Astronomy

Is oxygen really the most abundant element on the surface of the Moon?

Is oxygen really the most abundant element on the surface of the Moon?


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I found this infographic that seems to say that oxygen is the most abundant element on the surface of the Moon. Is this really the case? If so, under what form is this oxygen?


Yes, that's correct; it's also true for the Earth's crust. The reason is that "rocks" are typically made up of components containing combinations of silicon or one or more metals (e.g., magnesium, aluminum, iron) and oxygen, such as silica ($mathrm{SiO}_{2}$); alumina ($mathrm{Al}_{2}mathrm{O}_{3}$); lime ($mathrm{CaO}$); iron oxide ($mathrm{FeO}$); and magnesium oxide ($mathrm{MgO}$).

Examples of common lunar minerals formed from these components includes plagioclase feldspars (mixtures of NaAlSi$_{3}$O$_{8}$ and CaAl$_{2}$Si$_{2}$O$_{8}$), pyroxene (typically XYSi$_{2}$O$_{6}$, where X and Y are metals such as calcium, sodium, iron, magnesium, and aluminum), and olivine (made up of Mg$_{2}$SiO$_{4}$ and Fe$_{2}$SiO$_{4}$), along with oxide minerals like ilmenite (FeTiO$_{3}$). (Source)

Since in all these cases you have between one and two oxygen atoms for every non-oxygen atom, you end up with oxygen as the most abundant single element.


Note this fact is unsurprising. Oxygen is the third most abundant element in the solar system (by mass and by number) after hydrogen and helium.

Planets/moons with the size and escape velocities of the Earth and the Moon are unable to hang onto much in the way of helium- or hydrogen-rich compounds at the equilibrium temperatures at 1 au from the Sun (in fact the presence of quite a lot of water on the Earth is still something of a mystery). On the contrary, even oxygen gas can be retained by the Earth, but more importantly, oxygen is so chemically reactive that it can bond with lots of other things, including other, heavier, but still abundant, elements like silicon, magnesium and iron, to form… rocks.


What Is the Most Abundant Element?

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    The most abundant element in the universe is hydrogen, which makes up about three-quarters of all matter! Helium makes up most of the remaining 25%. Oxygen is the third-most abundant element in the universe. All of the other elements are relatively rare.

    The chemical composition of Earth is quite a bit different from that of the universe. The most abundant element in the Earth's crust is oxygen, making up 46.6% of Earth's mass. Silicon is the second most abundant element (27.7%), followed by aluminum (8.1%), iron (5.0%), calcium (3.6%), sodium (2.8%), potassium (2.6%). and magnesium (2.1%). These eight elements account for approximately 98.5% of the total mass of the Earth's crust. Of course, the Earth's crust is only the outer portion of the Earth. Future research will tell us about the composition of the mantle and core.

    The most abundant element in the human body is oxygen, making up about 65% of the weight of each person. Carbon is the second-most abundant element, making up 18% of the body. Although you have more hydrogen atoms than any other type of element, the mass of a hydrogen atom is so much less than that of the other elements that its abundance comes in third at 10% by mass.


    The Giant Planets

    The two largest planets, Jupiter and Saturn, have nearly the same chemical makeup as the Sun they are composed primarily of the two elements hydrogen and helium, with 75% of their mass being hydrogen and 25% helium. On Earth, both hydrogen and helium are gases, so Jupiter and Saturn are sometimes called gas planets. But, this name is misleading. Jupiter and Saturn are so large that the gas is compressed in their interior until the hydrogen becomes a liquid. Because the bulk of both planets consists of compressed, liquefied hydrogen, we should really call them liquid planets.

    Figure 1: Jupiter. This true-color image of Jupiter was taken from the Cassini spacecraft in 2000. (credit: modification of work by NASA/JPL/University of Arizona)

    Under the force of gravity, the heavier elements sink toward the inner parts of a liquid or gaseous planet. Both Jupiter and Saturn, therefore, have cores composed of heavier rock, metal, and ice, but we cannot see these regions directly. In fact, when we look down from above, all we see is the atmosphere with its swirling clouds (Figure 1). We must infer the existence of the denser core inside these planets from studies of each planet’s gravity.

