But how big does an asteroid need to be to cause major destruction? The new "Impact: Earth!" asteroid impact effects calculator will help you find out. The interactive web tool, developed by a Purdue University research team led by Jay Melosh, allows anyone to calculate the potential damage caused by a comet or asteroid striking the Earth. Users input information into several parameter fields, such as the diameter and density of the object, its angle of entry, and the location where it will hit. The calculator then estimates the impact consequences, providing information about debris distribution, ground shaking, size of the resulting crater, and whether a tsunami will be generated.