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Near-Earth Objects (NEOs), Asteroids, and Comets: Tracking and Studying Threats to Planet Earth, NASA Spacecraft Missions and Studies (CD-ROM)
World Spaceflight New
Cd-Rom. Progressive Management 2007-04-11.
ISBN 9781422009260
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Publisher description
This up-to-date electronic book on CD-ROM presents a comprehensive library of authoritative federal government scientific documents and publications covering all aspects of the threat posed to Earth by Near-Earth Objects (NEOs), asteroids, and comets. It provides a complete reproduction of the important March 2007 NASA report on NEO Survey and Deflection, an Analysis of Alternatives, plus complete coverage of Potentially Hazardous Objects (PHOs), impact risk assessment, and ongoing projects to detect, track, catalogue, and characterize these objects. There is detailed information about major NASA spacecraft missions studying asteroids and comets: DAWN, NEAR, STARDUST, DEEP IMPACT, and others. Asteroids and comets are the two types of potentially hazardous objects (PHO). For objects in the inner solar system, astronomers can distinguish these bodies on the basis of their appearance. Moving objects that appear as a star-like point of light are known as asteroids. Moving objects that appear diffuse or those that have visible tails are known as comets. People have known about comets since antiquity. The existence of asteroids, however, was not known until about 200 years ago when telescopes became powerful enough to detect the largest such objects. It has taken several generations of improvements in telescope design to detect and understand the small bodies that orbit near Earth. Differences in the appearance of comets and asteroids reflect in part a difference in their composition. Generally, asteroids are relatively rocky or metallic objects without atmospheres, while comets are composed in part of volatiles such as water ice that vaporizes when heated to produce a tenuous and transient atmosphere around the solid nucleus. Comets that are far from the Sun or those that have lost most of their volatiles can look like an asteroid. A volatile-rich object will develop an atmosphere only when heated sufficiently by a relatively close approach to the Sun. The near-Earth a
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Near-Earth Objects
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