    Uranus and Neptune are much smaller than Jupiter and Saturn, but each also has a core of rock, metal, and ice. Uranus and Neptune were less efficient at attracting hydrogen and helium gas, so they have much smaller atmospheres in proportion to their cores.

    Chemically, each giant planet is dominated by hydrogen and its many compounds. Nearly all the oxygen present is combined chemically with hydrogen to form water (H2O). Chemists call such a hydrogen-dominated composition reduced. Throughout the outer solar system, we find abundant water (mostly in the form of ice) and reducing chemistry.


    Oxygen

    Oxygen is a colorless, odorless, tasteless gas with a melting point of − 218 ° C ( − 360 ° F) and a boiling point of − 183 ° C ( − 297 ° F). It is the most abundant element in Earth's crust, making up about one-quarter of the atmosphere by weight, about one-half of the lithosphere (Earth's crust), and about 85 percent of the hydrosphere (the oceans, lakes, and other forms of water). It occurs both as a free element and in a large variety of compounds. In the atmosphere, it exists as elemental oxygen, sometimes known as dioxygen because it consists of diatomic molecules, O2. In water it occurs as hydrogen oxide, H2O, and in the lithosphere it occurs in compounds such as oxides, carbonates, sulfates, silicates, phosphates, and nitrates.

    Oxygen also exists in two allotropic forms (physically or chemically different forms of the same substance): one atom per molecule (O) and three atoms per molecule (O3). The former allotrope is known as monatomic, or nascent, oxygen and the latter as triatomic oxygen, or ozone. Under most circumstances in nature, the diatomic form of oxygen predominates. In the upper part of the stratosphere, however, solar energy causes the breakdown of the diatomic form into the monatomic form, which may then recombine with diatomic molecules to form ozone. The presence of ozone in Earth's atmosphere is critical for the survival of life on Earth since that allotrope has a tendency to absorb ultraviolet radiation that would otherwise be harmful or even fatal to both plant and animal life on the planet's surface.

    Oxygen was discovered independently by Swedish chemist Carl Scheele (1742 – 1786) and English chemist Joseph Priestley (1733 – 1804) in the period between 1773 and 1774. The element was given its name in the late 1770s by French chemist Antoine Laurent Lavoisier (1743 – 1794). Its name comes from the French word for "acid-former," reflecting Lavoisier's incorrect belief that all acids contain oxygen.

    Production. By far the most common method for producing oxygen commercially is by the fractional distillation of liquid air. A sample of air is first cooled to a very low temperature in the range of − 200 ° C ( − 330 ° F). At this temperature, most gases that make up air become liquid. The liquid air is then allowed to evaporate. At a temperature of about − 196 ° C ( − 320 ° F), nitrogen begins to boil off. When most of the nitrogen is gone, argon and neon also boil off, leaving an impure form of oxygen behind. The oxygen is impure because small amounts of krypton, xenon, and other gases may remain in the liquid form. In order to further purify the oxygen, the process of cooling, liquefying, and evaporation may be repeated.

    Oxygen is commonly stored and transported in its liquid form, a form also known as LOX (for l iquid ox ygen). LOX containers look like very large vacuum bottles consisting of a double-walled container with a vacuum between the walls. The element can also be stored and transported less easily in gaseous form in steel-walled containers about 1.2 meters (4 feet) high and 23 centimeters (9 inches) in diameter. In many instances, oxygen is manufactured at the location where it will be used. The process of fractional distillation described earlier is sufficiently simple and inexpensive so that many industries can provide their own oxygen-production facilities.

    Uses. Oxygen has so many commercial, industrial, and other uses that it consistently ranks among the top five chemicals in volume of production in the United States. In 1990, for example, about 18 billion kilograms (39 billion pounds) of the element were manufactured in the United States.

    The uses to which oxygen is put can be classified into four major categories: metallurgy, rocketry, chemical synthesis, and medicine. In the processing of iron ore in a blast furnace, for example, oxygen is used to convert coke (carbon) to carbon monoxide. The carbon monoxide, in turn, reduces iron oxides to pure iron metal. Oxygen is then used in a second step of iron processing in the Bessemer converter, open hearth, or basic oxygen process method of converting "pig iron" to steel. In this step, the oxygen is used to react with the excess carbon, silicon, and metals remaining in the pig iron that must be removed in order to produce steel.

