If you woke up this morning and the newspaper headline screamed Meteor Headed for Earth, you'd think: That's not good. And you'd probably be right. But sometimes a little cosmic bombardment can be just what the doctor ordered. In a study published online in the journal Nature Geoscience, researchers in Sweden say that 470 million years ago, meteor showers might have boosted our biodiversity. The scientists were studying rocks from China and Scandinavia. And they were looking for two things. First, they were counting the number of different clam-like species they could find. Second, they were searching for chemicals that were carried here by meteorites—extraterrestrial chromite, stuff like that. They found that a huge burst of diversification coincides exactly with a time when meteors a mile wide were raining down on the planet.