Near-Earth objects (NEOs) are meteoroids, asteroids, and comets whose orbits lie close to -- and sometimes cross -- Earth’s. Impact craters on Earth bear witness to the destructive potential of NEOs. The hazard posed by NEOs has captured the professional attention of not just astronomers but ... geologists, biologists, mission planners, aerospace engineers, and even the United States Department of Defense. The public is increasingly aware that Earth resides within a cosmic shooting gallery. The crash of Comet Shoemaker-Levy 9 into Jupiter in 1994 provided proof that cosmic collisions do occur.