A crater within Schiaparelli shows many layers that may have formed by the wind, volcanoes, or deposition under water. Layers can be a few meters thick or tens of meters thick. Recent research on these layers suggests that ancient climate change on Mars, caused by regular variation in the planet's tilt, may have caused the patterns in layers. (wikipedia entry)
A crater is a circular depression likely created by an impact event. On Mars large craters are named after deceased scientists, writers and others who have contributed to the lore of Mars. Small creaters (less than 60km) are named after small towns and villages.