Lunar highlands volcanism implications from Luna 20 and Apollo 16

Journal of Research of the U.S. Geological Survey
By: , and 



Highlands materials sampled at the Apollo 16 and Luna 20 sites represent units of distinctive morphology that are widespread on the lunar nearside. Samples from the Apollo 16 site represent hilly and furrowed materials of the Descartes highlands and Cayley Formation. Materials were collected by Luna 20 from terrain resembling the Descartes terrain. Most photogeologic interpretations of these units favored volcanic origins, but the samples fail to support this interpretation. Luna 20 soil fragments are mainly glassy microbreccia with lithic inclusions of fine-grained hornfels; less than 3 percent of the fragments have textures of volcanic rocks, and most of these are likely crystalline products of impact melting. Apollo 16 soils formed on ejecta derived from a plutonic anorthosite-norite-troctolite suite. The similarity of Luna 20 soils indicates that these too formed as regolith on ejecta of anorthosite-norite-troctolitc composition. Interpretation of the samples from the two locations now suggests that hilly and furrowed terrains, previously thought to be of volcanic origin, are impact ejecta; in view of the plutonic nature of the source rocks and their extensive fusion and metamorphism, it is likely that the ejecta were derived from multiring basins. At one point, the Apollo 16 site, the Cayley Formation is composed of basin ejecta.

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Lunar highlands volcanism implications from Luna 20 and Apollo 16
Series title Journal of Research of the U.S. Geological Survey
Volume 2
Issue 1
Year Published 1974
Language English
Publisher U.S. Geological Survey
Publisher location Reston, VA
Description 6 p.
First page 1
Last page 6
Online Only (Y/N) N
Additional Online Files (Y/N) N
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