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concentrated-dark-matter · 3 years

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MARS

The red planet can really catch attention and has been doing so for several hundred years so far, ever since the first people pointed their telescopes at the sky. Apart from its interesting color, its surface can also resemble Earth somehow, which lead to the creation of many, most extravagant theories about how it could be another, inhabited world. My personal favorite is the one proposed by Giovanni Schiaparelli and Percival Lowell at the end of the XIX century. The first one mistook the darker areas of the planet, channeling it with grooves, for canals of artificial origin. This discovery inspired Percival Lowell, who only went further with such an idea- he stated, that an intelligent species of Martians created them for agricultural purposes, meaning carrying melted water from polar caps to equatorial regions, to water their crops, portrayed by darker spots on the planet's surface. After those „discoveries”, scientists of that period thought that contacting Martians is only a matter of time. And although said theories didn’t turn out to be true, their spirit still lives on, as Martians turned out to be one of the most overused tropes in sci-fi history. It certainly has some reasoning towards it, as it’s the closest alien world to us, and shares some traits with earth. At first glance, Mars even seems like it could have the potential of supporting life. Yet still, the mission of the Mariner 4 probe in July of 1965 showed the complete inability of the planet and entirely completely crushed all our hopes for extraterrestrial life of martian origin.

And how so?

Even though Mars is located in a habitable zone, (I talked about it in more detail in my exoplanets and extraterrestrial life post) allowing it to have liquid water and stable surface temperature, it has none. Its surface is like a great, freezing desert, completely dry and unwelcoming.

It is most commonly assumed, that the most important role in the current shape of mars played the lack of magnetosphere. As in the case of the earth, the magnetosphere has a crucial role in shielding life from the deadly solar wind. Contemporary Mars does not have such protection, so any organisms living there would be annihilated immediately. Another important aspect, which leads to Mars’ lifelessness, is the fact, that its gravity is over 60% weaker than the one on earth. Compared to such a planet’s size, it is too weak to maintain a thick layer of the atmosphere, and therefore most of the particles flew away, leaving the red planet with an atmosphere only 1% as dense, as the earth’s one.

Lack of any denser atmosphere had its consequences for the climate. On earth, its thick layers prevent the heat from leaving the planet and milden the surface temperature via the greenhouse effect. Mars, once again, wasn’t lucky enough to develop such a mechanism on its own, and its surface temperatures can change drastically. Although the planet's mean surface temperature is -63C, the rocks, that create the surface heat very quickly when the sun shines on them, and the daily temperature swings can reach even values around 100C.This, in combination with very low pressure, creates very strong winds in some parts of the globe, which result in extremely fierce, and long-lasting dust storms, that can block the sunlight even for months! that doesn’t create dream conditions for the Martians, does it?

In such an unfavorable scenario, ice caps in the polar region seemed like an opportunity- if not for the Martians, then possibly for future space missions. With such surface temperatures though, no greater amounts of water could exist in a liquid form, so we can be assured that Mars is a completely lifeless place right now.

Korolev crater, fully filled by Martian ice

But it hasn’t got to be like that in the past.

The existence of the Tharsis Plateau on Mars gives us a clear sign, that Mars has been geologically active in the past. It consists of five shield volcanoes, with the highest one, Olympus Mons, which is considered the highest volcano known to mankind, with its impressive 21 287,4 m above the surface. Further studies of it revealed that its great height is caused by the fact, that Mars has no tectonic plates- or rather, only a single one, like an orange peel. Geological studies of the rocks on the plateau and past activity of Tharsis’ volcanoes helped scientists understand its geological past, and lead to a revolutionary discovery- over 4 billion years ago, Mars contained liquid water. The evidence for this thesis was supported by Spirit, Opportunity, and Curiosity rovers, which analyzed the Martian soil and rocks from up close. Chemical analysis of the soil showed, that it contains chemical compounds, that could exist only under the influence of liquid water. What’s more, the mysterious martian channels (the ones mentioned in the introduction) have signs of rill erosion, as well as the rovers have found small rocks of oval shape, that also must have got it from water's influence. This leads us to a shocking statement- mars had liquid water in the past, commonly existing on its surface.

hypothetical ocean on Mars

It is certain, that there was a great water body somewhere on the north of Mars from around 3,7 to 2,9 billion years ago, but scientists still can’t figure out how deep it was and how long did it lasted.

Still, all the life forms known to our knowledge started in water and then needed it t further exist; therefore, it is possible, Mars was lucky enough to develop some life forms of its own. Interestingly enough, the oldest fossils of bacteria on earth are dated at 3 billion years, which leads us to another theory. Is it possible, that the freshly developed organisms got transferred to earth with the use of the panspermia method (I talked about what it is exactly in my extra-terrestrial life post) and supported the freshly developed terrestrial organisms, or even were the source of life on earth itself? Many scientists argue about that (back then, there might were too few phosphorates on Mars for DNA to form) and as astrobiology is a freshly developing field, there is no solid evidence proving or disproving that theory, but for sure it could be a possibility. Another thing, that makes this theory hard to acknowledge, is that we don’t know how the mechanism of life beginning to exist went, so there is no way right now, to confirm where it came from if it even came from somewhere.

Still, whatever life forms lived on Mars before, they ceased to exist around the Noachian period in Mars’ history, around 3 billion years ago. As Mars’ gravity is much lesser than Earth’s, the only thing keeping its atmosphere back then, was plate tectonics. As Mars’ core has completely cooled down, volcanism and land-shifting have stopped, and the atmosphere, made mostly out of carbon dioxide, was no longer able to warm the planet. It has also lost its magnetism, and now, thanks to the solar wind, all the water has evaporated, and the molecules making the atmosphere have completely fallen apart. After that, Mars has completely lost its habitability and formed the shape of the lone, red desert we know today.

However, could this process be reversed somehow? Is there a way to make Mars habitable once again?

Many people consider Mars as an emergency solution, in case of any sort of cataclysm or global disaster happening to the Earth, so that it is no longer habitable. In such a scenario, people should move to Mars and start living there, or even send some human colonists there ahead, so the planet is secured in case of crisis. In 2016, Elon Musk said that people will inhabit the red planet in 40 years! An optimistic assumption, if colonization was ever to happen. As we know, Mars in current shape is very unwelcoming and unhabitable. If we were to actually colonize the planet, it would require the process of adjusting Mars’ conditions to our needs and what we have on Earth, meaning t e r r a f o r m i n g.

a vision of terraformed Mars

Terraforming Mars would prove to be a very difficult process. At first, we’d have to raise its surface temperature, and lessen the daily temperature swings. Humanity has, unfortunately, experience in warming up a planet using the greenhouse effect, but such a solution would be useless on Mars. For the greenhouse to work, a planet must have a dense atmosphere. Mars has none. Another way of increasing Mars’ surface temperature would be to detonate nuclear bombs over its polar caps, as an explosion should produce enough heat, to vaporize the frozen carbon dioxide and release it to the atmosphere, only then to use greenhouse warm the planet and melt the water ice. Although it might seem like nuking Mars is a solution, it raises many questions of scientific, legal, and ethical nature. Besides, we are not even sure if such a radical way of terraformation would be a success and leave any significant impact.

There’s also one other important issue: breathing. Mars's atmosphere is composed in 95% of carbon dioxide, and only 0,16% of oxygen. As ISS scientists have discovered, there are kinds of special bacteria, called cyanobacteria, responsible for converting co2 into oxygen during photosynthesis. Machines doing the same thing are also underway, but it will certainly take many years for such inventions to become successful. And even if we had certain methods of converting carbon dioxide into oxygen, it would take hundreds of years, for the bacteria- or machines, to create a nice, breathable atmosphere for the first colonizers.

