Expert opinion

Lunar soil - regolith - covers the entire surface of the moon. It is formed as a result of the long-term, over many millions of years, lunar surface meteorite bombardment of particles of different sizes, from micron to meter, with an average speed of about 20 kilometers per second. That causes crushing of the rock surface, carrying formed debris to different distances, melting of the substance and resulting melt spraying, sintering of loose material in the thickness of the regolith under the influence of shock waves.

Regolith consists of primary igneous rocks fragments, different in different parts of the moon, and the secondary particles arose from shock-explosive substance transformation. The secondary particles are regolith breccias - products of regolith fines sintering, agglutinates - products of loose material fusion, the glass particles - products of complete melting of the substance.

The older the surface, the greater the power of the regolith and the higher the fractional conversion - the maturity degree. That, of course, increases the relative content of secondary particles in the regolith.

Samples of lunar regolith were brought to Earth by three automatic stations "Luna": "Luna-16" (1970), "Luna-20" (1972) and "Luna-24" (1976), and by the missions of Apollo (USA).

This sample of lunar regolith was taken by automatic station "Luna-24" on August 18, 1976. The landing place is at the south-eastern part of the Sea of Crisis (Mare Crisium). The core sample was drilled out from the depth of 2 m. The total weight of the lunar soil delivered to the Earth by the recovery capsule "Luna-24" was 170 grams.

Landing site place is located near the border of large circular basin, which bottom is filled by lava flows of high-alumina, low-Ti gabbro dolerite. Regolith in the landing area is characterized by low maturity, expressed in a predominance of fragments of primary rocks and their minerals and low content of secondary particles.

As for the three pieces presented in this sample, two lighter fragments are primary rocks. They are gabbro, composed of plagioclase, pyroxene, olivine and ore material (ilmenite). The third fragment is formed as slightly bubbly sintered glassy mass representing agglutinate.

August 18, 2004

Doctor of Geological and Mineralogical Sciences

Institute of Geochemistry and Analytical Chemistry named after V.I. Vernadsky (Russian Academy of Sciences).
A.V. Ivanov.