Alien existence?

[Deleted]

Jun 25, 2013 20:14:49 GMT 5 creature386 said:

As most people use the "infinity" argument, what about limiting to the observable universe (diameter of 93 billion light years)?

Still far far far far far far far far far far far far far far far far far far too large for Earth to be alone. You can't even grasp how large 93,000,000,000 light years is.

[creature386]

I can't even grasp how large the distance between Proxima Centauri and our sun is.

[LeopJag]

Life on this planet maybe of extraterrestrial origin...

Does Life on Earth Come from Mars?

WeÂ’ve all heard the theory that life on Earth originated on Mars, but now there is fresh evidence to support it.

New research presented at a recent scientific conference suggests that the Red Planet was actually a much better place for life billions of years ago and therefore the very likely source of the first living cells that appeared on Earth.



The theory was presented at the Westheimer Institute for Science and Technology by Professor Steven Benner. According to generally accepted theory, life appeared on Earth 3.5 billion years ago as the planet began to cool down. The drop in temperatures allowed the formation of simple organic compounds, which then combined into polymers and eventually became the first protocells.

Evidence suggests that these first cells used RNA replication and that life forms switched to DNA replication a lot later. But according to Benner, this theory of RNA replication does not hold, as the process would have been very rare if Earth was indeed submerged in water back then.

The formation of RNA requires two essential components: borate and molybdate and if these are absent, organic molecules dissolved in water result in tar instead of RNA. But both borate and molybdate would have been scarce on Earth billions of years ago.

However, Benner says the minerals would have been abundant on Mars, something confirmed by the recent analysis of Martian meteorite. Scientists have collected and tested 120 Martian meteorites so far and most of them indicate that both catalysts needed for RNA replication were present on the Red Planet.

Another element that further supports the theory is that water is corrosive to RNA, so replication would have been a lot more likely to happen on Mars, which had significantly less water than Earth did.

According to banner, the most recent evidence adds extra weight to the theory that “we are actually all Martians” and that life on Earth actually started on the Red Planet and came here “on a rock.”

While we are still a longs distance from seeing definitive proof of the actual origins of life, the latest discoveries give hope that we will eventually find life on Mars and other worlds. What do you think of the theory? Share your thoughts in the comments below!

[Image via Telegraph]

techbeat.com/2013/09/does-life-on-earth-come-from-mars/

[Deleted]

This should extinguish the skepticism against alien life.

www.youtube.com/watch?v=17jymDn0W6U

[creature386]

To revive this thread, I finished my made up solar system:

Welcome to the beginning of my new series, where I show my made up planet system, the "Gaidos System". Before I start the series, I will say where the name Gaidos comes from. Gaidos was one of the authors of this paper:
www.jstor.org/stable/pdfplus/20048571.pdf

Now let's start (this episode is basically for giving an overview about the planets and the sun):

Episode I: planets and sun

The Gaidos System is located within the Local Group:

The Local Group is also the group, which includes the Milky Way. The Gaidos System however isn't located in the Milky Way, it is located in the Andromeda Galaxy, which is the largest galaxy in the Local Group (diameter=140000 light years):

The Gaidos System is located somewhere in the heart of that galaxy and therefore around of 2,57 million light years away from earth.
Now, let's look at the system itself. It's sun is a red dwarf star, which is called Gaidos. The planet system includes five planets. Because of the weak light of red dwarf stars, the closest planet (Gaidos prime) is the one in the habitable zone. The first two planets are rock planets, the next two are gas giants (Gaidos Alpha and Beta). The last one is again a rock planet. We will focus on Gaidos prime.
But first some information about it's sun, which is a red dwarf star:

Red dwarf stars are the most common stars, but also among the smallest (their mass amounts to 0,6 to 0,08 times that of our sun). Unlike main-sequence stars, they are not visible from the earth with naked eye. Their light is also weaker. As mentioned, habitable planets have to be quite close, because they need to be warm enough, but not too warm. For life, water is required (in the next entry I will explain why this is so important), if it is too cold, the water will freeze, if it is too hot, it will boil away.
The distance to the sun has consequences. Gaidos prime is tidally locked, due to the low distance to it's sun (Note: This does not always happen, the Mercury is not tidally locked, although some planets like HD 189733 B are). That means it has no rotation and the same side of the planet faces it's star. The problems are obvious. It exist a day side, which is quite stormy, with average wind velocities of 10-20 m/s, while the other side is eternal darkness, to show how this would look, here is Aurelia from extraterrestrial:

