Studies of lunar regolith delivered to Earth by the Soviet automatic station (AS) Luna-24 using highly local electron microscopy methods made it possible to obtain data confirming the migration of sulfur during cooling of metal melts during the process of liquation. As a result, local Fe-S concentrates are formed, and part of the sulfur is displaced outward, forming sulfur shells on the surface of the melt droplets. Their formation on the surface is associated with the evaporation-condensation process during the cooling process of iron balls. The resulting sulfur coatings can be preserved if they are preserved in glass or under thin films of silicate condensate.

Исследования лунного реголита, доставленного на Землю советской автоматической станцией (АС) Луна-24, с использованием высоколокальных методов электронной микроскопии позволило получить данные, подтверждающие миграцию серы при остывании металлических расплавов в процессе ликвации. В результате образуются локальные концентраты Fe-S, а часть серы вытесняется вовне, образуя серные оболочки на поверхности капель расплава. Их формирование на поверхности связано с механизмом испарения-конденсации в течение процесса остывания железных шариков. Получившиеся покрытия из серы могут сохраняться в случае консервации их в стекле или под тонкими пленками силикатного конденсата.

A comparative study of impact glasses from the Lonar crater, located on the Deccan basalt plateau, India, and impact glasses from lunar regolith delivered by the Soviet automatic stations (AS) Luna-16 and Luna-24 (Sea of Plenty and Sea of Crises) was carried out. Numerous natural alloys (Cu3Ni2, Ni2Cu and Ni3Cu) that were previously unknown in nature were discovered in the impactites of the Lonar crater and the regolith of the Moon. The discovery of such alloys expands the area of isomorphism in the Cu–Ni system. As a result of a comparison of impactites of the Earth and the Moon, similarities were discovered in the composition, size and morphology of particles of copper–nickel alloys, which may be an indicator of impact processes. One of the possible mechanisms for the formation of Ni–Cu particles was condensation from a gas–plasma cloud. A possible source of material for Cu–Ni alloys was both the impactor material and the target material.

— The lunar regolith delivered to Earth in the 1970s by the Soviet automatic stations Luna-16 , -20 , and -24 , despite the small amount of material, is of great value for science and requires careful study. However, since soil samples have gone quite a long way from the moment of extraction to direct examination, there is a danger of possible contamination of the samples with foreign material, both man-made and terrestrial natural minerals. The probability of contamination of the finest fraction of regolith, the particle size of which is less than 100 microns, is especially high, since their detection is possible only by electron microscopy. Using the methods of analytical scanning electron microscopy in regolith samples, contaminant phases that contaminated the original preparations were found, and the sources of these artifacts were shown. The examples of contamination of regolith samples given in this paper and the methods for their identification will make it possible in the future to more accurately diagnose the phases of lunar origin.

Polycomponent condensate glasses found in nature provide an insight into condensation mechanisms, which are still understood inadequately poorly. Condensate glasses found in the impactites of the Lonar crater contain nanosized inclusions of metallic Fe, Cr, Cu, Zn, Ag, In, Te, Au, Pt, and Bi, along with Fe, Cu, and Zn sulfides. This combination may be indicative either of a brief condensation window for the almost simultaneous condensation of components with so different fugacity or of a possible mechanism of cluster condensation, provided that the condensation temperatures of such clusters are close.

— The Lonar crater (India) is the best preserved and most studied on Earth, formed in basalts, which makes it possible to conduct a comparative study with impact transformations of mineral matter on the Moon and other planets of the Solar System. Comparative studies have shown that impactor material, both on the Earth and on the Moon, is present in impactites not only in a geochemically dispersed form, as previously thought, but also in the form of individual submicron particles distributed in the molten target material. These are particles of native nickel, taenite, and high-nickel kamacite, which, apparently, are the transformed material of the impactor. High-nickel submicron metal inclusions are widespread in the impactites of the Lonar crater, as they were found in all studied preparations made from materials collected from different points along the rim of the crater. The high-nickel particles found in this study are an additional argument in favor of the previously stated assumption about the chondrite type of impactor.

The paper presents experimental data on the impact vaporization of serpentinite. The experiment was carried out on a two-stage light-gas gun at the Institute of Mechanics of the Moscow State University by shooting a copper impactor ( 0.5 g) at a speed of 6 km/s. The vaporized material in the form of a condensate film was analyzed on a scanning electron microscope. The analysis showed that the Mg/Si ratio in the condensate drastically decreased (by 1.8 times) compared to the initial ratio in the serpentinite target. Thus, it is shown that the evaporation of the impact melt of a silicate target is selective: the vapor is enriched in relatively volatile SiO2, whereas relatively low-volatility MgO is more retained in the residual melt. Our data thus suggest that the shock-explosive bombardment during the accretion of the Earth may have shifted the compositions of rocks at the planet’s surface from ultramafic to more acid. An acid trend in rock silicity in the course of accretion is possible if the vaporized matter and/or condensate were accumulated on the surface of the growing planet.

The results of long-term mineralogical studies of the lunar regolith, obtained using analytical scanning and transmission electron microscopy, are presented. These studies revealed 105 mineral phases new for the Moon, 43 of which were discovered for the first time under natural conditions; an electronic link to the final table is given. An example of studying condensate glasses and native molybdenum is presented.

Experimental data on impact vaporization of serpentinite are presented. The experiment was carried out using a two-stage light gas gun with an impact velocity ∼6 km/s. Copper with a mass up to 0.5 g was used as the projectile. Impact-generated vapor in the form of a condensate film was analyzed using a JSM-5610 scanning electron microscope. The analysis showed that the Mg/Si ratio in the condensate decreased sharply (by ∼1.8 times) compared to the initial ratio in the serpentinite target. Thus, it is shown that the evaporation of the impact melt of the silicate target is selective: the vapor is enriched with relatively volatile SiO2, leaving a relatively nonvolatile MgO in the residual melt.

A high-calcium high-temperature condensate is detected in the Earth’s impact Lonar crater for the first time. Its finding confirms in practice the theoretical conclusions made earlier from the experimental results. The high-silica condensate found in the Lonar crater, which is similar to those ones in the Zhamanshin crater and in the lunar regolith, confirms the absence of a correlation between the compositions of the target and the impact condensates. The presence of high-temperature condensate glasses in ring structures may be one of the diagnostic criteria to differentiate between volcanogenic and impact formations.

A 3-µm particle of HgS is found by electron microscopy techniques in studying the lunar regolith samples delivered by Apollo 17. It might have been preserved due to a thin cover of highly siliceous glass, having protective functions. This particle was likely formed from a gaseous phase by the condensation of Hg and S vapors.

Впервые в природных условиях в образцах лунного реголита из Моря Кризисов (“Луна-24”) обнаружен высокотемпературный конденсат в виде двухкомпонентных стеклянных шариков с размерами порядка 200-400 нм, состоящих из оксидного Al-Ca-ядра, покрытого равномерной оксидной плёнкой высококремниевого стекла, содержащего нанометрового размера включения железа. Ранее высокотемпературный конденсат был только теоретически предсказан на основе экспериментов по лазерному испарению.