The Moon, our natural satellite, has always been an object of curiosity, study, and poetry. But beyond the verses and photographs from Earth, science continues to unravel its mysteries. One of the most unique aspects is its atmosphere, or rather, what is technically known as lunar exosphereUnlike Earth, the Moon lacks a thick, breathable atmosphere, and what it has is an extremely thin layer of gases that can barely be considered as such. However, this layer is fascinating for its origin and its interaction with space. Furthermore, information about curiosities of the moon It also helps to better understand its context.
In this article we are going to dive into the world of this exosphere: how it is formed, what it is made of, what processes maintain it And even what interesting facts space missions have revealed to us. We'll cover everything, with scientific rigor but also in accessible language so anyone can understand what's really happening around the Moon.
Does the Moon have an atmosphere?
If we understand by atmosphere a dense layer of gases like the Earth's, then The Moon lacks an atmosphere in that classical sense. However, there is a very thin layer of atoms and molecules around it, so light and dispersed that they rarely collide with each other. This layer is called exosphere and is markedly different from the Earth's atmosphere, which is much denser. The comparison between the two is interesting, as detailed in the Moon as a satellite.
To give us an idea, in one cubic centimeter of the Earth's atmosphere there are approximately 100 billion billion moleculesIn the lunar atmosphere, that number drops to about 100 moleculesThat is, it is so empty that it is practically empty space, although technically it has a detectable gaseous composition.
This is largely due to the low lunar gravity. Its escape velocity—the minimum speed a particle needs to escape into space—is just 2.400 m/s (compared to 11.200 m/s on Earth). With such weak gravity, gaseous particles easily escape into space, preventing the formation of a dense and stable atmosphere. The dynamics of this phenomenon can be related to information about storm surges which also affect celestial bodies.
Even though it seems like there is nothing, this very thin atmosphere has a total mass estimated at around 25.000 kg, about the size of a full truck. It's also constantly changing: during the day, the Sun's heat expands it toward the surface, and at night the particles cool and fall back down.
Origin of the lunar exosphere
The origin of this exosphere has been debated for decades. However, recent research conducted by scientists at the MIT and the University of Chicago, coinciding with previous and parallel studies by entities such as NASA, have confirmed that the main culprit is a phenomenon known as impact vaporizationThe connection between impacts and the lunar atmosphere is crucial to understanding its evolution.
What does this mean? Basically, the lunar surface is constantly being bombarded by micrometeoritesThey are as small as grains of dust, but when they impact, they generate temperatures that reach between 2000 and 6000 ° C. These extreme temperatures They vaporized atoms of the ground, which are released and remain floating around the Moon for a time.
A second process called ion spraying or sputtering also contributes. This occurs when charged particles of the solar wind, mainly protons, collide with the lunar surface and tear off atoms, which then become part of the exosphere. Unlike micrometeorites, the solar wind does not vaporize as much heavy material, so its contribution is smaller. This phenomenon is related to the context of missions to the Moon.
The most recent studies indicate that approximately 70% of the lunar exosphere comes from meteorite impactsWhile 30% is due to solar windBoth processes have been able to be studied in great detail thanks to samples from the Apollo program and the use of isotopes of elements such as potassium and rubidium.
What makes up the lunar atmosphere?
Although the lunar atmosphere is minuscule compared to Earth's, Yes, several gases and atoms have been identified in it. Thanks to ground-based spectrometers, space probes, and experiments with Apollo samples, the following components have been detected. The composition of these gases can provide valuable information about events in the sky.
- Helium and Argon: They are the most abundant elements, detected by the Apollo program and other missions.
- Sodium and Potassium: were identified thanks to subsequent ground-based observations.
- Oxygen, Nitrogen, Methane, Carbon Monoxide and Carbon Dioxide: present in traces, probably as a result of impacts.
- Radioactive isotopes of Radon and Polonium: discovered by the Lunar Prospector probe, could come from the lunar interior.
- Water molecules in the form of ice: They are believed to exist in some permanently shadowed polar craters.
The presence of these compounds indicates that the Moon is not completely chemically dead. In fact, it is known that even some water molecules could survive on its surface if they are in cold areas protected from the Sun. Research on these water molecules has implications for understanding different moons of the Solar System.
Influence of space missions
The Apollo missions played a fundamental role in our understanding of the lunar atmosphere. Not only because they brought back samples of lunar soil, but because the instruments and astronauts themselves altered the nearby atmosphere by releasing gases in their exhalations or during extravehicular exits (EVAs). It is estimated that The lunar modules could have locally contaminated the lunar atmosphere with gases equivalent to its total mass, although most of these will have already disappeared.
In addition, more recent missions such as LADEE (Lunar Atmosphere and Dust Environment Explorer) continued the study of this exosphere. This probe, launched in 2013, gathered valuable information to confirm the importance of impacts and sputtering as key processes. It also allowed for observation of density changes during phenomena such as eclipses y meteor showers, confirming the active dynamics of the lunar atmosphere. This dynamic is essential to understanding phenomena such as the Orionid meteor shower.
Even in recent years, NASA has launched missions like Minotaur 5, whose purpose is to study lunar dust and nearby gases with optical laser systems. All of this with the goal of following drawing a clearer picture of the lunar environment, something essential if we ever want to establish permanent bases there. The planning of these bases is linked to research on Mars colonization.
Why is it important to understand the lunar atmosphere?
Studying this faint gaseous layer may seem irrelevant, but it isn't. First, because it helps us understand the dynamic and geological history of the MoonKnowing how micrometeorites and the solar wind have shaped their surfaces gives us clues about the evolution of other bodies without atmospheres, such as asteroids and Martian moons. This analysis is also fundamental to understanding phenomena such as origin of the moon.
Secondly, it is key to future human missionsEstablishing a base on the Moon will require understanding exactly what elements are in its environment, how they react to the passage of time, and how they can interfere with instruments. It can also, of course, help protect astronauts from the solar and cosmic radiation in the absence of a protective atmosphere.
This research contributes to the broader knowledge about space weathering processes in the inner Solar System. What we learn on the Moon can be applied to the exploration of other destinations such as Mars's moon Phobos, or even near-Earth asteroids.
The lunar exosphere, although extremely tenuous, represents a natural laboratory for studying fundamental cosmological processes. Contrary to what was thought in the past, The Moon is not just a dead rockIt's a body that continues to interact with its spatial environment, and it still has much to teach us if we continue to pay attention.
