The Threat from Space
The 174 color dots in these images of Earth are places where meteorites have struck our planet and left a crater as evidence. The craters vary in diameter from less than 8 kilometers (5 miles) across. The largest craters mean that the meteorite that hit the earth must have caused a catastrophe that changed the land, climate, and life of our planet. Today, astronomers are scanning the sky trying to find the next object on a collision course with our planet, in hope of giving us the time we need to do something about it.