Abstract：

About 1200 asteroids larger than 1000 meters in diameter follow orbits
around the Sun that bring them close to Earth.  Over the next 30 million
years, about 400 of them will collide with Earth, each delivering an impact
energy greater than the explosion of a million 1-megaton nuclear weapons.
But these bodies also contain vast reserves of metals, ice, and other
minerals that could be used for future large-scale space activities without
the prohibitive cost of launching them from Earth.  In addition, about 250
NEAs are easier to reach, land on, and take off from than the Moon.  We
shall survey current scientific knowledge of NEAs, proposed schemes for
extraction and use of their mineral resources, and the potential
contribution of these resources to meeting the needs of a space-faring
civilization and of those who remain on Earth.