Mercury's Caloris Basin
Mercury , the closest planet to the Sun , has a surface with so many craters it resembles the Earth 's Moon . The largest surface feature on Mercury is the Caloris Basin, which resulted from a collision with an asteroid . The basin, which is more that 1000 kilometers across, is visible as the large circular feature at the bottom of the above photograph. Similar features, such as the Mare Orientale , are seen on the Moon. The Caloris Basin gets very hot because it is near the “sub-solar point” - the point on Mercury 's surface that is directly under the Sun when Mercury is closest to the Sun .