An international program to protect the Earth from impact catastrophe: Initial steps

Abstract

NASA has recently completed a study of initial steps to deal with possible cosmic impact hazards. It is generally accepted that impacts by Earth-approaching asteroids and comets pose a significant hazard to life and property, with the greatest risk associated with objects large enough to disturb the Earth's climate on a global scale by injecting large quantities of dust into the stratosphere. Various studies have suggested that the minimum mass impacting body to produce such global consequences is tens of billions of tons, resulting in an explosion with energy approaching a million megatons of TNT. The corresponding threshold diameter for Earth-crossing asteroids or comets is between 1 and 2 km. Smaller objects (down to 100 m) can cause severe local damage but pose no global threat; below 100 m most projectiles disintegrate high in the atmosphere. Current technology permits us to discover and track nearly all Earth-crossing asteroids or short-period comets large enough to threaten global catastrophe. As the initial step in any program to deal with this hazard, we require a long-term telescopic search that reaches stellar magnitude 22 in order to achieve a nearly complete census of objects 1 km or larger. Such a program can be carried out with existing technology using an international network of six telescopes of 2–3 m aperture equipped with modern CCD detectors and automatic signal processing capability. If any object threatens impact with the Earth during the next century or so, we can expect it to be identified with a lead time of at least several decades, sufficient to plan an international campaign to deflect or destroy it.