    Another metallurgical application of oxygen is in torches used for welding and cutting. The two most common torches make use of the reaction between oxygen and hydrogen (the oxyhydrogen torch) or between oxygen and acetylene (the oxyacetylene torch). Both kinds of torch produce temperatures in the range of 3,000 ° C (5,400 ° F) or more and can, therefore, be used to cut through or weld the great majority of metallic materials.

    In the form of LOX, oxygen is used widely as the oxidizing agent in many kinds of rockets and missiles. For example, the huge external fuel tank required to lift the space shuttle into space holds 550,000 liters (145,000 gallons) of liquid oxygen and 1,500,000 liters (390,000 gallons) of liquid hydrogen. When these two elements react in the shuttle's main engines, they provide a maximum thrust of 512,000 pounds.

    The chemical industry uses vast amounts of oxygen every year in a variety of chemical synthesis (formation) reactions. One of the most important of these is the cracking of hydrocarbons by oxygen. Under most circumstances, heating a hydrocarbon with oxygen results in combustion, with carbon dioxide and water as the main products. However, if the rate at which oxygen is fed into a hydrocarbon mixture is carefully controlled, the hydrocarbon is "cracked," or broken apart to produce other products, such as acetylene, ethylene, and propylene.

    Various types of synthetic fuels can also be manufactured with oxygen as one of the main reactants. Producer gas, as an example, is manufactured by passing oxygen at a controlled rate through a bed of hot coal or coke. The majority of carbon dioxide produced in this reaction is reduced to carbon monoxide so that the final product (the producer gas) consists primarily of carbon monoxide and hydrogen.

    Perhaps the best-known medical application of oxygen is in oxygen therapy, where patients who are having trouble breathing are given doses of pure or nearly pure oxygen. Oxygen therapy is often used during surgical procedures, during childbirth, during recovery from heart attacks, and during treatment for infectious diseases. In each case, providing a person with pure oxygen reduces the stress on his or her heart and lungs, speeding the rate of recovery.

    Pure oxygen or air enriched with oxygen may also be provided in environments where breathing may be difficult. Aircraft that fly at high altitudes, of course, are always provided with supplies of oxygen in case of any problems with the ship's normal air supply. Deep-sea divers also carry with them or have pumped to them supplies of air that are enriched with oxygen.

    Some water purification and sewage treatment plants use oxygen. The gas is pumped through water to increase the rate at which naturally occurring bacteria break down organic waste materials. A similar process has been found to reduce the rate at which eutrophication takes place in lakes and ponds and, in some cases, to actually reverse that process. (Eutrophication is the dissolving of nutrients in a body of water. Growth in aquatic plant life and a decrease in dissolved oxygen are the two main results of the process.)

    Finally, oxygen is essential to all animal life on Earth. A person can survive a few days or weeks without water or food but no more than a few minutes without oxygen. In the absence of oxygen, energy-generating chemical reactions taking place within cells would come to an end, and a person would die.


    The Moon is getting a little rusty. Like, *actually* rusty.

    Of all the things we can say about the Moon, I would never have thought we could call it rusty.

    But new results show that it literally is. Planetary scientists investigating observations made using India's Chandrayaan-1 Moon orbiting spacecraft have found evidence of hematite, a form of iron oxide… or, more commonly, rust.

    More Bad Astronomy

    This really surprised me. For one thing, iron binds with free (that is, not bonded to some other element) oxygen to form hematite in the presence of water, of which the Moon is not overly abundant. Also, what's the source of the oxygen?

    Erlanger crater, near the Moon's north pole, with just its rim lit by low sunlight. Credit: NASA/GSFC/Arizona State University

    But then I saw that the hematite was found mainly at the Moon's poles, which makes sense. At the extreme latitudes near the poles, craters can be deep enough to get very little or even no sunlight their floors are permanently shadowed. In these very cold regions, any water that happens to fall there — say, from an asteroid or comet impacting the Moon, both of which can have lots of water ice in them — will stay there. It's predicted there may be billions of tons of water trapped at the lunar poles.