But even if we manage to somehow overcome all of these difficulties, their effect would probably be short-termed and completely not worth the effort. Why? because Mars has no magnetosphere. Unless we somehow reduce the effect of the solar wind, every molecule we’ll pump into the atmosphere will be destroyed by the solar wind, and the terraformation of Mars would be a never-ending job. Right now, we have no idea how to create an artificial magnetosphere for a planet, but NASA astronomers thought about setting an instrument of a great magnetic field at the point where Mars’ and Sun’s gravities cancel out, to protect the red planet from the solar wind. While we doing such a thing seems like a very intelligent and creative solution, still, the magnetic instrument would require 20 thousand Gauss (units of electromagnetic induction), a force unreachable for contemporary technology.

Therefore, I believe we should cool down a bit on the topic of terraformation. I personally believe it is a very exciting subject, especially from how science and other technologies would develop, but right now, the task of terraforming is way beyond the current scientific and technological capabilities. In this debate of terraformation, we should also consider one important fact.

the water on mars stopped to exist, as the core of Mars has completely cooled down. This fact should give us a reflection, on how fragile is the natural balance of Earth, and how just a small change, can completely ruin the stability and make our planet a deadly desert. Therefore, we should be even more mindful of things happening on earth and possibly threatening is homeostasis, and react quickly if something like that occurs. Apart from seeing Mars as an alternative planet and putting all of our hopes and efforts into colonizing it, we should rather focus on maintaining earth in peace and balance, to live on the planet we are destined to.

bibliography:

Pale Blue Dot: A Vision of the Human Future in Space by Carl Sagan, 1994, translated version

Cosmic Chronicles: A user's guide to the Universe by Fred Watson, 2018, translated version

https://www.nasa.gov/audience/forstudents/postsecondary/features/F_Canali_and_First_Martians.html

https://www.planetary.org/articles/10251246-noachian-hesperian-amazonian

https://www.space.com/can-we-really-terraform-mars

https://www.planetary.org/articles/can-we-make-mars-earth-like-through-terraforming

https://www.nasa.gov/feature/goddard/2019/with-mars-methane-mystery-unsolved-curiosity-serves-scientists-a-new-one-oxygen

https://en.wikipedia.org/wiki/Martian_soil

https://mars.nasa.gov/all-about-mars/facts/

https://science.nasa.gov/heliophysics/focus-areas/magnetosphere-ionosphere

https://en.wikipedia.org/wiki/Climate_of_Mars#Atmospheric_properties_and_processes

image sources:

(https://commons.wikimedia.org/wiki/File:Mars_atmosphere.jpg)

http://www.thegreatcoursesdaily.com/wp-content/uploads/2021/02/Mars-Feature-1024x555.jpg

https://upload.wikimedia.org/wikipedia/commons/7/75/Perspective_view_of_Korolev_crater.jpg

https://upload.wikimedia.org/wikipedia/commons/thumb/9/98/AncientMars.jpg/1200px-AncientMars.jpg

https://upload.wikimedia.org/wikipedia/commons/7/7f/MarsTransitionV.jpg

https://backend.inteligentnisvet.cz/wp-content/uploads/2021/08/mars.jpg

#astro community #astrobiology #astronomy #popular science #sci fi #personal project #the universe #education #Mars #terraform #terraforming #science

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concentrated-dark-matter · 3 years

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EXTRATERRESTRIAL LIFE

“Two possibilities exist: either we are alone in the Universe or we are not. Both are equally terrifying.” Arthur C. Clarke

Whether humans are alone or not in the universe remains one of the greatest mysteries known to mankind. People all around the globe tried to find any signs or proof of alien life throughout history and wondered what is our place in the universe. Extraterrestrial life was the subject studied both of ancient religions, medieval theologians, as well as modern period philosophers and astronomers. For example, the famous 16th-century Italian philosopher Giordano Bruno, who was the first one to state, that there might be many other planetary systems from ours and that they could also contain intelligent inhabitants. His thesis seemed revolutionary back then, but thanks to Copernicus and many space missions we can be sure that our planet isn't made to be the center of the universe. There are around 100 billion planets in the Milky Way itself, so the chance that none of them is occupied by anyone is... well, low.

Right now, many contemporary astronomers tried to look for alien life, by launching programs and campaigns such as SETI (I’ll talk about it in more detail further in this post), aiming for finding any signs, that we might not be alone out there.

Still, even with all of those centuries years worth of effort put into the search for extraterrestrial intelligence, we yet haven’t found sufficient proof, whether it exists or not. But we are searching.

The thing, that for sure complicates our search, is the fact, that we have no idea what extra-terrestrial forms of life may look like. We can't be sure what is necessary for life to occur, because everything that led to its origin on earth, could have gone in completely different conditions in completely another way, hence creating an entirely different outcome. Even if just the process of the forming of life went similarly to the one on earth, the alien life would evolve in completely different conditions from ours, so it could turn out to be far more different from what we know of life.

Still, the assumed extra-terrestrial life will exist in the same universe, where there are the same physical and chemical laws apply, like the ones on earth. Therefore, we know for sure it won’t exist in extremely unstable conditions (like on a star's surface) because the organism would fall apart shortly after its creation, nor in too stable (for example in very cold temperatures, where there is very low to no movement of the molecules), because the organism won’t even get the chance to form.

Then, it has to have some chemical base, like some dominant element, that is the foundation of the organisms. On earth, it’s carbon, and for a good reason. It's really common on our planet, and also can form four, stable chemical bonds with other elements, as well as create big, advanced structures, like chains and rings. Thanks to these properties, carbon seems it could be one of the easiest foundations for other forms of more developed life as well. But not necessarily.

The conditions on some planets might make carbon-based life impossible to exist. Does it then mean that said planets would be fully inhabitable? Not really! Alien life could form here- it would just have to manage with completely different elements. Most probably, it would then use silicon. Why? Well, it displays similar properties as carbon does (as they are in the same group in the periodic table, and silicon can also create stable quadruple bonds), and it could withstand much higher temperatures. It is also a pretty common element on earth, so if the planet's conditions weren't completely extreme, it could also be as often there. If it only had the proper environment and a bit of luck, then it could initiate many chemical reactions that could eventually lead to the forming of some organisms. It might seem a complete fantasy for us now, but maybe we are just too carbon-centric in our judgment.

Another thing, we consider crucial for organisms to function, is water. But once again, it doesn't have to be like that. Extra-terrestrial organisms could also use different solvents instead of water, like ammonia and other hydrocarbons.

They have similar physical characteristics to it, but the main difference between them is that they are perfect solvents for most carbon-based compounds. What’s more, many planets (such as Titan) have great hydrocarbon oceans covering up nearly the whole surface, while there is no liquid water existing there. Hydrocarbons have also a way lower freezing point than water, so if extraterrestrial life was to exist in way lower temperatures than we do, it would most probably depend on carbohydrates at some point. After all, life on earth started in the ocean. If it were to start in the oceans elsewhere, no one said it must be a water-basing one.

Another important variable, we need to consider while thinking about extraterrestrial life, is the planet itself, where it would exist on.

Most importantly, if the planet is located in the habitable zone- meaning, if it's orbiting in the distance from its star, allowing it to have liquid water on its surface, and its temperature is neither too hot nor too cold. Of course, liquid water and life could exist outside of the habitable zone, but it's just less likely. So, while searching for exoplanets with potential for supporting life, we narrow down our search just for the ones in the habitable zone.

