Science is meant to be an unceasing, always-sceptical search for knowledge, so it's not often that scientists can call it a day, declare a problem all scienced out, and move on. But that's exactly what the team counting asteroid craters on Earth are doing.
You might think that it would be easy to find large asteroid impact craters -- after all, we're talking about a hole in the Earth 80km wide. But unlike on the Moon or Mars, where there's no real climate to erode the planet's surface, asteroid craters have this habit of vanishing, thanks to erosion.
There are 128 known craters on Earth wider than 6 kilometres. And, according to a new study due to be published in the September edition of Earth and Planetary Science Letters, anyone searching for others is just wasting time (and research grants). The team from the University of Freiburg says that the number of discovered craters matches up with the number that should exist, based on the rate of impacts, and erosion rates. Since the number of discovered craters and the number of predicted craters matches up (isn't science great!), planetary scientists can wrap it up and move on to the next mystery. [Earth and Planetary Science Letters via AAAS]
Top image: Don Davis