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 across to over 160 kilometers 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 object on a collision course with our planet,in hopes of giving us the time we need to do something about it.