Tycho () is a prominent lunar impact crater located in the southern lunar highlands, named after the Danish astronomer Tycho Brahe. It is around 108 million years old. It is one of the Moon's brightest craters, with a diameter of around 85 km (53 mi) and a depth of around 4.7 km (2.9 mi). To the south of Tycho is the Street Crater, to the east is Pictet Crater, and to the north-northeast is Sasserides Crater. The surface around Tycho Crater is replete with craters of various sizes, many overlapping still older craters. Some of the smaller craters are secondary craters formed from larger chunks of ejecta from Tycho Crater.
Age and description Tycho Crater is relatively young, with an estimated age of 108 million years, based on analysis by NASA's Lunar Reconnaissance Orbiter. This age initially suggested that the impactor may have been a member of the Baptistina family of asteroids, but as the composition of the impactor is unknown this remained conjecture. However, this possibility was ruled out by the Wide-field Infrared Survey Explorer in 2011, as it was discovered that the Baptistina family was produced much later than expected, having formed around 80 million years ago. 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. In absolute mileage terms, Tycho's ejecta field is approximately the same size as the K-Pg impactor ejecta field, and in proportional terms, the only terrestrial feature of comparable size is the Pacific Ocean. Sections of these rays can be observed even when Tycho is illuminated only by earthlight. Due to its prominent rays, Tycho Crater is mapped as part of the Copernican System.
The ramparts beyond the rim have a lower albedo than the interior for a distance of over a hundred kilometers, and are free of the ray markings that lie beyond. This darker rim may have been formed from minerals excavated during the impact. Its inner wall is slumped and terraced, sloping down to a rough but nearly flat floor exhibiting small, knobby domes. The infrared spectrum of pure crystalline plagioclase has been identified on the southeast wall and rim. The floor displays signs of past volcanism, most likely from rock melt caused by the impact. Detailed photographs of the floor show that it is covered in a criss-crossing array of cracks and small hills. The central peaks rise 1,600 meters (5,200 ft) above the floor, and a lesser peak stands just to the northeast of the primary massif. Anorthosite with a very low mafic abundance has been detected in the central peaks. Infrared observations of the lunar surface during an eclipse have demonstrated that Tycho cools at a slower rate than other parts of the surface, making the crater a "hot spot". This effect is caused by the difference in materials that cover the crater.
The rim of this crater was chosen as the target of the Surveyor 7 mission. The robotic spacecraft safely touched down north of the crater in January 1968. The craft performed chemical measurements of the surface, finding a composition different from the maria. From this, one of the main components of the highlands was theorized to be anorthosite, an aluminium-rich mineral. The crater was also imaged in great detail by Lunar Orbiter 5. From the 1950s through the 1990s, NASA aerodynamicist Dean Chapman and others advanced the lunar origin theory of tektites. Chapman used complex orbital computer models and extensive wind tunnel tests to support the theory that the so-called Australasian tektites originated from the Rosse ejecta ray of Tycho. Until the Rosse ray is sampled, a lunar origin for these tektites cannot be ruled out, though tektites are now generally considered to have been produced by terrestrial impact events. This crater was drawn on lunar maps as early as 1645, when Anton Schyrleus depicted the bright ray system.
Names Tycho is named after the Danish astronomer Tycho Brahe. Like many of the craters on The Moon's near side, it was given its name by the Italian astronomer Giovanni Riccioli, whose 1651 nomenclature system has become standardized. Earlier lunar cartographers had given the feature different names. Pierre Gassendi named it Umbilicus Lunaris ('the navel of the Moon'). van Langren's 1645 map calls it "Vladislai IV" after Władysław IV Vasa, King of Poland. And Johannes Hevelius named it 'Mons Sinai' after Mount Sinai.
Satellite craters By convention, these features are identified on lunar maps by placing the letter on the side of the crater midpoint that is closest to Tycho.
Fictional references
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