 meters across. Not only would the gravity tractor work great on that—less mass for the tractor to have to attract—there are at least two private companies that might be able to do it at little or no cost to the U.S. taxpayer.
Planetary Resources and Deep Space Industries have announced big plans for mining asteroids. And they told me the first step in that process is finding and determining the exact composition of candidate Near Earth Objects. That's not to say that NASA or some other nation's space agency couldn't do it alone. In fact NASA or ESA asteroid and comet experts would be calling the shots, in much the same way CDC specialists might manage commercial production and distribution of a vaccine to a new, deadly disease.
But frankly, if your business is detecting and mining these objects, given years of lead time, you damn well better have the specialized hardware on hand to detect, analyze, and divert a smallish NEO, even one substantially larger than the bad boy that hit Siberia. And if you plan on making a profit at this, you ought to be able to do it faster and cheaper than an underfunded government agency acting completely alone, starting from scratch, which is too often controlled or influenced by elected imbeciles who do not "believe in" government, along with evolution, thermometers or the Big Bang.