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Jan 5, 2022
The discovery of water ice on the Moon on an industrial scale would open up great prospects for its development. Almost all existing projects for the construction of lunar bases provide for the use of local water resources. They are needed in the life support systems of manned stations, and are also required to obtain rocket fuel components. The second part of the article on the resources of the Moon will focus on water, California and, of course, the legendary helium-3.
One of the most unexpected discoveries made during the study of the moon was the discovery of signs of a significant amount of water ice under its surface. And this is in the absence of the atmosphere and traces of water bodies!
The first guesses appeared in 1994 thanks to a radar experiment carried out by the American probe "Clementine". The intensity and degree of polarization of the reflected radio waves recorded by ground-based radio telescopes made it possible to think about the presence of water ice in the region of the south pole of the moon. The authors of the discovery estimated the volume of deposits at about one cubic kilometer.
The studies continued in 1998. The neutron spectrometer installed on the Lunar Prospector spacecraft recorded an increased concentration of hydrogen on the surface near the lunar poles. According to new calculations, the share of water ice in the polar regions could be three to four percent of the mass of the upper soil layer.
More accurate information was obtained in 2009 thanks to an interesting experiment.
In a cloud of dust and gas
The American interplanetary station LRO was launched into orbit around the Moon with the Russian neutron detector LEND, developed and manufactured at IKI RAS under the guidance of Doctor of Phys.-Math. sciences Igor Mitrofanov. Studying the surface, the device indicated that in the area of the Cabeus crater, there may be a particularly large amount of water ice.
To test the hypothesis, it was decided to use the upper stage Centaur, with the help of which the LRO flew to the Moon. It was to become a projectile fired at Cabeo crater for scientific purposes. The idea was that the fall of a heavy structure at high speed would inevitably lead to a flash of light and the ejection of a cloud of gas and dust. And the LCROSS research probe, sent after the Centaur block, flying through the ejected cloud, was supposed to analyze the chemical composition of the material raised from the bottom of the crater. We managed to carry out our plans in full.
As a result of the fall of the upper stage Centaur, an impact crater with a diameter of about 80 m was formed, from which a vapor cloud with a temperature of about 827 ° C rose. Following it, a dust cloud "grew", in which LCROSS was able to detect about 155 ± 12 kg of water in the form of steam.
Fig. 1
Taking into account the estimated total mass of the ejected regolith, the concentration of water ice in the surface layer at the site of the LCROSS fall was estimated at 2.7–8.5% of the mass. Some scientists believe that some of the steam passed the LCROSS sensors and the water concentration in the ground raised by the impact may be even higher.
In addition to water, spectral bands were also observed for a number of other volatile compounds, including light hydrocarbons, sulfur compounds, and carbon dioxide.
According to scientists from the PK Sternberg State Astronomical Institute (GAISh), Moscow State University, the total area of eternally shaded areas in the Cabeo crater, in which water ice accumulates, may be ~ 530 km2 (Fig. 1). Based on these estimates, it can be assumed that the total mass of water ice in the ground of the Cabeo crater reaches ~ 18,000 tons. If this assumption is correct, then the total ice reserves in the south polar region of the Moon can be 100-200 thousand tons.
Ice caps
Over the past decade, the LEND instrument has completed more than 12,400 orbits of the Moon and transmitted more than 110 gigabytes of scientific information to Earth. On its basis, maps of the mass fraction of water in the lunar matter were constructed. Perhaps the main conclusion is that in the vicinity of the north and south lunar poles there are likely to be permafrost regions with a relatively high content of water ice, increasing at some points to several percent of the soil mass (Fig. 2).
Fig. 2
Similar studies were carried out by the Indian spacecraft "Chandrayan-1" with a multispectral scanner, the task of which was to map the locations of various minerals on the lunar surface. With its help, regions of distribution of minerals enriched in hydroxyl and water were discovered (Fig. 3).
Fig. 3
And in the region of the North Pole, in a relatively small area, the researchers found about 40 craters filled with ice. The diameters of these craters range from 2 km to 15 km. Calculations show that the total mass of ice deposits in them can reach 600 million tons.
Ice under your feet
In reality, there may be even more water resources on the moon. As already mentioned, before the launch of the LRO probe, it was believed that the most likely areas of the Moon with deposits of water ice are the so-called "cold traps" - shaded areas at the bottom of craters or depressions where the sun's rays do not fall. It was assumed that water molecules can no longer evaporate from such areas due to the constantly low temperature (about 60 degrees Kelvin, or −213 ° С).
Fig. 4
As a result of generalization of the research carried out with the help of LEND, it was concluded that frozen water can be found not only in "cold traps", but also on the normal surface of the Moon illuminated by the Sun. This was indicated by the weak emission of neutrons, which most likely indicates the concentration of hydrogen. This result was unexpected: it was believed that areas with a high content of hydrogen, and therefore ice, should coincide with the eternally shaded areas in the vicinity of the lunar poles.
Fig. 5
Trying to understand the metamorphosis, scientists looked closely at the photographs taken earlier during the lunar missions, in particular the Soviet "Lunokhod-1" (Fig. 4). It turned out that the loose, rough structure of the relief creates shadow micro-areas that can occupy up to half of the Moon's area. These "patches" of the lunar surface, most likely, hide ice in their shadow from heating by the rays of the Sun (Fig. 5).
