Satellite images of Mercury and Mars are used to illustrate craters and generate a discussion about their cause. After comparing those images with one of Earth, students explore the reason for the lack of visible craters on our planet. The abundance... (View More) or lack of water becomes the focal point of this investigation. The role that water plays in obliterating craters is investigated through an activity using sand, marbles and water. The crater discovered beneath Chesapeake Bay is used to illustrate the fact that Earth's oceans conceal impact craters. The URL opens to the investigation directory, with links to teacher and student materials, lesson extensions, resources, teaching tips, and assessment strategies. This is Investigation 2 of four found in the Grades K-4 Module 2 of Mission Geography. The Mission Geography curriculum integrates data and images from NASA missions with the National Geography Standards. Each of the four investigations in Module 2, while related, can be done independently. Please see Investigation 1 of this module for a two-page module overview and list of all standards addressed. (View Less)