A dangerous game of "cosmic roulette"?

A dangerous game of "cosmic roulette"? - CBS News: "For a long time, astronomers saw the asteroids and comets that come close to Earth as useless debris -- space rocks that blocked our view of distant galaxies. Not anymore. They're now viewed as scientifically important and potentially very dangerous if they were to collide with our planet. The odds of that happening on any given day are remote, but over millions of years scientists believe there have been lots of impacts, and few doubt there are more to come. A former astronaut told us it's like a game of "cosmic roulette," and one mankind cannot afford to lose."