The image above was taken by the spacecraft messenger as it flew by the planet mercury. the terrain shown in this image is typical for the surface of mercury. there are many circular depressions of various sizes in the scene (the largest one in the upper right part of the image is about 133 km across). these depressions are called and formed when asteroids and comets struck the planet. a. volcanoes b. mountain ranges c. tectonic plates d. impact craters