Moon’s surface or how do we judge the book by its cover?
By Saba Naqvi, Sana Aziz, Yulian Androsenko
Wonder why there are dark and white spots on the Moon?
Over 400 years ago, Galileo viewed the Moon using a telescope and saw the Moon surface’s dark and white spots have many plains, valleys, mountains and dead volcanoes. An in-depth analysis of the Moon’s surface helped to determine that the light-colored areas of the Moon occupy 83% of the total lunar surface. The dark colored areas of the Moon cover 17% of the Moon’s surface. When we look at the Moon and see its geological features (dark and light spots), the common questions that come to our mind is how the Moon was formed and what unique geological features do these spots hold. In this research, we will investigate the Moon formation theory, the Moon’s major geological features, the qualitative comparison of the Moon with Earth and then conclude it with the Moon’s overall importance in our lives.
Giant Impact theory
The Giant Impact theory suggests that Mars’ sized body collided with the earth and caused a piece of molten rock to detach 1. This theory is most supported than the other theories because the earth’s spin and the Moon’s orbit have similar orientations. The Moon’s surface composition is similar to the earth 1. The Moon samples indicate that the Moon’s surface was once molten like earth. The Moon has a relatively smaller iron core and less density than earth because of its size proportion.
Figure 1: Giant Impact Hypothesis Credit by Wikipedia
Significant features of the surface and how they are formed
Figure 2: Moon and it’s major geographical features. Credit by NASA/GSFC/Arizona State University
The Moon’s surface is composed of dead volcanoes, craters and lava flow within the Moon’s surface that represents rocks of different composition and ages 2. The main question to answer is how these surfaces were formed. It is estimated that the Giant theory took place 4.5 billion years ago, and eventually, magma began to cool, forming a crust on the top layer 2. Then in 4.3 billion years ago, a largest impact had formed Atkin basin, and eventually, one after another impact formed basins or craters on the Moon. Due to the relatively recently formed crust, the lava comes out from the underneath. The larva spread around the craters and gradually filling them 3. It forms basalt rock, which has a high iron content that appears darker than the surrounding area. These dark patches are known as Maria. The light area in the surrounding is known as highlands 4. The amount of crating indicates the surface age. The highland areas of the Moon are densely cratered than the dark-colored Maria regions 4. The highland rocks are composed mostly of Anorthosite, which is a type of igneous rock that forms when the lava cools down slowly as compared to basalt in the case of Maria 4.
Geology and a qualitative comparison of Earth and the Moon
Moon’s crust is mainly made of the same common rock-forming minerals as found on earth, such as olivine, pyroxene, and plagioclase feldspar (Anorthosite)5. Composite rocks on the lunar surface often appear in the form of breccias, as well as the new minerals that were discovered, such as one named armalcolite, short for Armstrong, Aldrin, and Collins, the three members of the Apollo 11 crew. However, the distribution of the ore and compounds is uneven 6.
The main characteristics of the basaltic rocks with respect to the rocks of the lunar highlands are that the basalts contain higher abundances of iron than earth’s counterparts, and also have lower viscosities. Some of them have shown high content of a ferro-titanic oxide named ilmenite. Which is important for human consumption as this ore is the primary one to produce titanium.
Whereas the highland regions are iron-poor and composed primarily of anorthosite, a rock composed primarily of calcium-rich mineral that is poorly mined, maria are composed predominantly of basalt. These basalts have a high abundance of the mineral ilmenite, which, as described earlier, is one of the most important ores on the Moon. This leads us to a conclusion that if the extraterrestrial mining to start on Moon, maria will be humans primary target for the titanium production.
It is also worth mentioning the KREEP that formed 4.5 billion years ago when the surface of the Moon was a liquid magma ocean. KREEP (K-potassium, Rare Earth Elements, and P-phosphorus)5, is that last part of the ancient magma ocean. These components are not useful by themselves as of now; however, they’re precious scientific material. KREEP is a valuable geological material that proves many scientific theories about formation of the Moon and it makes the task of the dividing the Moon into the geological era an actual prospect.
Our satellite has been recently under many heated debates as more and more people realize that the Moon is in fact, made of money. As a valuable mine, generator, a space lift a base for humans to further expand in space, Moon is the most valuable extraterrestrial object as of now,
Figure 3: Variety of Moon ores. Credit by NASA/David Kring
Significance of the Moon’s geology
Moon’s crust is rich with different elements, such as oxygen, titanium, iron, silicon. Most of these resources come in the form of compounds that would have to be broken down and processed. As an example, ilmenite is rich in titanium dioxide, which, when purified, can be used in multiple ways. One of these uses is making titanium-based alloys that are durable but light and are used in creating space crafts 7.
Figure 4: Concept art of Moon mining by Maciej Rębisz
Helium is a disputed resource that is in abundance on the surface of the Moon. Helium-3 is a stable isotope, completely non-radioactive and potentially economically useful. This resource is trapped in the ore and compounds on the surface of the Moon 8. To extract it, one must bore and extract either ore, compounds or, more likely, the trapped ice water. It is clean energy, but the usefulness and feasibility of such endeavors are still disputed.