There are more problems a red dwarf star offers, but I will show them in the following episodes. A great advantage of red dwarf stars is their enormous life span. They can live three times as long as a normal sun and therefore life has much more time to develop.
Now some details on the system. Red dwarf stars show a great variety of mass and radius, but our star is comparable in overall dimensions to Gliese 581. Gaidos prime has a radius of roughly 6000 km and a core which is similar to that of our earth and therefore a similar density. The planet which has the second lowest distance to it's sun is Gaidos defteros, who's radius is 1000 km longer than that of Gaidos prime. It isn't habitable, as it is already outside of the habitable zone. The next planets are gas giants, the already mentioned Gaidos Alpha and Beta. Alpha is the larger one of the two, but both are larger than Jupiter. The last one is Gaidos parvus. The most far away and smallest, comparable in size to Mercury.

In the next episode, we will focus on Gaidos prime, it's atmosphere and the evolution of life. Who wants to see complex alien ecosystems has to wait (BTW, the episodes of this series are going to be shorter and with less images than the ones in the future world, as it will be harder to find images and to make up a lot, but I will try to keep them as long as possible).
This was the first episode of my new series, thanks for reading!


References:
Gaidos et al. (2007) New Worlds on the Horizon: Earth-Sized Planets Close to Other Stars In: Science 318 (5848), pp. 210-213
Scalo et al. (2007) M Stars as Targets for Terrestrial Exoplanet Searches and Biosignature Detection In: Astrobiology 7(1), pp. 85–166. doi:10.1089/ast.2006.0125
Joshi, M. (2003) Climate model studies of synchronously rotating planets. In: Astrobiology 3 (2), pp. 415–427. doi:10.1089/153110703769016488

Episode II: Gaidos prime, atmosphere, oceans and first life

In this episode, I will explain the facts about my made up planet "Gaidos prime" in detail and I will show the evolution of life. As I explained, due to the tidal forces of it's sun, it has no rotation. Therefore the same side of the planet faces it's sun. I will show the history of the planet. We will go back in time and see it's creation. At the beginning, it is a protoplanetary disk.
To get an idea of how that looks, I will show you the protoplanetary disk HH-30:

These disks are made of gas and dust. The elements on the disks are important for the future planet. There has to be enough oxygen for water. If the carbon/oxygen ratio is too high, water will be absent, as water consist of hydrogen and oxygen. Instead it is possible that the oceans (and the atmosphere) consist of hydro-carbonates. That is a further difficulty for life, as being in the habitable zone does not equal being habitable (the Venus and the Mars are too in the habitable zone). As Gaidos prime is going to be habitable planet, it of course has the right elements on it's disk. Now, it starts becoming a planet. Despite the fact that it has enough oxygen, the atmosphere basically consists of hydrocarbonates, as oxygen very quickly reacts with other elements, when the temperature is high (in the early chapters of a planet, it is quite hot). We are now in the stage where the planet already cooled down.

Nevertheless, most oxygen is in the water (due to the hot beginnings, where all reacted), which covers roughly 80% of the planets surface. Therefore, the atmosphere consist of hydrocarbonates, as often suggest for the young earth. Because of the fact that the light of a red dwarf star has a far higher wavelength than the one of our sun (red dwarf stars send infrared light), the water absorbs a lot more heat. Due to the fact that the planet is very water rich, a lot of it's heat get's distributed trough the whole planet. This increases the temperatures on the dark side. The side is still quite icy, but there is at least a bit more liquid water. Liquid water is very important for life, because liquid water has the ability of molecular recognition, like protein recognition for specific DNA sequences (like the ones for repairing). Differences in hydration in the DNA-proteins can provide a fingerprint in the DNA.
However, because most of the light is absorbed, even in shallow waters we have darkness. Furthermore, the infrared light is problematic for photosynthesis, therefore, many lifeforms are limited to black smokers. For space reasons, they are restricted to a smaller size.
Nevertheless, later within the time, there are lifeforms which master oxygenic photosynthesis. Their chlorophyll is similar to the bacteriochlorophyll of purple bacteria.

