An asteroid shower thought to have struck the moon and Earth 800 million years ago may have helped trigger Earth's greatest ice ages, a new study finds... ...to learn more about ancient impacts on Earth, scientists investigated the moon, since craters are preserved well in the vacuum of space on the lunar surface. They investigated 59 lunar craters, each about 12 miles (20 km) wide or larger using the Japanese lunar orbiter spacecraft Kaguya. The researchers analyzed when these craters formed by examining the rings of rock ejected from the impacts which created them. Small meteoroids rain down on the...