To bring it all together, the resources of the Moon’s surface and crust are a conveniently placed abundance. Just like we need titanium for our spaceships and helium-3 for the fuel, the more we invest and explore in the Moon missions, people start to understand more about our rich satellite.
Comparison with Earth
When we compare such different bodies, one must notice the first noticeable difference: the Moon is incapable of supporting life as we know it on its own. This is due to the further differences between our planet and a satellite, such as diameter and mass differences. Another big difference is the lack of the iron core and, therefore, lack of the magnet field on the Moon. Moon is also a satellite that orbits around our planet, instead of orbiting the star-like other planets do.
The more detailed differences would be the lack of organic compounds on the Moon, except for the ice water 9. The Moon is also abundant in the titanium and rare-earth elements due to the crust being made out of other space objects like meteors. The Moon lacks tectonic plates and any volcanic activities.
When we understand the comparison between our planet and our Satellite we can truly appreciate the beauty and a complexity of our planet. It also shows us just how important and interconnected things are in the universe.
The importance of the Moon overall
Earth’s Moon is brightest and massive objects in night sky, which makes the earth more habitable planet by moderating our planet’s wobble on its axis, leading towards relatively stable climate. Moon affects our lives on earth, major points include a tidal activity that helps to generate power, planetary tilt and evolutionary history, including the history of humanity on the planet. It influences our oceans, weather, the hours in our days. Without Moon, nights would be darker, seasons would change 10.
In addition, Moon is responsible for maintaining a stable climate. Moon’s gravitational effect maintains constant inclination degree of rotational axis of the earth, this inclination keeps season’s cycle stable as the earth orbits the Sun. Our natural satellite has been and still continues important for the stability of rotational axis, and consequently, our climate 1.
Overall, Moon is important as it controls ocean, it gives earth stable axial tilt that contains metal deposits needed on earth. The earth’s ground is hard, this pull affects significantly oceanic waters, generating slight movement towards the Moon, producing less obvious movement in opposite direction 11.
How do people apply this knowledge?
Since the time of the Greeks, Moon is capable of having a significant impact on life on earth. There are a lot of conditions/proceedings that must be met for advanced life forms like humans to develop on a planet, analyzing several reasons why the Moon, can be of vital importance for life on earth. Moon acted to absorb many of the asteroids that would have otherwise hit the earth in devastating consequences 10.
Conclusion
In conclusion, the Moon’s surface is covered with light-colored and dark-colored materials. The light-colored materials of Moon represent the highland regions, and they cover 84% of Moon’s surface. The dark areas of the Moon cover 15% of its surface. Moon’s surface has craters, multi-ringed basins, lunar mountains and seas. Since the Moon is earth’s sole natural satellite, and it is known as the brightest object in the sky after the Sun and has a larger rocky body with history that is dominated by volcanism and by the impact of the interplanetary debris.
The surface of Moon is covered with dead volcanoes. The terrae (moon highlands) are mountainous, rough, and highly cratered areas. Astronauts who have landed on the moon report that the highlands are four to five kilometers above the average moon surface elevation. The highland surfaces of Moon are made of Anorthosite, a rock that forms when lava cools. There are many craters on highland areas,this shows that they are an old landform of the lunar surface. The maria regions are low plains of two to three kilometers.
References:
1) NASA. About the Moon: In Depth https://moon.nasa.gov/about/in-depth/
2) Maddison, S. (2019). The Moon Project Craters Https://astronomy.swin.edu.au/~smaddiso/astro/moon/craters.html
3) Surface Properties of the Moon http://www.pas.rochester.edu/~blackman/ast104/moon_surface.html
4) Apollo over the Moon: A view from Orbit (NASA SP-362)https://www.history.nasa.gov/SP-362/ch4.1.htm
5) Kennedy Space Center Lunar Geology (Accessed 27 March 2020)
6) NASA Lunar Petrographic Educational Thin Section Set C Lunar Sample Mineralogy https://curator.jsc.nasa.gov/lunar/letss/mineralogy.pdf Meyer (2003)
7) Donachie, Matthew J., Jr. (1988). TITANIUM: A Technical Guide. Metals Park, OH: ASM International. p. 11. ISBN 978-0-87170-309-5.
8) L. J. Wittenberg, E. N. Cameron, G. L. Kulcinski, S. H. Ott, J. F. Santarius, G. I. Sviatoslavsky, I. N. Sviatoslavsky & H. E. Thompson (1992) A Review of 3He Resources and Acquisition for Use as Fusion Fuel, Fusion Technology, 21:4, 2230-2253, DOI: 10.13182/FST92-A29718
9) Frank Tavares (2018) Ice Confirmed at the Moon’s Poles
10) https://www.nationalgeographic.com/science/space/solar-system/why-does-earth-have-moon-how-does-it-affect-our-planet0/
11) Natural History Museum https://www.nhm.ac.uk/discover/how-did-the-moon-form.html