The Solar System is a violent place; debris leftover from the formation of the Solar System is constantly hitting planets and moons, creating impact scars called craters. On planets that are geologically active, like Earth, impact scars gradually erode away with time due to the action of wind, water, and/or lava. Nevertheless, there are some craters on Earth that date back billions of years. The surface of Venus is also covered with impact craters but, unlike Earth, there are almost no craters older than 500 million years. Venus's entire surface seems to have been wiped clean in a catastrophic global-scale event. What could have caused this? For more on Venus click here.