Being in a habitable zone still doesn't grant the planet to have life on it. For life to exist, the planet must shield itself somehow from radiation coming from space, using atmosphere or strong magnetosphere. The solar wind coming from the host star would completely “sterilize” the planet's surface of any living forms, especially if its effect has been long-term. Besides that, if we think of life from an earth-centric point of view, it would need stable physical conditions, so it can evolve in peace. Without drastically changing temperature in a day, or meteors lurking around the corner, ready to wipe out all those hardly acquired life forms and organisms.

An atmosphere would be pretty useful in that scenario. It shields planets from potential meteorites and space radiation and uses the greenhouse effect to keep the temperatures stable. That creates rather stable conditions on the planet (at least much better than on a rocky, atmosphere-less one) and allows life to evolve.

So, if we are to look for a planet of best fit for extraterrestrial life, it must:

orbit not too far, nor too close from the host star- be in the magical habitable zone, which is closer for smaller stars, and further for bigger

be big enough to have strong gravitation- otherwise, all the particles creating the atmosphere would simply fly away into the space

and, finally, have the said atmosphere and then magnetosphere

Okay. Let's say there is a hypothetical planet that perfectly matches all of those conditions. Now what?

The most optimistic answer to that question would be to get ourselves a nice chair, sit down and wait approximately 3 billion years for life to form, as it was in the case of the earth. Then, wait other millions of years, so there is anything more on the planet, other than primitive cells and bacterias- something like fauna and flora. And wait, wait, wait even more, until intelligent life appears. If it ever does.

Okay, that doesn't seem so fun. So what is the other answer?

Well, we don't know if it will ever form and how long will it take for it. Especially if we are talking about extraterrestrial intelligence. It might be even possible we are completely alone in the universe, and we will forever remain like that. But to understand this process better, we need to take a look at how life on earth developed. Only then we can bring in the odds and numbers.

THE ORIGINS OF LIFE

Scientists still aren’t sure about how life on earth's origins. No wonder why, since the first organisms have appeared over 3 billion years ago! Still, some scientific theories are trying to answer that question.

The most common one states that life forms came from inorganic matter. It’s worth mentioning, that 3 billion years ago Earth’s atmosphere was composed of completely different elements - it had much more hydrogen, as well as methane and ammonia, and very little oxygen.

Such ingredients and many other inorganic substances started to spontaneously create chemical reactions with each other, which lead to creating the first amino acids, and then the other substances crucial for life (like RNA or DNA). Then, some electrical spark would engage all of those puzzles to settle down together, and voila! we have the first cells. They would then form the first organisms, and if they wanted to further evolve, they would have to stay in an environment with conducive conditions- meaning allowing all those reactions to happen. At least for a while. So, we assume the first cells started in water- presumably in the ocean or in some sort of hot springs or swamps.

But there is also another way of explaining how life got on earth. It’s called the theory of panspermia, and it says that the first forms of life haven’t evolved on earth, but have been brought there.

Panspermia is a hypothesis, stating that life forms can be transferred from one astronomical object to the other- with the use of, for example, a meteorite or an asteroid. the said meteorite would be injected with microorganisms from one planet containing life (intentionally or not) and then transfer to the other. Generally speaking, we could say that panspermia means “infecting” planets with life. Sounds cool, does it? But there is one problem. Namely, the universe is filled with radiation coming from nearby stars and other sources. Those are mostly ultraviolet and gamma rays, which would completely shatter all the DNA and RNA structures inside of a cell making it won't capable of reproducing anymore. So, if the organisms bringing life to other planets were to survive and reproduce, they would have to be extremely resistant to radiation.

But that doesn’t disprove the theory. We know that on earth there is a special kind of microorganisms, called extremophiles. Those interesting organisms are able to withstand extremely unwelcoming conditions, and even seem to favor them. There are ones living in extremely high pressure (down in Mariana Trench), in conditions of very high salt concentration, and even resistant to UV radiation! So, if panspermia was to be the main source of life on other planets, the extremophiles would probably partake in it.

So, we got life on board. Hurray! now, let’s sit down and wait approximately 3 billion years for the intelligent life forms to evolve. But can we really be sure of that?

INTELLIGENT LIFE FORMS- WHAT WOULD IT TAKE AND WHAT ARE THE ODDS?

It took humanity 600 million years to evolve to its current shape since the basic eucaryotic organisms came to life on oceans and on land. But it wasn’t just the time to do those wonders. Besides the just-right conditions the earth had for terrestrial life to evolve, it has received many evolutionary triggers, that gave it perfect opportunities to advance and grow. For example, the fact that earth has a moon made its inclination (if you want to know how it happened, go check out the “the moon” post) just right, so the seasons weren’t too extreme, yet encouraging some forms of life to grow. The moon's influence also caused tides, which made the exit of the ocean for organisms much easier. Another evolutionary trigger of great importance is the mass extinction of some species, and in our history, it's the end of the dinosaur era. Mass extinctions of species, however tragic, give place for new forms of life to evolve, as it was in the case of mammals. Who knows, maybe if the asteroid had hit in a different region of the earth, let's say part of the ocean with water deep enough to absorb the energy of impact, maybe it would be some dinosaur scientists discussing the odds of extraterrestrial life, and learning, that if the asteroid has hit the earth in slightly another place, their reptilian civilization would be gone forever.

So, it is safe to say that the position of humanity, the existence of civilizations, and the whole evolutionary process of life on earth, we owe only to a stroke of great luck and good fortune. If anything in our history would have gone differently, there is a high probability we wouldn’t stand where we are standing. So, it could be really hard for extraterrestrial life to have the same amount of fortune.

so, what are the odds that it can actually exist?

The chance, or to say better- the number of civilizations in our universe, with whom the communication might be possible is stated by the Drake equation:

Right now, we don’t know most values hiding under those mysterious letters (like how many planets can we consider habitable for life and so on), and we can barely estimate or even try to guess them. But just looking at this equation, we can see, that the value will rather be very low, and that alien civilizations aren’t waiting for us in every corner of space. Still, the universe is so great, and even if the chance is really low, alien life should still be somehow existent. So, as Enrico Fermi said,

"Where are they?"

according to Fermi Paradox, there are a few ways to explain the current situation.

1. we can’t communicate with aliens, because they do not exist:

a) and never did- as I wrote in the origins of life part, the conditions on earth and the conditions for development that the terrestrial life had received, are very rare and hard to obtain, if not completely unique. Some scientists even assume that it isn't possible for any other planet to have such favorable physical conditions (like a good place in the planetary system, the star of the right size and age, an atmosphere rich in oxygen and etc.) and this lucky evolutionary trigger configuration, so the earth is truly one in its kind. This statement is expressed in Rare Earth Hypothesis- we were always alone and forever will be. It can't be confirmed for now whether this theory is true or not, but it for sure it's a possibility.

b) because complex life is destroyed by nature further in time- some random events happening in space from time to time, like meteorites impacting planets, host-star or supernova explosions don't cause somehow beneficial for evolution mass extinctions but are destroying all forms of life, and completely wiping off all intelligent life forms before they even get the chance to develop and try to contact with others.

c) because intelligent life forms destroy themselves- as we know in the case of humanity, intelligent life forms are powered by the two motivations: wanting an easy life, and fighting for domination among the others. The first one, taking it from a long-term perspective, could lead the civilization to doom, because of things such as climate change, complete destruction of the host planet, and both biological and physical decay of the aliens, which would result in the fall of the alien civilization tas well. The other reason for this is more direct — in the fight for domination, intelligent life forms would develop so advanced weapons (like nuclear weapons or something as powerful), that both sides will end up killing each other, and coincidentally destroying the whole civilization. Therefore, alien life would never survive long enough to contact others.

