Geological Chronicle
Dominating the rugged southern highlands of the Moon, Tycho is an 86-kilometer impact crater that represents the youngest major geological landmark on the lunar near side. Formed approximately 108 million years ago during Earth's Cretaceous period, the impact carved a fresh, steep-walled basin whose high-albedo ejecta remains visible to the unaided human eye during a full Moon.
The crater is defined by a colossal ray system extending over 1,500 kilometers across the lunar surface, crossing multiple maria and older cratered highlands. Its terraced inner walls drop 4.8 kilometers deep to a floor covered by impact melt sheets and fractured domes. At the center of the crater, a steep central peak rises 1.6 kilometers above the floor, composed of pure crystalline anorthosite uplifted from deep within the lunar crust.
In January 1968, NASA's robotic Surveyor 7 touched down roughly 29 kilometers north of Tycho's rim, becoming the only Surveyor lander sent to the lunar highlands. Its alpha-scattering spectrometer provided the first on-site chemical verification that the bright lunar highlands are composed primarily of aluminium-rich anorthosite rather than basaltic mare rock.
During the Apollo 17 mission in December 1972, astronauts sampled a light mantle avalanche deposit at the Taurus-Littrow valley, more than 2,000 kilometers away. Isotopic dating confirmed that the landslide was triggered by secondary debris flung from the Tycho impact, pinpointing the crater's age at 108 ± 4 million years. Thermal measurements during lunar eclipses show the crater retains heat longer than surrounding terrain because exposed bedrock cools slower than fine regolith.