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How Apollo expeditions help study the moon
The Apollo astronauts installed seismographs on the moon's surface. The Apollo 17 seismographs were supplemented with a small mortar and fired small charges, which allowed the structure to be measured to a depth of somewhere in the first hundreds of meters. Seismographs installed at this and other landing sites recorded the impact of large meteorites, which allowed to Shine through the lunar interior to a great depth. In addition, these observations helped to discover that the moon occur lentracte. These lootrisone happen under the gravitational influence of the Earth when the Moon passes closest. There were about twenty weak surface lunar tremors with a magnitude of up to 3.5.
Since 2010, the moon has been orbited by the American lunar Reconnaissance Orbiter, which takes pictures of the surface with very high resolution. A group of American geologists began to carefully study the huge arrays of new images. And they found traces of tectonic disturbance: thrusts, sinuous ridges known before. But then it turned out that some of these tectonic formations violate small craters, and this suggests that some of these thrusts and ridges are very young — not older than ten million years. Could lootrisone lead to similar formations? It's unclear. On Earth, the formation of such thrusts is accompanied by earthquakes. It's probably happening on the moon, too.
Finally, as mentioned above, seismographs gave information about how the Moon is arranged inside. The velocities of the longitudinal and transverse waves are converted into densities, which give information about the mineral composition of the planet.
Soviet moon Rovers and American astronauts placed several corner reflectors on the surface of the moon. What is it? If you take a box and cut the corner of it obliquely, and then silver the inner surface and point the beam there, it will reflect exactly in the opposite direction. So the laser beams are sent to the moon from the Earth, and placed there reflectors return them. This makes it possible to measure the distance between the laser on Earth and the reflector on the moon with millimeter accuracy.
With these data, we can identify imperfections of the moon's rotation around its own axis, associated with the gravitational influence of the Earth. The moon is not perfectly round orbit, and slightly elongated, and it seems to be swaying, showing 9% of its reverse side. These swings are called librations. Details libratsii say that in the deep bowels of the moon is not solid, but viscous, molten matter. The most valuable information about the library gives a French corner reflector mounted on "Lunokhod-1". It is located where the librations are most visible, farthest from the center of the moon's visible hemisphere.
Why explore the moon today?
Researchers have been looking for water on the moon. Why is it so important to know about its existence? This information helps to clarify existing hypotheses about the origin of the satellite.
The moon's impact formation model States that there was once a collision between the Earth, which was slightly larger than it is now, and a space object the size of Mars. Some of the hot ejections were caught by the Earth's gravitational field into near-earth orbit. And these very hot particles then joined (accreted) to the moon. Previously, when no signs of water were found, the lack of water was associated with the shock formation. There was even a beautiful term bone-dry-Moon, dry as bone.
Another well — known hypothesis is the joint accretion of the moon and the Earth from one protoplanetary condensation. This idea allows us to assume that the Moon is not impoverished by water.
It would seem that the presence of water on the moon proves the hypothesis of joint accretion. But it's not that simple. If you slightly adjust the models that astrophysicists use to explain how water evaporates or is retained, you can save some water in the big Bang hypothesis. So the debate continues and is fueled by more and more data on the amount of water in lunar soil samples. Moreover, it became possible to study the isotopic composition of hydrogen. Previously, in such micro-quantities it was impossible.
Another open question: why does the moon's reverse side not look like the side facing us? On both hemispheres there are quite a few large depressions, the so-called basins. But on the far side of the moon they are not filled with basalt lavas, unlike the visible side, where the covers of basalt lavas in these depressions, mainly in shock, form lunar seas. Why are there no seas on the other side? There are two versions. According to the first, in some part of the moon magmatic sources were closer to the surface than now. There were eruptions of basalt lavas, which, hardening, became very dense. And little by little the Moon turned to the Earth side, where there were clusters of dense matter. According to the opposite view, the Earth's attraction contributed to the fact that on the visible side the sources of basalt lavas were a little closer to the surface than on the reverse, and the outpourings occurred much more often. Which of these is closer to reality is unclear.
Finally, it is extremely interesting to study new sources of lunar matter. The samples available to geologists are not limited to samples taken by astronauts and automatic stations. It is interesting to explore lunar meteorites. Since the Moon is a relatively small body to fly with her, need speed just more than 2 km/s. some part of matter that broke away from the lunar surface during energetic impact of a large meteorite, gaining such speed and flies away from the moon. Part of these emissions falls into the sphere of gravity of the Earth, and they fall on its surface. Geologists have learned to distinguish between lunar meteorites and those that came from the asteroid belt between Mars and Jupiter. Moreover, at the disposal of scientists there are several dozen meteorites, the composition of which is obvious that they came from Mars.
Return to the moon
Apparently, manned missions to the moon are still relevant. Of course, the political aspect plays a significant role in such decisions. NASA is planning a manned mission to the moon in 2024, and if their plans come true, a woman astronaut will step on the surface of the satellite. At brown University, a team of planetologists in collaboration with astronaut David Scott is developing a plan to land a new ship in the same area where Apollo 15 landed. Will we see something new there if we use the latest technology and scientific methods? In addition, there are places on the moon where new deposits of pyroclastic deposits and other unusual rocks have been found using remote orbital observations and spectroscopy. Such a place is, for example, the Sea of Moscow. If you send astronauts there, they could take interesting samples. But it is necessary that the astronauts were well prepared in terms of the Geology of the moon.
There are also more applied areas. Creation of visited or long-term bases on the moon is discussed. For example, on the far side of the moon, where radio emission from the Earth does not reach, you can install a large radio telescope to survey the Universe without terrestrial interference. In addition, there you can establish a base to collect the ship and equip it with fuel and oxidizer for further flight, starting from the moon to Mars. A good place to place such bases are the polar regions, where the Sun shines very obliquely and there are cold zones of eternal shadow. There, in the regolith, are hidden reserves of water ice. This water can be decomposed into hydrogen and oxygen to be used as rocket fuel and oxidizer respectively. The moon's poles also have places where the sun barely sets, such as mount Malapert. This allows unlimited use of solar energy. The Assembly of ships can be carried out in orbit around the moon.
Humanity is sure to return to the moon, but it needs to carefully consider many details, such as equipping the lunar bases. For example, in addition to mooncars, which will allow astronauts to leave the base for hundreds of kilometers and explore the area, the base should have a rescue system — an aircraft that could in the event of an emergency to get to people and save them. While these are extremely difficult tasks, they are feasible.
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