Dr. Morrison: Our nation’s response to the impact hazard has been focused on the Spaceguard Survey, which was urged by congress and was adopted formally by NASA in 1998. It is a telescopic survey to find the majority – the goal is 90 percent – of the near-earth asteroids one kilometer or larger in diameter, because that is the size-range at which you risk a global climate consequence if one hits. So these are the most dangerous asteroids, and fortunately, since they’re moderately large, they are also the easiest for astronomers to find.
NTB: Suppose, just for the sake of argument, we discover that an asteroid is on track to collide with the Earth. Do we have the technology to prevent that from happening?
Dr. Morrison: Asteroid collisions are the only major natural hazard that we can imagine completely negating. You couldn’t stop an earthquake from happening. You can’t stop a volcano from erupting. But in principle, at least, we could stop an asteroid from hitting us. The primary issue is the amount of warning time. The mantra for Spaceguard is “Find them early, and find them early, and then make sure you find them early.”
Given several decades of warning, I have no doubt that we have the space technology and could develop the specific techniques to deflect an asteroid. But given only a few years of warning, we do not have the technology. The best we could do, which would still be important, would be to evacuate the area where the impact was going to take place.
NTB: And we can accurately predict where that will happen with current technology?
Dr. Morrison: When you find one of these objects, initially the orbit is quite uncertain. As time goes on and you do more observations from optical telescopes, and especially from radar telescopes like Arecibo, you refine the orbit and find the probability of an impact. If that probability keeps getting higher as the observations get better, you begin to be concerned. As to pinpointing the actual spot where it would hit, you might have only a few weeks warning at that level.
NTB: Does the technology you’re working on now to assess the hazards of asteroid impacts have any other potential commercial applications for the future?
Dr. Morrison: If we ever develop a robust infrastructure in space with lots of spaceships going back and forth and humans on the Moon and Mars, then there will be a very great need for space resources. Asteroids are the best potential sources of resources. In particular, a lot of asteroids contain water, which is just what you need – as water, as oxygen, as hydrogen – to support humans, to provide fuel for spacecraft. So understanding the asteroids, even learning to move them around, may ultimately be a key to developing a self-sustaining infrastructure in space.
But we aren’t there yet. The immediate issue is whether we can protect ourselves from asteroids. The long-term issue is learning to use this knowledge to provide raw materials to develop a space economy.