2. aliens exist, but we cannot communicate with them

a) because the universe is too big, and the civilizations are too widely dispersed- the distances in the universe are enormous, and if civilization is located thousands of light-years within our reach, there is no way to confirm if it exists or not, let alone try to contact them. Another explanation for it, that alien life might have settled only a part of the universe, and we have the (mis)fortune of being in the uncharted area of it, so we also would probably be never able to reach the galactic civilizations.

b) because there are some obstacles making communication hard or impossible- for example, the attempts to communicate with other civilizations require the aliens too many resources to be successful, or there could be some physical issues (other from the distance) making it impossible, like the gravity of a planet being too strong for rockets to launch into the space, or said civilization could evolve near a black hole. Either way, they will remain hidden for us.

c) because we have passed each other- as it takes so many factors for intelligent life to come into existence, civilizations could be such a rare occurrence, that their existence is divided with millions of years. So once we developed technologically enough, to be able to communicate with them, the alien civilizations would have already vanished, and when the other civilizations will advance enough and be ready for communication, we will be already gone. In that scenario, we can say that the universe is a great cemetery of all the fallen civilizations, waiting for more to come. Pretty depressing.

d) because they haven’t yet got created- Maybe this is a pretty selfish and anthropocentric concept, but from the Drake equation we know that forming civilization is a damned long and complicated process. Maybe alien life is already existing, but it is not responding to us, as it’s still in its primal form, not able to create civilizations, like how it was with dinosaurs or early mammals. We would just have to wait for it. Millions or billions of years.

e) because we are not open for communication for long enough- our civilization exists only for around 5 thousand years, and the first radio telescope was built in 1937. The first radio signals from earth capable of getting through the atmosphere were started to be transmitted in the late ’50s. That's a blink of an eye in the time scale of the universe! And we can’t be sure, that the aliens send us signals or messages capable of traveling all of those light-years every day. So maybe they sent us a sign, but it hasn’t been yet received by us.

Another thing is that we haven’t been open for communication for a loong time. If some alien scientists or representatives were scanning the solar system for any planet capable of forming a civilization millions of years ago, the earth couldn’t anyhow suggest, that it might contain intelligent life in the future. Our solar system and planet don’t really stand out, so nobody could probably be bothered by it and notice any form of life developing. Even if they somehow got the lucky chance to visit earth somehow in the past, they couldn’t be treated seriously, and in the best case, treated as monsters or supernatural beings. And after such reception, no alien would treat earth seriously.

Aliens could also be existing somewhere in the universe, up for communication, but they still haven’t received our signals. We’ve only transmitted for a short period of time, and the distances in the universe are huge- even if they found our messages or signals and were able to decode them, it would probably take several dozens of years to get their response.

f) because we’re looking for them in a wrong way- when the SETI (search for extraterrestrial intelligence) program is looking for signals from aliens, it assumes two things: first, that the signal would be transferred by the use of radio waves (because they can be sent for the greatest range out of every other type of waves) and the second, that it would be emitted on the frequency of 1420mHz, the hydrogen line. The institute is looking for this particular frequency, as it is radiated by neutral atoms of hydrogen, the most common element in the universe. However, our perception of what frequencies might aliens use might be really wrong, especially if we consider the fact that the radio telescope in the Arecibo observatory can receive signals only in the range within 0,3 light-years from Earth.

So, maybe it's not that we cant communicate with them. we just do it the wrong way or have a too limited range of search.

g) because our technology is too primitive to communicate with them

from what we know, there is no more effective way of communication in the universe than electromagnetic radiation. However, we, once again, might be very wrong on that. Maybe the aliens have abandoned this form of communication long ago, and are using other, more effective methods (like using quantum mechanics to convey their messages). Maybe they also have sent us some messages based on the new ways of communication, but we didn’t perceive them as ways of cosmical communication, and rather labeled them as mental illnesses or, even better: revelations or possessions by the devil.

Those are just hypotheses though, not supported by any factual knowledge, and rather created to fill in the loops in our knowledge. On the other hand, the part about our undeveloped technology might be really making a point, and who knows how many messages from the aliens we have failed to notice just because of that.

2. aliens exist, but they don’t want to communicate

a) because communication is dangerous- do you remember what happened to indigenous people of both Americas when they tried to know the colonizers? A similar mechanism can work in the universe. Maybe aliens believe other civilizations to hostile, and try to stay out of sight, to avoid conflict, and therefore keep themselves safe. Many sci-fi works have introduced us to the concept of galactical imperialism, and that could cause other civilizations to try to hide their existence from others. And it wouldn’t prove to be a very hard task.

b) because aliens are too alien- maybe extraterrestrials don’t want to contact us, simply because we are too different from them. It might be rooted in xenophobia, some prejudices, or the mindset that humanity is too primitive and behind the times for the more advanced civilizations or even religious taboo. And maybe even that wouldn’t even be the reason why they don’t want to contact us. We have absolutely no clue about what life and the psychology of aliens may be like- it could be that solely the idea of contacting others might seem unreasonable to them and not in their nature. They could also try to communicate with us but in such a strange and unusual for us humans way (truly alien), that they wouldn't ever succeed.

c) because earth is intentionally avoided- a pretty grotesque, but still, valid explanation for Fermi Paradox could be that aliens are aware that there are intelligent forms of life on earth, but instead of trying to contact them, they'd rather just keep observing the planet. This theory is called the zoo hypothesis, and there might be many different reasons why aliens would decide on resigning from contact with humans: maybe aliens want to allow humanity to evolve and develop their civilization on their own, without the influence of other civilizations, or that they want to keep the balance of power in interplanetary relationships, so they prevent our civilization from joining the cosmic diplomatic arena.

As we can see, the answers on the topic of alien life proposed by the Fermi paradox are pretty depressing. After getting familiar with it, some people could just assume, that contacts with alien life are a closed case, and there is no way we could make them happen.

Still, some solutions proposed by this paradox don't make it exactly definite- like in the case of our technology not being developed enough, us searching for only a short period of time and/or doing it the wrong way. And that's what SETI is for.

SEARCH FOR EXTRATERRESTRIAL INTELLIGENCE

the SETI program (search for extraterrestrial intelligence) was launched in 1959 and ever since it is actively trying to find any signs or hints of what we consider extraterrestrial activity, especially as radio signals. And it had some successes.

On August 15 of 1977, the radio telescope in Ohio has registered a very peculiar signal, with really weird intensity, coming somewhere from the Sagittarius constellation. The astronomer registering it was so impressed with how unusual the signal was, he even wrote a note saying “Wow!” next to it. This caused the signal to be called as Wow! signal, and we still have no clue, what was the origin of it. Many people claim it could have been of extraterrestrial origin, and astronomers are still waiting for it to reoccur.

But extraterrestrial life could also be way closer to us than the Sagittarius constellation. Many sci-fi works believed, that if aliens were to be real, they would probably come from Mars. From what we know about this planet, for now, it has no liquid water whatsoever, and it's lifeless right now, but there is also evidence that it contained liquid water in past. Some scientists also believe that the first cells and organisms could be transferred from mars to earth in the mechanism of panspermia! But if we would be to think about what planet could contain life in contemporary times, we must go a little further from the earth- to Jupiter and Saturn. And more precisely, to their moons- Europa from Jupiter, and from Saturn’s moons: Titan and Enceladus. Both Enceladus and Europa seem crude and inhabitable at first, as their surface is covered with a thick layer of ice. However, studies from 2011 have revealed, that Europa might contain lakes of liquid water underneath its thick layer of ice, by some labeled even as oceans! Titan, on the other hand, is consisted of hydrocarbon oceans and has a dense atmosphere composed of nitrogen and methane. With no presence of liquid water and very low surface temperature (-170C), it seems completely inaccessible for life as we know it, but if we were to think about life using a hydrocarbon as solvents, Titan seems to be the best candidate for it out of all planets we know.