The difference is that purple bacteria have an anoxygenic photosynthesis. There are also lifeforms using anoxygenic photosynthesis on this planet, but as on earth, the oxygenic ones dominate. Like purple bacteria, they are purple. Due to the fact that some lifeforms don't need their smokers as energy source, life can have a higher diversity. However, on Gaidos prime, there is a problem with photosynthesis. As I mentioned earlier, due to the high wavelength of red dwarf star light, even in relatively shallow water, there can be complete darkness. Therefore, organisms using photosynthesis (no matter if oxygenic or anoxygenic) are limited to the surface. The organisms came to the surface trough spots where the water is not deep and where black smokers are close to the surface. On the surface, they have a lot of competition, therefore they started spreading all over the planet. But the abundance of life forms kept rising, so the competition is still high. In exchange, they can tank energy all day, as Gaidos prime has no rotation. Nevertheless, the competition is high, so they don't have a lot more space than the animals relying on black smokers. That isn't a problem, as there are no lifeforms on Gaidos prime who consist of more than one cell:

It will take some time until complex life can evolve, but due to the enormous lifespan of red dwarf stars, enough time is available.
There are organisms using the abundance of other organisms to feed on them. They use acids or poison to kill their prey, as they don't have other weapons. When there are predators, there are also scavengers. There are lifeforms living in the great uninhabited zone (the zone between surface with fun and ground with black smokers), which rely on dead lifeforms from the surface, sinking in the depth. High competition forces the lifeforms on Gaidos prime to explore more and more habitats. A few bacteria already live on land, but there isn't even complex life in the water yet.


Sources are the same as in the last episode.

Episode III: First complex life

This is the next episode of my planet series. In this time we will go for the more complex lifeforms. We now have lifeforms with multiple cells. Some of them are the equivalent of underwater plants, just that they are purple. Due to the fact that they need very shallow water (infrared light does not infiltrate deep into water), these plants start conquering the land quite quickly. They also aren't a major part in the open sea food chain, there their smaller relatives form the basis and occupy the same niche as phytoplankton. Animals like corals, which rely on algae don't exist here, because algae can only exist on the surface and near the coast. In the near of the cost, the algae like creatures form mini reefs:

There are some plant-like lifeforms though, which live on the sea floor and live from the nutrients in the soil there (although they can't be called plant like, as they're unable to perform any photosynthesis). Again, the competition is high, as not all the spots are nutrient rich and if they are, there is mostly a single large lifeform feeding on the nutrients in the ground. Few other lifeforms around it, feed on the rest of the nutrients. The large one provides shelter for other lifeforms and parts of it provide food. When it dies, lost of lifeforms which feed on others come and eat it.
If there are lifeforms feeding on other lifeforms and not on sunlight/nutrients from the ground, this results into foodchains. Foodchains of course need apex predators. The apex predator in these waters is a strange creature with a cask shaped torso. Due to that, it is not particularly fast, but that doesn't matter. Due to the explained factors, most of the sea is dark, so it has enough possibilities to hide. The predator has it's jaw at the end of it's trunk which it uses to catch it's prey. Superficially, the creature is similar to Opabinia:

But only superficially, as it lacks eyes (see below for reasons).
It's prey items are small, stream lines creatures, which are easy to swallow. The prey items themselves "prey" on the giant algae like lifeforms. Preying is the false word, as they are only able to take out bites out of the huge lifeform. Not all of them are completely streamlined, some are drop shaped. These shapes are the most useful ones for swimming. The ones who don't live near the surface lack eyes, as they don't need them. The ones near the surface however evolved eyes. This is unsurprising, as in the history of earth, eyes evolved many times independently. The ones who lack eyes evolved other sensory systems, some are able to detect electric fields, making it harder for predators to ambush them.
We now will look at the first lifeforms leaving the water. It are of course the lifeforms relying on photosynthesis and looking like purple plants. Here, all get enough sunlight, so they don't have to restrict their distribution area. Spreading over the whole planet is not easy though. Red dwarf starts are known for their flares.

Sometimes, these flares are heavy enough for delivering damage to the lifeforms on Gaidos prime. Because it's so close to it's sun, Gaidos prime has to take the whole power of the flares. The flares consist of ultraviolet light, which is harmful to all carbon based life (as we have it here). Such flares kill many or the "plants" (except for those who are rescued by something like a rock in front of them). Later, some plants evolve some kind of parasol against the flares. The chlorophyl on the "parasol" of course gets destroyed, when there's a solar flare, but the plant is able to regenerate it. Such plants are getting more and more successful and are able to spread trough the whole landscape. Later, "animals" follow them. They benefit from the "parasols", because there are already plants large enough for animals to hide below them. Some plants even live on the "dark" side of the planet. Like in the water, they feed on the nutrients in the ground. As I said before, the competition in the water is hard, as it is not easy to live from the nutrients in the ground, so they need a lot of soil. Some animals followed them. There they of course lack eyes too and basically rely on their sense of smell. Because of the global ocean, heat is transported all over the planet and the dark side is not completely covered in ice. It's quite cold there though, comparable to Antarctica in the winter:

