One of the most visible objects on the Moon is the crater Tycho. The crater was named after Danish astronomer Tycho Brahe (1546-1601). It is 85 km in diameter and 4.8 km deep a big hole! To quote Wikipedis "Tycho is a relatively young crater, with an estimated age of 108 million years (Ma), based on analysis of samples of the crater rays recovered during the Apollo 17 mission. This age suggests that the impactor may have been a member of the Baptistina family of asteroids, but as the composition of the impactor is unknown this is currently conjecture. However, simulation studies give a 70 percent probability that the crater was created by a fragment from the same break-up that created asteroid 298 Baptistina;[1] a larger asteroid from the same family may have been the impactor responsible for creating Chicxulub Crater on Earth 65 million years ago (mya), and causing the extinction of the dinosaurs. The crater is sharply defined, unlike older craters that have been degraded by subsequent impacts. The interior has a high albedo that is prominent when the Sun is overhead, and the crater is surrounded by a distinctive ray system forming long spokes that reach as long as 1,500 kilometers. Sections of these rays can be observed even when Tycho is illuminated only by earthlight." Oh,and by the way Tycho is where they find the monolith in 2001 A Space Odyssey.