Earth-Crossing Asteroids
How can we detect, measure and deflect them?

Less than 50%

Can we do anything about an asteroid that is destined to hit the Earth? The answer is, yes, providing that it is small enough and that we have enough time to send a spacecraft to deflect it. As we will see, the longer the warning time we have, the larger the asteroid we will be able manage. Many of the aspects of asteroid impact mitigation were summarized in the Spaceguard Report. More recently, NASA has also completed a study and is being used by congress to decide what steps the US and other nations can and should take.

Astronomers have spent a lot of time trying to figure out how to save the Earth from an asteroid impact. First you have to find all the asteroids, calculate their orbits and see which ones come dangerously close to Earth. Once you know the orbit, you can figure out when it will hit. This tells you how much warning time you have. And finally, if you can figure out the asteroid’s mass, you can compute how hard you have to push it in order to change its orbit just enough to miss the Earth. Hollywood’s notion of sending a bomb to “blow it up” is unrealistic because present-day launch vehicles can’t carry a big enough bomb. Besides, instead of one large body, you might end up with many small fragments headed toward Earth.

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