    OK, great. Water. But what about oxygen? Where does that come from?

    Another surprise: It comes from Earth. Yeah, here. OK follow along: The Earth has a magnetic field surrounding it, something like a bar magnet's. The Sun blows a wind of subatomic particles (the solar wind) that carry their own magnetic field, and when they hit the Earth they distort our magnetic field into a very elongated teardrop-shape. it's very much like a sandbar sculpted by water flowing past sediment in a stream. This feature is called Earth's magnetotail.

    The solar wind compresses Earth’s magnetic field on the side facing the Sun, but creates a long downwind tail on the other side. Credit: NASA

    Also, if you're breathing right now, you know the Earth's air has oxygen in it. In the extreme upper atmosphere the solar wind can pick these atoms up and launch them into space, creating a very thin stream of oxygen flowing along the magnetotail. This tail stretches well past the Moon's distance, and so once a month the Moon passes right through this ethereal flow of oxygen atoms. It really isn't much, but over billions of years it adds up.

    So, wow. Iron + oxygen + water = hematite. Rust. On the Moon.

    To add support to this, they tended to see the hematite on the highest-elevation parts of craters facing toward the equator (so on the north walls of craters near the north pole, and south near the south pole), which is what you'd expect if the flow of oxygen were coming from the direction of the Earth, those parts of the craters face Earth.

    The water part of the equation comes from the ice in the craters, but it needs to be liberated somehow, available to the iron. This, the authors think, occurs when small meteoroids (think gravel and such) hit the Moon's surface. This can blast water molecules up, allowing them to then combine with the iron in the presence of the Earth oxygen flow. Due to the Moon's motion (rotation, orbit around the Earth, and orbit around the Sun) these impacts tend to happen more on the east-facing slopes, and again they see somewhat more hematite in those places.

    Another bit of evidence is that they don't see nearly as much on the Moon's far side, which always faces away from Earth, and, therefore also away from Earth's oxygen stream. So it all hangs together.

    Chandrayaan-1’s Moon Mineralogy Mapper observes the Moon in strips, and the colors here represent different substances: For example water and hydroxyl ions (OH) are blue (note they are near the poles), and pyroxene, an iron-bearing mineral, is red. Credit: ISRO/NASA/JPL-Caltech/Brown Univ./USGS

    They make a testable prediction, too. Oxygen atoms comes in different isotopes, different numbers of neutrons in their nuclei. Oxygen 16 is lighter than O-17 and -18, and so it more easily gets into the upper atmosphere where it can be blown to the Moon. So they predict that hematite on the Moon will preferentially have oxygen-16 atoms in it. Not only that, but we know the ages of many craters, so by checking the abundances of those isotopes in craters of different ages, we can essentially sample what the isotope ratios in Earth's ancient atmosphere were at different times, too. Free science! Very cool.

    The Moon is the nearest object in the entire Universe to us, yet it can still hold many surprises. We can only dig those up (I almost wrote "unearth" ironic in this case * ) by studying it carefully and in different ways. The presence of ice was a surprise when it was first found — it was predicted for decades but very difficult to detect — and it's pretty clear there are a lot more such fun things just waiting for us to find them.

    * Yes, even the word ironic is ironic in this case.


    Splitting Rocks

    To separate the oxygen from other components in faux moon rocks, the researchers use a technique called molten salt electrolysis.

    By first placing the powdery moon dust into a hot batch of molten calcium chloride salt, then running an electrical current through the mixture, the researchers can let chemistry and physics do the heavy lifting. The oxygen previously trapped in the simulated rocks migrates to an electrode (specifically, an anode), where the researchers can then capture it.

    With this technique, the researchers report, they have been able to pull 96 percent of the oxygen out of their imitation moon rocks in the course of just 50 hours. Alternatively, they can extract 75 percent of the oxygen in just the first 15 hours. Plus, as an added bonus, the process leaves behind a mixture of metal alloys that researchers suggest could be useful as well.

    And, just in case you're wondering, according to a press release published last August, researchers at NASA’s Kennedy Space Center are also working on a technique for harvesting oxygen from moon rocks. So stay tuned, because in the not-too-distant future, we might have an old-fashioned gas station bidding war break out on the moon.