Besides searching for it and checking if it communicates with us, scientists have also made effort to reach out to aliens directly. Sending some probes to visit the furthest regions of our galaxy would be impossible because of time and limited resources, but we can send messages in the form of electromagnetic signals instead. They are way cheaper to broadcast and also have a much greater range, so if only given the needed time, we could reach even civilizations a few light-years away from our planet. Apart from just listening, SETI also emits signals for the extraterrestrials, as in the case of the famous Arecibo message, emitted in 1974 into the universe. It was projected by Frank Drake (yeah, the same one as the guy that created the Drake equation) and contains the information about our numeric system, atomic numbers of some most common chemical elements, like hydrogen, carbon, nitrogen, and oxygen, the formulas for some chemical compounds crucial for life, like DNA, a graphic representation of the solar system and an average human being, as well as the description of Arecibo Observatory, meaning how and where to look for it.

It was emitted as a radio signal, but it can be also projected graphically, like in the image below (on the left is the graphical demonstration of the signal, and on the right- what does it mean).

A similar signal was also emitted in the direction of the Syrius star in 2007. The way there back and forth takes around 17 years, so in 2024 we can hope for signs of response.

Additionally, each of the Voyager probes got special phonograph records attached to them, before they were sent on their missions. Those discs are called the Voyager Golden Records and contain much general information about humanity-recorded audio greetings in 55 languages (both modern and ancient), a 90-min compilation of music from all around the globe, 115 images describing earth, our solar system, and the life of humans, and other sounds, like nature, footsteps, and laughter.

Right now, both probes have finished their missions and are roaming the space without any strict destination. Currently, Voyager 1 is heading towards the star Gliese 445, and it will reach it in about 40 thousand years. The chances, that they will be found by anyone within our lifetime are low, but we haven't known that the solar system is empty, before the start of their mission. And it's great to leave some sort of legacy after us, isn't it?

The Voyager probes have left earth a long time ago though, and they might not be sufficient for SETI purposes. That's why the famous James Webb Space Telescope have launched recently! It's ready to begin its mission, and it will investigate many things related to outer space- from finding signals shortly after its creation, observing galaxies over time and the life cycle of the stars, to even finding exoplanets and looking for extraterrestrial life! This is a great leap forward in the history of astronomy, and we might be getting seriously close to developing our technology enough, to contact the aliens.

But is it really something we should be looking forward to?

"If aliens ever visit us, I think the outcome would be much as when Christopher Columbus first landed in America, which didn’t turn out very well for the Native Americans”- Stephen Hawking

This quote is really making a great point, one people tend to often forget about.

The space might be a much more dangerous place than we perceive it to be. It might be the case, that different civilizations try to fight down the others, so some extraterrestrial nations adopted this strategy, called also the theory of the dark forest (adapted from the science fiction novel The Dark Forest, by Liu Cixin). It states, that:

All forms of life desire to stay alive.

There is no way to know if other lifeforms can or intend to destroy you if given a chance.

Laying low is impossible in the long term perspective, therefore, lacking assurances, the safest option for any species is to annihilate other life forms before they have a chance to do the same.

So am I saying we should stop the search? Definitely not! Attempting to communicate with extraterrestrials, if they do exist, could be extremely dangerous for us. So, if we are given any proof of alien life actually existing, we need to cool down the excitement and pragmatically figure out whether it’s wise — or safe — to contact them, and how to handle such attempts in an organized manner.

Besides, if we were to completely cut ties with everything related to SETI and tried to keep a low-profile approach to anything relating to space, it might be too late. We have emitted radio signals and electromagnetic noise since the early '80s, so if someone really wanted to find us, they probably would have heard them anyway (not to mention the messages we sent intentionally). The same thing goes with our space probes, cosmic telescopes, and space stations floating around space- we left the footprint. And since it has already been done, we can't do anything to reverse it- just have to be wise and careful about it. And it's also better to get to know the risk or danger than to try to pretend it's not out there.

Besides, regardless of the purpose, space missions and studies always lead to science development, they breed innovation and bring new technologies to life, ones we could possibly use later in daily life or to solve other existing problems. Apart from that, the search for extraterrestrial life can also give us many answers about us as such. What is humanity's place in the universe? How has it all started? Are we really that special? The answer is for sure somewhere. We just have to uncover it.

So is it worth it? I'll leave the judgment up to you, and many other people much more competent in that subject than me. One thing I am certain of is, that, regardless of the outcome for our SETI efforts (whether extraterrestrial life exists or not), the answer will change our perception of the world forever. As a paraphrase, of the quote used in the beginning said, both possibilities are equally terrifying.

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BIBLIOGRAPHY:

Book “the science of Rick and Morty- The Science of Rick and Morty: What Earth’s Stupidest Show Can Teach Us About Quantum Physics, Biological Hacking and Everything Else in Our Universe (An Unofficial Guide)” written by Matt Brady, first published in 2019, I read it in translation (published in Cracow, 2019)

https://en.wikipedia.org/wiki/Carbon_chauvinism

https://www.britannica.com/science/extraterrestrial-life

https://exoplanets.nasa.gov/news/1675/life-in-the-universe-what-are-the-odds/

https://en.wikipedia.org/wiki/Rare_Earth_hypothesis

https://www.discovermagazine.com/the-sciences/huge-lakes-of-water-may-exist-under-europas-ice

https://en.wikipedia.org/wiki/Life_on_Titan

https://www.nbcnews.com/mach/science/silicon-based-life-may-be-more-just-science-fiction-n748266

https://en.wikipedia.org/wiki/Hypothetical_types_of_biochemistry

https://exoplanets.nasa.gov/search-for-life/habitable-zone/

https://en.wikipedia.org/wiki/Zoo_hypothesis#Assumptions

https://voyager.jpl.nasa.gov/golden-record/whats-on-the-record/

https://webbtelescope.org/webb-science

https://exoplanets.nasa.gov/search-for-life/can-we-find-life/#otp_will_we_know_life_when_we_see_it?

https://waitbutwhy.com/2014/05/fermi-paradox.html

https://en.wikipedia.org/wiki/Fermi_paradox

https://bigthink.com/surprising-science/the-dark-forest-theory-a-terrifying-explanation-of-why-we-havent-heard-from-aliens-yet/

https://www.washingtonpost.com/outlook/ufo-report-aliens-seti/2021/06/09/1402f6a8-c899-11eb-81b1-34796c7393af_story.html

https://en.wikipedia.org/wiki/Arecibo_message

POLISH ONLY SOURCES

https://scroll.morele.net/technologia/czym-jest-projekt-seti/

https://pl.wikipedia.org/wiki/Paradoks_Fermiego (the article is a bit different in polish, and I used both language versions)

https://www.youtube.com/watch?v=h6WALHqaS0c

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IMAGE SOURCES:

silicon-based life concept-art: https://www.nbcnews.com/mach/science/silicon-based-life-may-be-more-just-science-fiction-n748266

habitable zone graphic: https://eos.org/articles/aging-stars-make-new-habitable-zones

the drake equation infographic:

https://astronomy.com/magazine/ask-astro/2014/11/counting-aliens

Arecibo message graphic and explanation:

https://www.indiatoday.in/education-today/gk-current-affairs/story/arecibo-message-explained-google-doodle-1389706-2018-11-16

cover of the golden record:

By NASA/JPL - The Sounds of Earth Record Cover, Public Domain, https://commons.wikimedia.org/w/index.php?curid=137443

ending illustration:

https://www.eastmojo.com/science-tech/2021/09/09/watch-do-aliens-exist-heres-what-a-nasa-expert-has-to-say/

#astro community #astronomy #personal project #sci fi #the universe #education #outer space #popular science #extraterrestrials #extraterrestial intelligence #aliens #fermi paradox #astrobiology #extraterrestial life #SETI

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concentrated-dark-matter · 3 years

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EXOPLANETS

The times, when people were sure Earth is the undeniable center of the universe, are long gone. After the success of many space missions, such as the moon landing, or sending voyager probes to thoroughly examine the ends of the solar system (even those mysterious, earlier perceived as unavailable gas giants- we'll look into them on another occasion), we found no other forms of life, and no potential places to ready to be colonized by humans. So we began to ask ourselves questions. Is Earth, and our Solar System really one in the million? Or are there other worlds out there too? If so, are there any forms of life there? Similar to what we know, or maybe they will come as a complete surprise to us? And maybe, there are other intelligent forms of life there, and in the end, we are not alone in the universe?

