Until the emergence of modern astronomy in the 1500s and 1600s, comets remained mysterious and frightening signs of disastrous or extraordinary events. The noted Protestant leader Martin Luther, who died in 1546, stated the common view.
Up until about the middle of the twentieth century, astronomers still possessed an imperfect notion of how and where asteroids and comets originally formed. The theory that asteroids were the remnants of the explosion of an ancient planet still prevailed.
In this brief description of a comet floating in the distant Oort Cloud, Levy makes reference to the object's composition, its size, and its orbit, three of the four major vital statistics, so to speak, of comets. The other is the shape of such bodies.
Until the 1980s, most theories about the composition and other physical characteristics of asteroids and comets could not be verified because no one had ever seen one of these bodies up close. Astronomers who studied them had to rely on images taken by ground-based telescopes.
The idea of mining the planets, Moon, asteroids, and comets for their valuable mineral resources is not new. Science fiction writers began weaving tales of space mines, worked by crusty, usually antisocial old prospectors, in the 1930s.
Mining some of the near-Earth asteroids will exploit the considerable constructive potential of these cosmic bodies. However, many of the NEAs have a darker, more destructive potential as well.