Because of the restricted food sources, the diversity of species is very small here.
On the sun side, the variation is higher. Here the global ocean has the inverse effect BTW. The cold water format he poles prevents the subside from turning into a storm world.
Let's come back to the species diversity. Of course most species live in the forests, with the purple plants. But there are other habitats. For example there are deserts, with lower species diversity. Here, most lifeforms live in the ground (which also provides protection from the flares). There, being line shaped is advantageous. The plants live outside of the ground of course and have no parasols. They have another amazing strategy. Most of the plant is below the ground, only a part of it is used to gain energy. When there is a flare, the plants are able to retract the part used for gaining energy. They know when they have to retract, because flares last for some time and in the beginning, the UV light is not that terrible (Source: "Extraterrestrial", the NatGeo documentary). The plants will have retracted, before the radiation reaches it's peak.
There are no flying lifeforms yet.

In the next episode, we will look at how this is going to continue.

P.S. I know, the ideas are terrible, but you hope I don't get too mad with me.

Episode IV: The end

It's now time to finish another series. We will now further look at the life on my made up planet "Gaidos prime" and I will continue showing you the ecosystems. There are flying lifeforms here. In the animal world on earth, major flying clades evolved four times independently (bats, insects, birds, pterosaurs), so it's not that unlikely to happen on another planet too. The flying lifeforms here are a bit like bats, meaning they use their limbs and a wing membrane to fly. They evolved from gliders. Many of them still rather like to start flying from a tree than from the ground, because it's easier. But there some predators lurk and wait for an opportunity to attack them there. One of them catches the fliers, while they are resting on a branch and sucks their innards. This scene is somewhat comparable to crap spiders preying on bees:

The species of flying lifeforms we're observing right now live in forests. However, some of them live in mountainous regions, where they have similar gliding advantages. Furthermore, there are less predators preying on them, but this doesn't mean the mountains are completely save. Some predators lurk between the rocks. However, the flying lifeforms are always watching for danger. As I said before, the mountains region provides great gliding opportunities, and gliding/flying is an effective way to get rid of predators. After we see such a scene (the fliers flying away from an attack), some fly in a nearby tropical forest. There, we have a lot of mud and many of the inhabitants have more than four legs, to have a saver foothold. These forests are far more dangerous than the mountains, but there is a lot more food, that's why the flying creatures regularly visit them, despite the higher danger.
The danger doesn't only include more predators, it also includes numerous parasites. Some of them are even on common leaves (the purple "plants" on this planet use leaves too, because their shape is ideal for light based photosynthesis), which are eaten by one of the fliers. The parasites are somewhat comparable to nematodes:

Like many of the parasitic nematodes on earth, it becomes dangerous when swallowed. Many of the newly hatched parasites don't survive the first few days, because at first most are sensitive to stomach acid. Usually, only one or two youngs survive out of hundreds. This species is at first just a normal parasite. It creates a small hole in the intestinal wall, and then feeds on meat it can find everywhere int he body of the host. It mostly stays directly under the skin. The host is often attacked by itching. The itching becomes more frequent, as the parasite grows. Another symptom, which increases with the parasite growth is continues fatigue (because blood is a major food component, so the host animal gets less oxygen). When it's an adult, it kills it's host, by attacking some vital organs. Most hosts don't make this experience, because they often die before, since their symptoms make them more vulnerable to predators. After the death of the host, the adult parasite lays it's eggs on the leaves of a plant, so that another animal eats them.
We'll now take a look at some other habitats.
In more open habitats. There, we also have apex predators. They are fliers too, but they aren't related with the ones shown before. These ones have wing membrane on their legs too. Because they are helpless on the ground, they heavily depend on gliding help (mountains). Because they don't have so much food there and the adults are too large for the forests, they often visit the open plains and attack smaller animals, which they can easily pick up while flying (the carnivorous flirt have to take multiple prey items, because they are too small). The predators have to fly back into the mountains, after having visited the plains. Their ability to fly for a long time is useful there. In the mountains, they're saver and they have an opportunity to flee, when required. Younger specimen can live in forests too.
The last environment we'll visit are the oceans.
Like in the other environments, biodiversity increased here. Here, it is a bit different to earth. Unlike on earth, the largest organisms aren't micropredators. It are predators feeding on lifeforms, which are often almost as big as they are. They're even cannibals. Because they prefer more open waters, they have to face the problem on a planet depending on the light of a red dwarf star, that's the darkness in even moderately dark water. That's why most lifeforms here don't rely on vision, but rather on other senses. Many predators are even able to hear sonar, because that's a commonly used way of navigation here. Some animals of course create light by themselves.