Those questions lead us to discover, that, we, in fact, aren’t that special. There are other stars, planetary systems even, and they also contain planets- sometimes similar to the ones we can find in our system, and sometimes even crazier than we could expect. Those planets, meaning planets outside of our solar system are called Exoplanets and, in this post, we'll dive into their subject.

FINDING EXOPLANETS

As you probably think, most exoplanets are reaaally far away from us, so it is impossible for us to spot them with just a use of a telescope or to photograph them using a space probe. It would probably take a billion years just to travel and come back to the further ones, without even thinking of studying them in more detail! However, scientists have found their own methods of finding exoplanets, without making unnecessary long trips to them. So, let me introduce you to the 4 main methods of finding exoplanets.

a) direct imagining

Sometimes astronomers are just lucky- if the planet is orbiting around the star at just the right distance, it can be possible to detect it just by observation. It is not so easy, though.

Exoplanets are really far away, and they are millions of times dimmer than the stars they orbit around. You cannot spot them with the naked eye or photograph them with an average telescope because the light of their main star will completely cover up and overlap the light reflected by the exoplanet.

You can compare it to a situation when you try to look at something on your phone during a bright day, or just look in the distance in the direction of the sun- you can't see anything, because the sun is blinding you and covering up everything you would need to see. So what to do in such a situation? Put on sunglasses, or change the angle you're looking at your phone and maybe even position to the sun. In both cases, you try to block the sun’s shine.

Astronomers use the same method- if they want to spot an exoplanet, first, they get rid of their star's light, and only then, they can check, if anything is orbiting around it.

One of the ways to do so is called coronography. It uses a device inside a telescope to block light from a star before it reaches the telescope's detector. Coronagraphs are built inside the telescopes as an add-on and are now used to directly image exoplanets from observatories on earth. Still, direct imagining is not exactly an effective way of discovering exoplanets, since you have to be very lucky to make use of it- so, in discovering exoplanets, we rely mostly on transit and change of radial velocity methods.

b) transit

Most of you know this usual, clichéd horror trope – on the wall, set in the complete darkness, suddenly appears a shadow, passes, and shortly after, disappears. Is it a monster, a phantom, or maybe a murderer? We don’t know, but we for sure are not alone anymore.

The same thing we use in the discovery of exoplanets- it's called the transit method. We monitor the slight changes in the luminosity ( brightness) of the star, and if it repeatedly decreases, and forms some sort of a cycle, we can assume that it is the planet, which causes the changes. The bigger the change of luminosity is, the greater the planet probably is- since it covers a greater area of the star.

The scale of changes is too big to be measured by a human eye though. We use other instruments for this purpose, for example, The Kepler Space Telescope. By use of such advanced gear, we can also learn way more about the passing by planet, such as if it contains an atmosphere, and if so, what is it made of.

This method is really effective and helped us discover most exoplanets. However, it is not perfect- sometimes more planets are orbiting around the star, and their cycle is too complicated to distinguish each of them, or they orbit under an adverse angle, so they remain unseen for the instruments. What's more, sometimes the changes in the star’s brightness are caused by a planet passing by and can give us false results.

Fortunately, there are other methods, that help us check the existence of exoplanets and uncover the ones we couldn’t previously find.

c) change of radial velocity

It is rather obvious for us to know, that the star acts with a gravitational force on the planet. But some people tend to forget that the planet isn’t passive and acts on the star with its own gravity as well. Of course, the force is rather minimal, since gravitational force depends on the mass of the object, and the star is rather an obvious winner in that scenario (that's why planets orbit around stars and it is not the other way around), but we can't deny the role of the planet here. The planet pulls the star a little bit into its direction as it passes, and its gravitational impact causes the star to wobble.

If you look closely at this animation, you can actually see the star going a little up and down as the planet passes.

Small planet- small wobbles. Big planet- big wobbles. A system of planets acting on a star- really complicated wobbles!

However, as the star is wobbling, and then changing its position from the earth, the light the star emits is changing its qualities. Do you know the doppler effect? Well, it is what happens to the light emitted by the star.

For ones of you who don’t know: the doppler effect is a situation, when the object emitting some sort of waves (it can be sound, radio waves, heat, and light), is moving. In that case, the waves change their length, depending on the movement of their source. You probably stumbled across a situation, where a passing car’s horn sound is higher, when it is moving in your direction (the waves get shorter, and the frequency increases), and lower, when it is driving away from you (the waves are getting longer, and the frequency decreases).

When the star is moving away from the earth, the waves get stretched out, and as a result- longer. The color of the light of the greatest length is red, so we say a redshift happens. The same thing happens when it is moving towards us- the waves get squeezed together, making them shorter, and what is the color of the shortest light waves? Violet! So, they shift to violet.

Scientists calculate the scale of the shift, and therefore, we know in what direction the star (or literally any other object, since this effect can be adapted to many situations) is moving. Those shifts also give us the idea, what the mass and density of the planet can be (more dense and greater planets have a greater impact on the star, and the smaller and less dense have less impact on the star), making the change of a radial velocity a really effective and precise method.

It is rarely used to detect exoplanets though, as it doesn’t give us any information about the planet itself- it’s rather used to verify and check exoplanet discoveries, or to give astronomers a better understanding of how does the foreign planetary system function.

d) gravitational microlensing

The last major method of discovering exoplanets is microlensing.

Thanks to Albert Einstein, we know that very massive objects bend the fabric of time and space. Can’t imagine it? Think of placing a heavy ball on a trampoline or drum membrane. You can see, that underneath the fabric underneath it will become dent and curved, and the bigger the ball, the bigger the depression.

When light reaches a very massive object, it becomes deflected and warped- sometimes even, gravity can bend and focus light like a lens in a magnifying glass or pair of glasses.

So, gravitational microlensing happens when a star or planet's gravity focuses the light of another, more distant star, in a way that makes it temporarily seem brighter. This effect is really useful when it comes to calculating the mass of the objects taking part in the phenomenon, and then, the mass of the detected exoplanet.

The whole microlensing phenomenon is pretty hard to detect as such, but it becomes more and more relevant with the development of automatic telescopes. Still, it is used mostly in combination with other methods of discovering the exoplanets and rarely used alone.

Even though we mostly use the big three (transit, change of radial velocity, and microlensing) to discover planets very far away, we mostly don’t know what the planets look like and what is really happening on their surface. Thanks to really advanced technology though, we can sometimes define the type of the planet, basing just on raw data, such as surface temperature, mass, density, and radius of the planet, and sometimes even data about its atmosphere. Of course, we haven’t explored the whole universe yet (and I highly doubt we’ll ever do) and there always could be something surprising us, but most of the exoplanets are similar to the ones found in our solar systems. To make it easier, astronomers have divided them into a few categories, basing on their planetary types.

