Mercury's Caloris Basin . ... Credit Copyright: NASA , JPL , Mariner 10 Explanation: 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 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 . ...