Collapsed volcanoes form large, dark spots on Io's surface, NASA/JPL/USGS One of our greatest frustrations as a science, is we astronomical and planetary scientists can’t do the same kind of experiments that other kinds of scientists get to do. We look at things from millions of miles to billions of light years away and try and understand their inner workings while only being able to see their surface. While astronomers really can’t do anything to improve our situation, our planetary science siblings do get periodic opportunities to fling spacecraft around distant worlds and use gravity to...