Planetary Asteroid Defense Study: Assessing and Responding to the Natural Space Debris Threat

The threat posed to Earth and Earth-orbiting spacecraft by natural space debris asteroids, comets and meteor streams is examined in an effort to quantify the threat and identify available, low cost mitigation measures. Our study found that the Earth resides in a swarm of natural debris that consists of at least three families of asteroids the Apollo, Aten and Amor asteroids, several short-period comets and at least 11 active meteor streams. The results of recent studies regarding the risk of a significant asteroid or comet impact on Earth are presented. Best estimates indicate the probability of a large impact within the next century is about 1 chance in 10,000. Further, there is a much higher probability of a smaller Tunguska sized impact sometime in the next century. The myriad of potential impact effects are discussed in detail for various impactor sizes. The threat that meteor storms pose to space-borne assets is also discussed.