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Krystyna Nawara

Abstract


THE FIRST RESULTS OF LUNAR ROCKS INVESTIGATIONS

Summary

On 20 July 1969 two Apollo 11 astronauts E. Aldrin and N. Armstrong landed on the surface of Sea of Tranquillty on the Moon. At this site the lunar surface is covered by weakly coherent fragmental material – the lunar regolith which ranges in size from particles too fine to be seen with the nacked eye to blocks more than a meter across. The thickness of the regolith layer ranges from about 3 to 6 metres.
The astronauts collected about 21,5 kg of lunar samples from a tiny fraction of Moon's surface. On 24 July 1969 the first samples of lunar rocks landed on the Earth. The lunar samples were investigated by more than 600 scientists from 10 Countries. From 5 to 18 January 1970 the investigators of lunar rocks took part in a Lunar Science Conference held at Houston, Texas. The results of lunar rocks analysis were presented in more than 140 reports. They concerned following problems: age of lunar rocks, trace elements, aboundance of major elements, stable isotopes, rare gases etc, mineralogy and petrology of lunar rocks, Mössbauer studies, magnetic and electrical properties, other physical properties of rocks and minerals, organic chemistry.
The Apollo l1 lunar samples consist of 4 types of rocks: 1. type A – ferrobasalts, 2. type B – microgaibro, 3. type C – microbreccias, 4. type D – soil or dust.
The ages of lunar rocks were determined by several methods. Soil and breccias give ages of 4,6x109 years. Gabros and lunar anorthosites give similar values. Lunar basalts give age of 3,65x109  years. The age of lunar basalt is the same time the age of Sea of Tranquility which is a great plain covered by basaltic lavas. The uplands which surround Sea of Tranquility are probably anorthositic. The chemical compositions of lunar rocks are quite different than these of rocks of Earth and of meteorites. All lunar rocks have unusually high concentrations of titanium, scandium, zirconium, hafnium, yttrium and low concentrations of sodium. The composition of the soil and breccias is similar to the composition of crystalline rocks but soil is also enriched in nickel, cadmium, zinc, silver, gold, copper and thallium. This enrichment is consistent with the observed occurrence at meteorite material in the soil.
Ferrobasalts are vesicular containing augite, plagioclase, cristobalite, ilmenit and residuum of fayalite and hedenbergite. Microgabbros lack phenocrysts and contain coarse-grained augite, pyromangite, ilmenite, plagioclase.
Microbreccias contain four principal components – angular fragments of basaltic rocks, or their individual minerals, glassy spheres, meteoritic material and a cementing glass. Ferrobasalts fragments in breccia contain more residual glass than individual ferrobasalts.
Lunar soil contains four principal constituents – rooks fragments, breccias fragments, dark magnetic glass and transparent glass of a variety of colors.

 


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