In 1972 Apollo 17 landed on the moon in the Taurus-Littrow Valley on the eastern rim of Mare Serenitatis. Astronauts Gene Cernan and Harrison Schmitt discovered and sampled unusually coloured soil in the form of glass spheres. These spheres occur in a range of colours, from orange to black and green, and in sizes from ten's to hundred's of micron.
Scientists hypothesize that the spheres are the result of fire fountain eruptions that occurred during the same time period as the bulk of mare basalt extrusion, and that they owe their unique colours to a combination of specific chemical compositions, quench crystallization, and devitrification processes.
Automated mineral analysis has allowed the quantification of mineral and glass components, as well as the textural attributes of glass spheres, on a particle-by-particle basis. Researchers can now directly compare samples collected at various locations and draw conclusions on the geological process responsible for the formation of these unique lunar environments.