The Threat from Space
The 174 colored dots in these images of Earth are places where meteorites have struck our planet and left a crater as evidence. These craters vary in diameter from less than 8 kilometers(5 miles) across to over 160 kilometers(100 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 hopes of giving us the time we need to do something about it.