EXOPLANET TYPES

GAS GIANTS- Jupiter like

Mostly composed of gases, like helium and/or hydrogen- they don’t have solid ground and are just a giant ball of gases swirling above a solid, metallic core.

In space, there can be found planets even more massive than Jupiter- those are called super-Jupiters and can even reach the mass of a small star! They usually orbit very close around their star, making the temperatures on their surface really hellish.

GAS GIANTS- Neptune like

Neptune-like exoplanets are similar in size to Neptune or Uranus from our system-they usually are smaller gas giants, with hydrogen and helium-dominated atmospheres.

Terrestrial

terrestrial planets are made out of solid, rocky surfaces- in our system, that would be Earth, Mars, Venus, or Mercury. To be called a terrestrial planet, an exoplanet has to be around the size of Earth-

Exoplanets twice the size of Earth and larger can be rocky as well, but then, they are called super-Earths.

· Super-earth

For all of the terrestrials feeling offended, calm down, the super-earths aren’t better than our own planet in any case! They don't necessarily have to be similar to our home planet too- it is just a class of planets unlike any in our solar system.

They are more massive than Earth but lighter than ice giants like Neptune and Uranus. There is nothing said about the materials a super-earth has to be made from to gain its label- a super-earth can be made of gas, rock, or a combination of both. They are between twice the size of Earth and up to 10 times its mass.

· Ocean planets

And for the last type of exoplanets, let's take a look at planets of more sci-fi nature: ocean planets! This name probably rings a bell, since Kamino from the second episode of Star Wars: Episode II – Attack of the Clones, and Thalassa from the sci-fi novel The Songs of Distant Earth.

An ocean planet is a terrestrial planet, which has a large amount of its surface covered in some sort of liquid- it can be water (Earth), lava (Io), or carbohydrates (Titan).

It's hard to confirm though if exoplanets are really consisting of oceans. Mostly- because we don't have sufficient tools to check it and the distances don't allow us to analyze them thoroughly. Still, there are methods of studying an exoplanet's atmosphere, and it can give us the idea if the planet can contain some sort of liquid on its surface, or not.

But why to trouble, spend time on thinking of methods of finding exoplanets, analyzing them, if most of them are thousands of light-years away from us and we won't ever be able to visit them, you could ask.

Partly, you are correct. Some exoplanets lie dozens, or even hundreds of light-years away from our reach, so they probably won’t serve us as a weekend trip destination, or ever be studied in more detail. Not to mention we’re really far away from reaching the speed of light, and even if we were to do so, the spaceship would still need some kind of veeery effective fuel to keep it up.

But the purpose of this whole exoplanet finding program, which consumed a lot of time, money, and effort of various international space agencies, is rather different. It's to find undeniable and irrefutable signs of life. Strong and unquestionable evidence. And where to search for it? In exoplanets, of course.

But what the search for life is going to give us anyway, you could ask further?

Well, who wouldn’t like to hear about some crazy and bizarre organisms living on a planet made entirely from gas, or in some ice desert? Besides filling our curiosity, learning about other forms of life can give us a better idea of how our, terrestrial and carbon-based life, works. It can also give us an answer to I think one of the biggest questions ever- are we special? Are the forms of life we know common, or we're completely unique? The search for exoplanets can also give us a better understanding of the earth as such, and help develop technology for other uses. As I wrote in the post before, studying the moon lead us to huge discoveries in Earth’s geology, and also, the development of radio astronomy lead to a finding of a new, non-invasive way to detect tumors (source)

Still, discovering exoplanets is great a way to uncover the universe’s secrets and feed our curiosity, which is a force that always drove humanity forward to great discoveries.

SOURCES:

Book “the science of Rick and Morty- The Science of Rick and Morty: What Earth's Stupidest Show Can Teach Us About Quantum Physics, Biological Hacking and Everything Else in Our Universe (An Unofficial Guide)” written by Matt Brady, first published in 2019, I used the polish language version, published in Cracow, 2019

general source

exoplanets types (all four) + oceanic

methods of discovery, source 1 2 and 3

image sources

change of radial velocity GIF

Neptune-like planet (view from space)

Jupiter-like planet (view from space)

#astro community #astronomy #planets #outer space #science #the universe #exoplanet #sci fi #planetology #personal project #popular science #wow planets

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concentrated-dark-matter · 3 years

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THE MOON

moon. our loyal companion, and the only natural satellite of our planet.

We get to know this mysterious grey sphere while being little kids and since then, we often wonder what exactly it is and how did it happen it's up there, in the sky, getting lesser and lesser, as if it was eaten by something, but eventually returning, only for the cycle to repeat.

We then create the boldest assumptions- like, it is made out of cheese and some giant person slowly eats it and then replaces their snack back on the sky.

The same questions troubled our ancestors- in the past, the moon was assigned the divine role- in Germanic and Anglo-Saxon calendar, there is even a day dedicated to it! (Yes, it's Monday, which was the day devoted to worshipping the lunar gods and goddesses.) Moon's cycle was used to measure time, it gave light in the nighttime, during the full moon people and animals were claimed to become unhinged, or people believed it made lycanthropes transform. In Slavic folklore, water drawn in the moonlight was having paranormal abilities and could be used for spells and sorcery.

But this divine aspect of the moon was vague and people still thrived to learn more about it- this curiosity, in learning the nature of the moon led to various technological achievements- like Galileo’s first in history observation of sky made with the use of a telescope, a better understanding of geological processes happening in Earth’s inside, by investigation of volcanic processes that happened on the Moon, not to mention the development of modern and space travel technology because of the space race during the cold war.

But hey, let's start from the beginning. how did it even become our satellite?

MOONS ORIGIN

Well, the Moon’s genesis isn’t exactly clear for astronomy right now. There are few hypotheses touching that subject, but all of them have arguments that undermine them.

Currently, the most accurate theory explaining the beginnings of the Moon is called The Great Impact theory- according to it, about 0.1 billion years after the Solar System began to form, a planet with a mass similar to Mars called Theia appeared on Earth’s orbit. Initially, the planets didn't collide with each other, but after a while, the balance between the two planets was lost and it lead to an impact. As a result of the collision, a disc of debris was ejected around the Earth and kept around the globe as a ring, kept around the planet by the force gravitation. After a while, the shards would coalesce, and then form the foretype of the moon we know today.

By Citronade - Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=72720188

This theory was approved by most astronomers as a hypothesis of the moon’s origin because it also explains the inclination of the axis, the Earth rotates (which causes the seasons) as the reason for the collision. Still, some astronomers question it, since isotopes of elements creating the moon’s surface are different from the isotopes of Earth’s Stones and rocks, and the theory does not explain how these differences arose.

The other theories say the moon could chip off from the Earth at the very begging of its life when it was nothing but an insanely hot magma ocean. The particle of earth, meaning the future moon, could chip off somewhere around the pacific ocean, because of the very high centrifugal force young Earth was supposed to have. However, we don't know if Earth's centrifugal force could be so strong for that thing ever could happen.

Another theory of the moon’s genesis states, that moon could just somehow appear on earth's orbit, and the planet’s gravitational force captured the stray and pulled it down on our orbit- it isn't explained though, how such a thing could happen- either moon would fly to far away from the planet, and therefore escape its gravitational field, or it would fly too closely, leading to a collision. And the chances, that it flew in the perfect distance on the perfect trajectory, without colliding with our planet in the slightest bit are low. Very low.

Besides, the rocks creating both globes have nearly the same isotopic composition, so they have to be somehow "related", and not just adoptive siblings.

