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This image overlaps the previous one, and the Lunar Apennines and the crater Eratosthenes can be seen at bottom. Moving up, toward the Moon's south pole, more craters come into view. (These images are oriented so that south is up, to match the view in a telescope). The famous crater Copernicus (93km in diameter) is visible in deep shadow as its eastern rim experiences sunrise. The tallest peaks on its western rim are also peeking up, emerging from the long lunar night. Copernicus has an extensive system of rays that are best seen when the crater is in full sunlight. (See our waxing gibbous moon image.) Rays are caused by debris that is thrown from the crater as the impact occurs. It rains down on the ground, radiating like spokes from a wheel. The scientific name for the debris is allocthonous. The rays are spread over Sinus Aestuum, another smooth region made from hardened lava (Sinus comes from the Latin for Gulf). A trio of interesting craters lies to the south: Fra Mauro (94km), Parry (46km), and Bonpland (60km). They were filled with lava, like the crater Archimedes. Parry is probably the youngest, or most recent impact, because it seems superimposed over the walls of the other two craters. The same is true for Ptolemaeus (153km), one of the moons larger craters. It too has smaller craters strewn around it and inside of it.