    Lunar History

    Figure 2. Lunar Highlands: The old, heavily cratered lunar highlands make up 83% of the Moon’s surface. (credit: Apollo 11 Crew, NASA)

    To trace the detailed history of the Moon or of any planet, we must be able to estimate the ages of individual rocks. Once lunar samples were brought back by the Apollo astronauts, the radioactive dating techniques that had been developed for Earth were applied to them. The solidification ages of the samples ranged from about 3.3 to 4.4 billion years old, substantially older than most of the rocks on Earth. For comparison, as we saw in the chapter on Earth, Moon, and Sky, both Earth and the Moon were formed between 4.5 and 4.6 billion years ago.

    Most of the crust of the Moon (83%) consists of silicate rocks called anorthosites these regions are known as the lunar highlands. They are made of relatively low-density rock that solidified on the cooling Moon like slag floating on the top of a smelter. Because they formed so early in lunar history (between 4.1 and 4.4 billion years ago), the highlands are also extremely heavily cratered, bearing the scars of all those billions of years of impacts by interplanetary debris (Figure 2).

    Unlike the mountains on Earth, the Moon’s highlands do not have any sharp folds in their ranges. The highlands have low, rounded profiles that resemble the oldest, most eroded mountains on Earth (Figure 3a). Because there is no atmosphere or water on the Moon, there has been no wind, water, or ice to carve them into cliffs and sharp peaks, the way we have seen them shaped on Earth. Their smooth features are attributed to gradual erosion, mostly due to impact cratering from meteorites. The maria are much less cratered than the highlands, and cover just 17% of the lunar surface, mostly on the side of the Moon that faces Earth (Figure 3b).

    Figure 3: Lunar Mountain and Lunar Maria. (a)This photo of Mt. Hadley on the edge of Mare Imbrium was taken by Dave Scott, one of the Apollo 15 astronauts. Note the smooth contours of the lunar mountains, which have not been sculpted by water or ice. (b) About 17% of the Moon’s surface consists of the maria—flat plains of basaltic lava. This view of Mare Imbrium also shows numerous secondary craters and evidence of material ejected from the large crater Copernicus on the upper horizon. Copernicus is an impact crater almost 100 kilometers in diameter that was formed long after the lava in Imbrium had already been deposited. (credit: NASA/Apollo Lunar Surface Journal NASA, Apollo 17)

    Today, we know that the maria consist mostly of dark-colored basalt (volcanic lava) laid down in volcanic eruptions billions of years ago. Eventually, these lava flows partly filled the huge depressions called impact basins, which had been produced by collisions of large chunks of material with the Moon relatively early in its history. The basalt on the Moon (Figure 4a) is very similar in composition to the crust under the oceans of Earth or to the lavas erupted by many terrestrial volcanoes. The youngest of the lunar impact basins is Mare Orientale, shown in Figure 4b.

    Figure 4: Rock from a Lunar Mare and Mare Orientale (a) In this sample of basalt from the mare surface, you can see the holes left by gas bubbles, which are characteristic of rock formed from lava. All lunar rocks are chemically distinct from terrestrial rocks, a fact that has allowed scientists to identify a few lunar samples among the thousands of meteorites that reach Earth. (b) The youngest of the large lunar impact basins is Orientale, formed 3.8 billion years ago. Its outer ring is about 1000 kilometers in diameter, roughly the distance between New York City and Detroit, Michigan. Unlike most of the other basins, Orientale has not been completely filled in with lava flows, so it retains its striking “bull’s-eye” appearance. It is located on the edge of the Moon as seen from Earth. (credit: modification of work by NASA NASA)

    Volcanic activity may have begun very early in the Moon’s history, although most evidence of the first half billion years is lost. What we do know is that the major mare volcanism, which involved the release of lava from hundreds of kilometers below the surface, ended about 3.3 billion years ago. After that, the Moon’s interior cooled, and volcanic activity was limited to a very few small areas. The primary forces altering the surface come from the outside, not the interior.


    2 Answers 2

    The composition of the atmosphere, crust, mantle, core and bulk earth are all notably different.

    The atmosphere is composed of

    21% oxygen, with small amounts of other gases.

