James L. Green
James L. Green Director, Planetary Science Division, National Aeronautics and Space Administration
Well, that's a good question. It does, of course, depend upon its size. Many of these objects will come in, and that will be very benign. They'll be spectacular, in fact, from a scientific point of view. We'll be really excited because if we can take a spectrum before it comes in and then run over in the desert or wherever it falls -- could fall on an ice sheet -- and then find that debris and then actually take a spectrum and look at what the composition of that is, we can begin to make -- it's almost like nature's sample returned. So, we do want to continue to do that. So from a scientific point of view, we're highly motivated to look for these objects and then follow them through, all the way down to the ground if we can.
When the larger objects are observed, we then have a lot of work to do, in terms of assessing the threat and assessing what problems we might have. And we're working with Homeland Security, we're working with other parts of the federal government, such that we can understand how disasters occur and how we mitigate those, or more likely the case, if this was going to be something immediate, how to evacuate people and make regions that provide a safe haven.
So, that's disaster planning, and we're involved in those activities. Right now, based on our survey, we see no national imperative for this nation to be upset or excited about impending doom.
Some scientists have predicted Earth is about due to get hit by a giant asteroid. In 1908, hundreds of miles of Siberian countryside were leveled when an asteroid the size of a football field reached our atmosphere and caused an explosion more massive than the atomic blast at Hiroshima. Because such massive asteroids tend to crash into Earth once every century, NASA, along with the European Space Agency, has begun taking steps to prepare for another encounter.
Apophis is an asteroid that has been tracked by scientists. If it threatens Earth, one option is to blow it up with a nuclear weapon, but that could just result in a shower of smaller asteroids. Some scientists favor deflating it by pumping out the material inside; the force of the spewing material could alter the asteroid's direction. Another proposal is to place a spacecraft into an orbit that's identical to that of Apophis; the spacecraft would change the gravitational equation, pulling the asteroid away from Earth. The simplest way to avoid Apophis is to launch a spacecraft that will crash into it, throwing it off its course.
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