So, taking all of those aspects into account, the great impact theory is the dominating theory in astronomy as a way of explaining the origins of the moon. As it is not perfect, it also has few variations- such as there were no theia, and just two similar planets collided into each other, creating both earth and moon.

but its beginnings are just one aspect of our mysterious companion. there is also one very important aspect of it- which has filled people for years in wonder and amazement. its motion and phases.

MOON IN MOTION

ever wondered why you can only see one side of the moon? well, The Moon is tidally locked with Earth, which means that it spins on its axis exactly once each time it orbits our planet. Because of this, people on Earth only ever see one side of the Moon, which is called motion synchronous rotation by astronomers.

you can understand its motion better on the film below:

Like Earth, the Moon has a day side and a night side, which change as the Moon rotates. The Sun always illuminates half of the Moon while the other half remains dark, but how much we are able to see of that illuminated half changes as the Moon travels through its orbit. This is what created phases, shown on the image below.

source

moon's special position as a satellite resulted in one interesting event- the eclipses. both solar and lunar eclipses were assigned a special meaning in history, because of their wonderful visual effects.

lunar eclipses occur at the full moon phase. When Earth is positioned precisely between the Moon and Sun, Earth’s shadow falls upon the surface of the Moon, sometimes making it even reddish. the moon’s bloody color during that state was something very important to folklore, and all allegories to quarrels, battles, and bloodshed between the gods of the sky were related to it.

Another form of eclipses involving the moon, Solar eclipses happen only at the new moon phase when the Moon is between Earth and the Sun. During a solar eclipse, the Moon casts a shadow on Earth, and blocks or partially blocks our view of the Sun.

Solar eclipses occurred even rarely than the lunar, so their rare occurrence made an even greater impact on folklore and mythologies. In Mayan culture (by the way, Mayans were reaally advanced in astronomy for their time- they could predict the alignment of the stars for a few years before and created their famous Mayan calendar for thousands of years ahead.) during the solar eclipse, the god of destruction Kuluklan was to devour the world and then remake it.

source

contrary to popular belief, solar eclipses happen as often as lunar- but they are mostly partial and can be seen from only a specific place on the earth. Besides, the moon’s orbit is elliptical and tilted, so sometimes its shadow can be too high above the earth or too low for the eclipse to happen.

Alright! enough about the moon’s motion and origin. let's talk about the silver satellite itself.

CONDITIONS ON MOON AND THE MOON ITSELF

since conditions on the moon and its terrain are very different from what we know on earth, there is a special branch of science dedicated to it- its selenography or selenology.

Wait, why dedicate a special branch of science to a small globe, without any atmosphere, tectonic plates, or first of all, without any form of life, which makes it impossible for any form of soil, biosphere, or erosion there to happen, you could say.

Yeah, you could think that Moon is just a dead place, filled with rocks and dust (because, partially, it is), but in my opinion, it’s worth giving it a moment of your attention.

But first things first.

what are the conditions on the moon??

Because of the fact, there is no water or atmosphere on the moon ( the gravitational force there is too low to keep an atmosphere around the planet, and due to this, any water that would appear on the silver globe would evaporate in the blink of the eye), the amplitude of temperatures is very high: from +110C in the middle on the day to -180C in the middle of the night. Because of the lack of atmosphere, there is no sound or wind on the moon, so the legendary footprint of Buzz Aldrin remained in the same state after all these years. Another important difference between Earth and Moon is the duration of days (one moon day equals two earth weeks! Everything because of the synchronous rotation, so half the cycle for a day, and a half for a night) and gravity, which is 6 times weaker on the moon than on Earth- meaning, if you were to jump on the moon, you could jump 6 times higher.

As I said before, the moon has no protection from the cosmic ray and very high albedo (the ability to reflect light, measured in percents) because of the silver and white color of the surface- so the American flag put on the moon during the moon landing has now completely turned white.

The lack of atmosphere has also a great impact on the terrain of our satellite- in contrast with Earth, the moon has no atmosphere to shield it from meteorites, so it is all bruised with all sorts of craters and cavities, making them the most popular formation on the globe. They reach a really impressive expanse -because of no atmosphere, even a small meteorite, weighing about 5kg, could make a hole in the moon with a diameter of about 9 meters. nearly a half-million of the craters found on the moon has a diameter of over one kilometer.

The greatest crater on the moon, South Pole Aitken Basin, located on its south pole, is the biggest crater of our solar system, with a diameter of over 2200 kilometers. Another impressive crater worth mentioning is Mare Imbrium (Sea of rains from Latin), with a diameter of around 1120 km. You can see it on the photo below as a big, dark spot visible on the northeast of the hemisphere.

Apart from craters, the moon has also seas (mare), lakes (lacus), and bays (sinus)- but don’t feel confused, there is no water or liquids there! they’re all names for formations made from congealed magma, and they can be seen as the darker spots on the moon. interestingly, they exist nearly only on the visible side of the moon.

There are also mountains and mountain ranges on the moon- they’re covered with moon dust, called regolith (its a rare, grey dust, made from temperature erosion (congelifraction) of moon’s rocks and materials smashed into moon's surface by many meteorites and comets. The highest moon mountain is called Mons Agnes, and we can spot its range as lighter features on the moon’s surface.

HISTORY OF MOON’S EXPLORATION

I’m pretty sure it didn’t come to you as a surprise there are different geological formations on the moon. however, it hasn't always been obvious. In the middle ages, people thought the moon is a perfectly smooth sphere, as a work of God, it cannot be marked with highlands or bruised with craters. It had changed after Galileo’s and Johannes Hevelius' (polish: Jan Heweliusz) works and observations, but still, only the cold war space race made us aware of what the markings and dots on the moon’s surface are precisely, and made us unravel a lot of other moon's mysteries.

The first probe to reach the moon’s surface was the Russian probe Luna 2, and the first American probe to land on the moon and examine it was Surveyor 1- it created the first photographic documentation of the moon from its surface.

surveyor 1 probe

After that, both sides of the conflict gathered information about the moon, tried to land on it, investigated it from its orbit, until the Moon Landing- the climax of the space race. on July 21, 1969, Neil Armstrong, the Apollo 11 mission commander, was the first man to set his foot on the moon. After that, a few other apollo missions visited the moon as well, and during them, many sets of research instruments were installed, for example, ALSEP (Apollo lunar surface experiment package) research stations- they were equipped with heat sensors, seismometers, magnetometers and many more, to investigate the moon more effectively from the earth.

source

Until today, the last person to walk on the lunar soil was Eugene Cernan, a member of the Apollo 17 mission in December 1972. Although flights to the moon have been abandoned since then, as they are now considered unprofitable, Russia has announced the sending of landers and probes from the Luna program to further study the moon in 2022, as well as they declared, they plan to start the work on the colonization of the moon by the end of 2030.

Is it possible to happen? Well, I think it’s hard to say.

many people believe that the faded flag on the moon is a sign of surrender and giving up on the moon by us, as humanity. however, I still think that the moon could be an important stop when it comes to future space missions to Mars, nearby planetoids, or literally anywhere else in the universe.

it is also considered as a place that could be potentially used for colonization, but I will get in more details of it in another post. Some companies are also considering commercial flights to the moon, but so far none have taken place and they are all in the status of planning. We’re only left to hope that we have not left Moon for good and that we will manage to find reasons to continue missions and research about it.

sources:

link link (the whole page in general, since it's solely dedicated to the moon I didn't include the subpages I used) link link link link link

book "Cosmic Chronicles: A user's guide to the Universe" by Fred Watson, 2013 (where to get it), polish title:" astrohaj- jak dotknac kosmicznego pyłu", 2021 (where to get it)

polish only sources:

link link

#night sky #full moon #moon #astronomy #science #educacion #popular science #the universe #personal project

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