The fact that they can easily in the dark, due to their bioluminescence, is not that terrible in a world, where most can't see at all. The shallow waters (where the plants get some sun), are still quite overcrowded by both, plants and animals. When looking from naked eye at the water surface, it is possible to see a purple rug of plants, with countless little organisms romping between them. Some can be seen as a plankton equivalent, but by far not as abundant as on earth, due to the more limited light zone.

That's all I have to say about my made up planet. I don't have further ideas.

carnivoraforum.com/blog/main/3838574/?cat=1671

I know, it it's not that creative.

[creature386]

Because I'm currently having a debate on carnivora on that subject, I would like to ask you a question:
You all believe in extra terrestrial live, but does this only refer to micro organisms, or would you find extra terrestrial lifeforms comparable in size to ours plausible, too?

[creature386]

Bump, excellent article:
io9.com/5784971/how-to-create-a-scientifically-plausible-alien-life-form
Some of the proposals are really weird, such as life that takes its energy from another source than electromagnetism (to which light belongs).

[Infinity Blade]

How likely do you think it is that alien life forms would evolve to look like humans? I'm not exactly the most well-versed on the topic, but this io9 article (link) lists some ways that aliens could evolve to look like us (however, I object to the "convergent evolution" argument). Is the science there sound?

[creature386]

*Moved it here because I wanted to revive my old alien thread.*

I'm happy that at least symmetry is likely to evolve independently because my SciFi story only has symmetric aliens…
Anyway, independently evolving humanoid aliens are obviously implausible because you'd need a planet that's almost exactly like Earth with almost exactly the same history which we all know is fantastically improbable. Unless you are a proponent of the ancient astronauts hypothesis and claim, like Erich von Däniken did, that aliens created us in their image and hence look like us, but I hope noone here actually believes this.

[Deleted]

Humanoid aliens, as in simply having at least a passing resemblance to the basic primate form, aren't that implausible as you'll simply need the right evolutionary pressures to evolve a bipedal upright pose, which isn't necessarily the exact same as in ours.

Now, aliens which are simply human copies with slightly different features/additional features/different colors/etc., that's another story.

[creature386]

Just finished reading this little first contact story by Eliezer Yudkowsky:
robinhanson.typepad.com/files/three-worlds-collide.pdf
The aliens are REALLY alien. Both physiology and morality-wise.
One race (called Babyeaters) consists of sentient crystalline, insectile creatures who eat their own children. The other one (called Superhappies) are basically hedonistic tentacles who communicate by having sex.

[Infinity Blade]

Like everyone else here I would be baffled if the rest of the universe was completely devoid of any life. When was the last time any of you have encountered someone who doesn't think alien life exists? I don't think I've ever.

However, when I think of plausible alien life I still typically think of microscopic, single-celled life akin to the first lifeforms of Earth. That's because I have no idea what alien animals (if they can even be called that) would be like.

[creature386]

Sept 23, 2017 23:48:29 GMT 5 Infinity Blade said:

When was the last time any of you have encountered someone who doesn't think alien life exists? I don't think I've ever.

There are some solutions to the Fermi paradox which propose something along these lines. Though technically, this solution would only entail that there are no other civilisations, not there there can't be some microbes on other planets.

[Infinity Blade]

Sept 24, 2017 1:32:49 GMT 5 creature386 said:

Sept 23, 2017 23:48:29 GMT 5 Infinity Blade said:

When was the last time any of you have encountered someone who doesn't think alien life exists? I don't think I've ever.

There are some solutions to the Fermi paradox which propose something along these lines. Though technically, this solution would only entail that there are no other civilisations, not there there can't be some microbes on other planets.

That was a legitimate question. But I was unaware of your first statement.

[An Goldish Jade]

I think that it is possible, somewhere out there in the galaxy, there is advanced lifeforms.