Astronomers at the Planetary Virtual Observatory and Laboratory (PVOL) are appealing for help, after an image taken by NASA's Mario Rana appears to show an object slamming into Saturn.Saturn, like Jupiter, is a gas giant. With their impressive masses, you would expect these giants to attract their share of asteroid impacts. Unlike terrestrial planets, which are usually left with an obvious crater after impact, on gas giants, it is not entirely obvious. With outer layers primarily composed of hydrogen and helium, any trace of an impact can disappear.Astronomers have attempted to model how many impacts take place on the gas...