    The bulk composition of the earth by weight is mostly, iron, oxygen, silicon and magnesium, in that order, with all the other elements making up only about 5% of the earth's weight. Most of the earth's iron is in the core, which is about 85% iron. The rest of the earth is dominated by oxygen and silicon, primarily in the form of silicate minerals, which consist of $ce>$ tetrahedra linked in different ways and with different cations filling in the gaps.


    Chemical Composition

    Of the compounds formed by these elements, silica SiO2 constitutes between 40 and 50% of the Moon's crust by weight, compared to 48.5% in the crust of the Earth. Ferrous oxide (FeO) and calcium oxide (CaO) constitute 10 to 20% of each. All oxidized compounds appear to be present on the Moon only in their lowest states of oxidation, because they solidified at temperatures between 1,100 and 1,200° C (2,000 and 2,200° F). Any free hydrogen on the Moon would be that imported by the solar wind, and water that might be produced by its oxidation would be quickly dissociated by sunlight. A report on lunar data from the 1994 mission of NASA's Clementine spacecraft, however, suggested the presence of water ice. Lunar Prospector, another NASA spacecraft that orbited (January 1998-July 1999) the Moon, was sent crashing into the lunar surface to see if the resulting plume might reveal the presence of water ice, but the results were negative. (The craft bore some of the ashes of planetary scientist Eugene Shoemaker, making him the first person to be "buried" on a celestial body other than the Earth.) If the ice does exist, it lies in the polar regions in permanently shadowed craters. It would be in the form of crystals mixed in with particles of other surface materials, and would constitute a small percentage of this mixture. Such ice might even be sufficiently abundant to support a future lunar colony for some time, if extracting it did not prove prohibitively expensive.

    Mineralogy. The dark crystalline materials that fill the basins of lunar maria can be described as gabbroid basalts - materials akin to lavas known on the Earth but enriched with iron and titanium. In contrast, the continental areas of high reflectivity appear to consist of feldspathic rocks similar to terrestrial granites, including a nearly pure feldspar called anorthosite. Anorthosites replaced the iron or magnesium of basaltic rocks with aluminum, making them lighter in weight as well as color. The very existence of anorthosites on the Moon implies chemical differentiation of the crust, in the course of which heavier elements such as iron were separated from lighter ingredients. Moreover, anorthosites consist mostly of coarse-grained minerals, which means that they must have cooled off slowly from the melt, and thus not on the lunar surface. The dark crystalline materials that fill the basins of lunar maria can be described as gabbroid basalts - materials akin to lavas known on the Earth but enriched with iron and titanium. In contrast, the continental areas of high reflectivity appear to consist of feldspathic rocks similar to terrestrial granites, including a nearly pure feldspar called anorthosite. Anorthosites replaced the iron or magnesium of basaltic rocks with aluminum, making them lighter in weight as well as color. The very existence of anorthosites on the Moon implies chemical differentiation of the crust, in the course of which heavier elements such as iron were separated from lighter ingredients. Moreover, anorthosites consist mostly of coarse-grained minerals, which means that they must have cooled off slowly from the melt, and thus not on the lunar surface.

    The physical texture of the lunar rocks is of even more interest than the chemical composition because of what the texture reveals about the origin of the lunar surface formations. Of signal importance is the fact that 85 to 90% of the material by weight imported from the lunar continents are the breccias. Consisting of grains of various minerals, these are conglomerates of preexisting crystalline rocks, in which angular fragments of diverse origin were welded together by events subsequent to their first solidification.

    The structure of such breccias indicates shock metamorphism (changes brought about by high temperatures and pressures from impact). These kinds of changes indicate, in turn, that the rocks were produced by high-velocity impacts of celestial bodies of different size on the lunar surface in the course of its long history.

    Lunar-orbiting spacecraft have also revealed regions of unusually high gravitational attraction. These regions, called mascons (for mass concentration), are primarily found beneath most of the maria. They are believed to be local concentrations of deeply buried fragments of dense material either from the impacting bodies that initially created the maria or from igneous (volcanic) rocks brought from the molten interior during the lava flooding of the maria.


