Descartes Highlands

Descartes Highlands. A rugged, heavily cratered region of the Moon located in the central lunar highlands, southeast of the Mare Nubium and northeast of the Mare Nectaris. It is primarily renowned as the landing site of the Apollo 16 mission, which provided the first geological exploration of the lunar highlands. The area's distinct geology, characterized by hilly terrain and Cayley-type plains, challenged early assumptions about its volcanic origin and reshaped understanding of lunar surface processes.

Geography and Location

The Descartes Highlands are situated in the densely cratered terrain of the Moon's southern central highlands, approximately between the prominent craters Descartes and Albategnius. The region lies to the northwest of the Mare Nectaris basin and southeast of the Mare Vaporum, forming part of the ancient, geologically complex crust. Key features within the area include the Cayley Plains, a smooth plains unit, and the sculpted hills of the Descartes Mountains, which are not true mountains but rather the eroded rim of a large, degraded pre-Imbrian basin. The landing site for Apollo 16 was selected on the Cayley Formation near North Ray crater and South Ray crater, which provided access to both plains and highland materials.

Geology and Composition

The geology of the Descartes Highlands is dominated by two primary units: the Cayley Formation plains and the rugged Descartes Formation hills. Prior to the Apollo 16 mission, these formations were hypothesized by scientists like Harold Urey and Eugene Shoemaker to be of volcanic origin, potentially composed of rhyolite or dacite. However, analysis of returned samples revealed the dominant rock type to be anorthosite and breccia, specifically feldspathic regolith breccia and impact melt breccia. This proved the region's materials were primarily formed by impact cratering from events like the Imbrium and Nectaris basin impacts, not by volcanism. The composition is typical of the lunar highlands, rich in calcium and aluminium with lower abundances of iron and titanium compared to mare basalts.

Apollo 16 Mission

The Apollo 16 mission, commanded by John Young with Charles Duke as Lunar Module Pilot and Ken Mattingly as Command Module Pilot, landed in the Descartes Highlands on April 21, 1972. It was the fifth crewed NASA mission to achieve a Moon landing and the first dedicated to exploring the lunar highlands. The crew conducted three extensive EVAs using the Lunar Roving Vehicle, traversing to sites such as Stone Mountain and the rim of North Ray crater. Key activities included deploying the ALSEP scientific station, conducting a far-ultraviolet astronomy experiment, and collecting nearly 96 kilograms of geological samples. The mission's command module, Casper, also carried out orbital science, including photography of targets like the Schiller region.

Scientific Significance

The scientific significance of the Descartes Highlands stems from the Apollo 16 findings, which fundamentally altered theories of lunar geology. The discovery that the Cayley and Descartes Formations were impact-generated, not volcanic, demonstrated the overwhelming role of basin-scale impacts in shaping the lunar crust. Samples like the "Big Muley" anorthosite provided direct evidence for the magma ocean hypothesis, supporting models of early lunar differentiation. The mission's data refined understanding of lunar stratigraphy, impact crater chronology, and the composition of the lunar primordial crust. Furthermore, observations of South Ray crater's bright rays helped calibrate the rate of space weathering on the Moon.

Exploration and Samples

Exploration of the Descartes Highlands was conducted exclusively by the Apollo 16 crew, who collected a diverse suite of samples during their EVAs. The collection includes breccias like dunite-rich samples, anorthosite fragments, and impact melt rocks, with notable specimens such as "Big Muley" and "Rusty Rock". These samples are curated at the Johnson Space Center and have been studied globally by institutions like the Lunar and Planetary Institute. Subsequent remote sensing missions, including Clementine, LRO, and Kaguya, have provided higher-resolution data on the region's composition and topography, confirming and extending the Apollo findings. The site remains a key reference location for understanding impact processes on the Moon and other terrestrial planets.

Category:Regions on the Moon Category:Apollo program Category:Lunar highlands