#calippus

Mare Serenitatis (right) is Latin for the "Sea of Serenity." It is about 419 miles across. Both the Soviet mission Luna 21 and the American mission Apollo 17 landed in this sea in 1973 and 1972, respectively.

Mare Imbrium (left) is Latin for the "Sea of Showers." It is about 712 miles across. The Soviet mission Luna 17 landed here in 1970 and deployed the first robotic rover. The American mission Apollo 15 landed here in 1971, letting Americans spend 3 days on the Moon. More recently, the Chinese mission Chang'e 3 landed here in 2013.

These lunar seas are split by the Montes Caucasus mountain range named after the Caucasus Mountains on Earth.

Within this mountain range are two craters. Calippus crater is named after the Greek astronomer and mathematician Callippus (c. 370 - 300 BC). He made careful measurements of the lengths of the seasons. Nearby is Alexander crater, named after none other than Alexander the Great (356 - 323 BC).

Nearby in Mare Imbrium, Cassini crater is named after the Italian astronomers Giovanni Cassini (1625-1712) and his son Jacques Cassini (1677-1756). They both made strides in astronomy, observing Saturn, Mars, and Jupiter.

Theaetetus crater is named after the ancient Greek mathematician Theaetetus of Athens (c. 417 - 369 BC). He contributed to the study of irrational numbers.