Not only comets
For several years now, the discussion of options for the origin of lunar water ice has been going on. The initial versions - that water got to the moon with comets - are gradually being supplemented by more complex ones, which take into account the processes of interaction at the molecular level of the lunar surface with the surrounding space.
According to one of the modern hypotheses, water could be formed not only with the help of comets, but also by combining hydrogen atoms brought with the solar wind with oxygen, which is part of the lunar minerals. As a result of such a compound, hydroxyl could be formed (it consists of an oxygen atom and a hydrogen atom and resembles a water molecule - Ed.). Then the energy released by the impact of meteorites could contribute to the conversion of hydroxyl into water in the form of microscopic deposits of water ice.
Rarity in the Universe
The interaction of the solar wind and other types of cosmic radiation with the surface material of the Moon may present another surprise to earthlings.
In the description of the developments that are supposed to be included in the program of the China National Space Administration (CNSA), another truly unique material is mentioned. We are talking about California (Cf) - a radioactive chemical element. This metal is the most expensive in the world: the price of one gram reaches $ 30 million. Californium is used for scientific research and in medicine. Despite the high cost, the economic effect from the use of this rare metal covers the costs of its production.
On Earth, californium (isotope 252) is created in nuclear reactors by fissioning products irradiated with radioactive plutonium, curium, or neutrons. The essence of the production of this metal lies in the repeatedly repeated stages of decay and transformation of the initial element into an intermediate state - an isotope of another element.
Fig. 6
Chinese scientists suggest that californium can form on the lunar surface in natural conditions (Fig. 6). In their opinion, the concentration of californium on the moon is steadily increasing as a result of the bombardment of the surface by protons formed during solar flares.
Extraction of elements like california on the moon is likely to pay off any lunar program. But until the US Congress allocated funding for the entire Artemis program, and China's planned costs for a manned lunar program are not advertised, it is almost impossible to reliably estimate the cost of mining California on the Moon and delivering it to Earth.
But what about helium-3?
We should also recall the “legendary” helium-3, the “hero” of publications popular 10-15 years ago about saving mankind from energy hunger. It was supposed to be used as fuel in thermonuclear reactors in order to generate electricity for the entire Earth. It must be admitted that the efficiency of such a power plant would be really great. In addition, a helium-3 fusion reactor would be safer than a traditional one.
The problem, however, is that the temperature required to maintain the reaction with helium-3 is on the order of a billion degrees ... a billion! It is difficult even to imagine technical solutions for creating and maintaining such a temperature.
And as a last argument, it should be noted that the amount of helium-3 that falls on the moon as part of the particles of the solar wind and lingers in the lunar soil is catastrophically small. Its amount, according to the journal "Geokhimiya" (volume 51, No. 12 for 2013), varies from 0.02 mg to 130 mg per ton of surface soil, and it will be very difficult to extract it. Those who are interested in this issue, we can refer to the detailed article by A. A. Petrukovich "The moon and a penny of lunar energy" in the journal "Science and Life" No. 8, 2004.
Lunar reckoning
The stage of exploration of the Moon is far from over, and from the now begun new round of the "Lunar Race" (in which the domestic automatic devices "Luna-25", -26 and -27, and, hopefully, manned expeditions will also take a worthy part), we expect the next discoveries. It happens that in the process of such a search, researchers often find not at all what they originally planned, but something much more interesting. It is possible that the picture of lunar resources attractive to earthlings will look different in a few decades.
For example, you can recall that the main result of Columbus's travels to a new continent (then not yet called America, after the name of his main competitor) was not piles of gold (however, not too large), delivered to the Spanish crown, but the most ordinary potatoes, without which it is difficult imagine the life of medieval Europe in a couple of centuries.
The concept of lunar resources from the science fiction section should move in the coming years into a concrete practical plane. According to experts, the global concept of space exploration and the real use of extraterrestrial natural resources requires allocating up to a third of the total costs for the development of an industrial complex to space science.
Such a level of funding will be unattainable for any country in the world for a very long time. Society has not yet realized the gravity of the impending global problems. As a result, truly vital scientific space programs receive only very limited support, losing out to projects that, from the perspective of the future, can only be seen as petty fuss.
The authors hope that this article will help draw attention to the possibility of using space (in our case, lunar) resources to solve the serious problems that humanity will face in this century. The exploration of the Moon - actually the seventh continent of the Earth - should be a logical continuation of the space expansion that began on October 4, 1957 with the launch of the First artificial Earth satellite.
Credits: Lev Zeleny, Vladislav Shevchenko, Russian space.
Related article:
Moon - Klondike on the surface
https://orbiterchspacenews.blogspot.com/2021/12/moon-klondike-on-surface.html
Related links:
ROSCOSMOS Press Release: https://www.roscosmos.ru/33766/
Russian space: https://www.roscosmos.ru/tag/russkiy-kosmos/
Moon: https://www.roscosmos.ru/tag/luna/
Images, Text, Credits: ROSCOSMOS/Russian space/NASA/Orbiter.ch Aerospace/Roland Berga.
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