    This Marvelous Machine Splits Moon Dust Into Oxygen and Metal

    Like the settlers of old, space explorers will live off the land. But if self-sufficiency on Earth is difficult, it’s orders of magnitude more challenging in space, where there are no trees to build shelter, no plants and animals to eat, no water to drink, and no breathable air.

    Like The Martian’s Mark Watney, future space explorers will have to use a heavy dose of science-y resourcefulness to survive hostile environments on the moon and Mars. Luckily, also like Mark Watney, they’ll have access to some of the brightest brains on the planet.

    Some of those brains, currently working at the European Space Agency, are making a machine that transmutes moon dust into oxygen—to breathe and make rocket fuel with—and metal for building.

    Moon Dust Is Nearly Half Oxygen

    Truly, the surface of the moon is a barren wasteland. It’s like being exposed to the vacuum of deep space with the modest benefit of a little ground under your feet and dust on your boots.

    It’s this dust, fine, grey, and bone dry, that may prove to be an invaluable resource for lunar homesteaders. Known as lunar regolith, moon dust is 40-45 percent oxygen by weight. Bound up in mineral and glass oxides, oxygen is the most abundant element on the moon’s surface.

    Oxygen is also, obviously, necessary for breathable air, and it’s a key ingredient in rocket fuel—but you can’t breathe or fuel ships with moon dust. Which is where ESA comes in.

    Performing Lunar Alchemy

    The ESA team, led by University of Glasgow PhD candidate and ESA researcher Beth Lomax and ESA research fellow Alexandre Meurisse, is adapting an industrial method developed by UK company, Metalysis.

    Called molten salt heat electrolysis, the process involves heating up a basket of simulated moon dust—which is a close approximation to the real thing—and calcium chloride salt to 950 degrees Celsius. The researchers then split off the oxygen with an electric current, leaving behind a pile of metal alloys.

    The process can separate 95 percent of the oxygen in 50 hours, but in a pinch, 75 percent can be extracted in just the first 15 hours.

    The team unveiled a proof-of-concept last October, which they said was a significant improvement on other similar processes that produce less oxygen or require far higher temperatures. And there’s room for improvement. To that end, the team announced last week they’re setting up a new oxygen plant in the Netherlands to further refine things.

    A key goal is to reduce the temperature. The higher the temperature, the more energy you need. And energy will be in finite supply on the moon. The team doesn’t have a target temperature in mind, Meurisse told Singularity Hub in an email, but they believe they can do better. How much better depends on how lower temperatures affect other aspects of the process (like efficiency).

    Of Ice and Moon Dust

    In addition to oxygen bound up in lunar dust, we know the moon has water. Though the details are still somewhat shrouded in mystery, scientists believe the moon’s water takes the form of ice in permanently shadowed areas at the poles.

    We’ll need water to drink, of course, but we can also separate it into its elemental components, hydrogen and oxygen, by electrolysis. Provided we can get to the moon’s ice, how does the ESA process’s energy requirements stack up to the electrolysis of water?

    Meurisse said the two resources will likely have different trade-offs to consider (though we may well need need both to support a sustainable presence on the moon).

    Because ESA’s process involves high temperatures, it’s very energy intensive compared to water electrolysis which can be done at room temperature. But moon dust covers the entire surface as far as the eye can see. Grab a shovel and bag some up. The moon’s ice, on the other hand, will be rarer and much more difficult to mine, and we aren’t sure of its composition or what kind of processing it’ll require to make it usable.

    There’s also something else to consider—that pile of metal left over once the oxygen has been pulled off and siphoned away. This metal may prove to be a reliable building material, something the ESA team will also look into exploiting in the coming years.

    “Could [the metals] be 3D printed directly, for example, or would they require refining?” Meurisse asked. “The precise combination of metals will depend on where on the Moon the regolith is acquired from—there would be significant regional differences.”

    Next, the team will build a pilot plant that could operate on the moon (but won’t be sent there yet) by the mid-2020s.

    In the longer term, if the technology proves scalable and space-worthy, it could help make the moon into a gas station for spacecraft in Earth orbit and beyond. Manufacturing fuel on the lunar surface may prove more cost-efficient than dragging it up from Earth. Ultimately, explorers may use moon dust to breathe, build, and fuel missions across the solar system.