When romantic men and lovebirds look at the Moon, they hardly think of what is it. It is widely known to be Earth ‘s satellite. But the scientists still think it’s full of mysteries. What is the Moon, where did it come from? Did it appear from the same primary stardust cloud as the Earth did? Or may be it had been torn from our planet long ago? Or may be it had arrived from another galaxy?
To choose the right hypothesis from all suggested, the scientists first have to find out what the Moon consists of. They seem to have answered this question long ago. Samples of moon soil have been delivered to Earth about 20 years ago and have been thoroughly examined. However, the science doesn’t stand still and new research technologies allow obtaining new results.
The scientists from RAS Moscow Institute of Ore Deposit Geology, Petrography, Mineralogy and Geochemistry headed by Oleg Bogatikov, PhD (Geology and Mineralogy), have in details studied Moon soil samples delivered by “Luna-24” automatic station from the Sea of Crisis.
The samples were regolith – lunar sand, forming on the Moon after rocks’ decomposition. The sand particles were very small, about one fourth of mm in diameter. Such small objects were observed first by means of common light microscope, and then by scanning electron microscope equipped with an energy-dispersing spectrometer.
Regolith is able to give the most full idea of what minerals the Moon consists of, because it comprises small particles of various minerals. That may be the reason Russian scientists find so many new minerals in Moon soil. The American stations have delivered thrice as more Moon soil (1500 kg against our 500 kg), but there were almost only large stones. And Russian stations have brought mainly regolith and got their money’s worth.
Delivered samples turned out to have some rare minerals. As a crystallographic rarity the scientists mark a tiny microcrystal of chromous ulvo-spinel embedded into feldspar fragments. This microcrystal has well-defined octahedral shape. The scientists have found one more interesting object – tiny drop-shaped micro particles of native iron, which form almost closed circles.
The most striking thing was that some minerals were discovered for the first time ever! The researchers have found native molybdenum in the moon soil sample – the 1õ0,6 micron-size particle of almost pure molybdenum. It was the first time this mineral was found on the Moon, whether on Earth it never occurs.
Moreover, the scientists have found particles of 0,2-0,7 micron size consisting of iron and tin solid solution. The interesting thing about that is that such mineral never occurs on Earth either, but is widely known as a synthetic compound.
Another discovery is silver sulphide. Its particles were first discovered also as inclusions in feldspar fragments. The authors think that silver sulphide was formed during early stages of the Moon formation, when magmatic processes had been developing in the yet hot planet.
Why does native metals occur on the Moon when they have never been found on Earth? Why metal particles are usually found on the surface of the cuts? The scientists have suggested that it is the result of metal oxides’ reduction by solar wind – proton radiation under conditions of high vacuum and permanent meteorite bombardment. As for the Earth – here metals are just reduced – we have enough water and oxygen for this process.
Another interesting fact is that native metals from the Moon surface are difficult to oxidize. Why does it happen? The scientists consider these reduced metals to obtain amorphous structure under the influence of proton flow, which is much more resistant to oxidizing than crystal structure. To prove their hypothesis the researchers have conducted the following demonstration – they have used a proton beam to write a triliteral word (reported to be “mir” – “peace” in English) on a highly polished molybdenum plate and then have put the plate in the fumes of a very strong oxidizer – aqua regia (nitrohydrochloric acid). In several minutes the word could be clearly seen on the plate surface, which became mat due to corrosion.
Thus, thanks to the Russian scientists, we now know a lot more about Moon soil composition. The researchers have short-term plans for searching Moon soil for platinum compounds or metals of platinum group. Such compounds are widely spread in ancient rocks on Earth, but no one has ever come across them in the moon rocks of the same age. If there are no such compounds in the moon soil, then the hypothesis that the Moon is not the part of Earth, but an independent celestial object, will find confirmation.