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Possibilities for Alien Life

Debate and discussion of any biological questions not pertaining to a particular topic.

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Possibilities for Alien Life

Postby alextemplet » Mon Nov 16, 2009 2:51 am

I've recently decided to try my hand at writing some science fiction, and I'd like to hear opinions and suggestions for what sort of form extraterrestrial life might take. I'm especially intrigued by Robert Heinlien's colonial insect-inspired "Bugs" from Starship Troopers, and I'm also intrigued by the possibilities of non-earth like biochemistry. One idea I'm toying with is a planet where all biochemistry is exactly like earth but moved one row down on the periodic table; for example, lithium would replace hydrogen, silicon would replace carbon, etc. This would produce broadly similar chemistry to earth-like systems, although the existence of d-orbitals in the 3rd period elements might be a complication, as would the heavier molar mass of all biomolecules. Still, I think it's an interesting conceptual exercise, and one thing I don't want to do is write yet another sci-fi story where all aliens are impossibly humanoid. I'd like to stay within a stone's throw of being realistically possible, although of course anything about alien life would have to be at best hypothetical.

Another concept I want to include is the possibility of modifying humans. This could go in a lot of different directions, from simply enhancing physical abilities to producing half-machine/half-human organisms like the Borg from Star Trek. I'm especially interested in mind control, since one of my main story elements will be an oppressive dystopian government that is widely perceived to be a force of good. I'm curious as to any ways that this might be accomplished, from mass hypnosis to computer-chip implants in the brain to possibly even lacing the food supply, water supply, or maybe even an entire planetary atmosphere with chemicals that coerce submission to the established authority.

I think there's a lot of great fun to be had just thinking about all the possibilities here, so any ideas that anyone has would be most welcome!
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Postby JackBean » Mon Nov 16, 2009 4:55 am

Well, I think, that use Earth/like chemistry with shift in periodic table is not much possible, if you wished to keep Earth/universal element properties. that is, lithium is much more reactive, than hydrogen and it forms different kind of substances. Also, replacing carbon with silica is not good choice, as silica has much higher affinity for oxygen, so it's substances are more like Si-O-Si-O-Si-... (silicones) instead of Si-Si-Si-...
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Postby alextemplet » Mon Nov 16, 2009 6:23 am

Well one possible scenario that might explain a planet with heavier elements might be the nearby presence of many super-massive stars; the shorter life-spans and accelerated fusion rates in these stars could litter the surrounding space with more heavy elements than we find in our neck of the woods. Possibly areas near the center of the galaxy or around globular clusters might be good candidates for such a planet.

I realize using lithium presents something of a problem, but the lack of oxygen that would be present in such an environment makes silicon a practical alternative to carbon. It also has four valence electrons and can form similarly endless chains of itself. Sulfur would be oxygen substitute in this environment, although the presence of d-orbitals makes it much more likely than oxygen to bond with itself instead of other elements. Nevertheless, sulfur and silicon have been suggested and studied as the most likely cornerstones of any non-earth like biochemistry.

Other possibilities that have been proposed involve liquid methane as a solvent instead of water. This might allow life to exist on much colder planets where water would freeze but methane would remain liquid, although the nonpolarity of methane would completely change the nature of which biomolecules would be possible for which purposes. Still, it might be possible; NASA is considering sending probes to Titan, Saturn's largest moon, precisely because it contains seas of liquid methane, to find out if life really can exist in such an environment.
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Postby JackBean » Mon Nov 16, 2009 6:37 am

Well, does really silica form such chains in between itself? That would need more examination, the energy of bond between Si-Si and Si-S.
Also, don't forget, such a life could work here also, we have quite plenty of silica on Earth ;) So you do not need to explain this much, more like, why there is not C-based life ;)
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Postby alextemplet » Mon Nov 16, 2009 8:56 pm

The biggest problem with silicon would be its greater reactivity and hence lack of stability. One thing I found interesting while researching is that silicon dioxide (the equivalent of carbon dioxide) is solid at temperatures where CO2 is a gas. This suggests it might only be practical to have such a heavy-element biochemistry in extremely hot environments. Perhaps it might fit into the storyline as an example of a hot-temp system along with another planet that might have methane- and ammonia-based biochemistry as an example of a cold-environment system.

Another idea that intrigues me is the possibility of a biochemistry that is exactly like that on earth except with opposite chirality. If I allowed myself to completely ignore rules of probability, I could have a planet inhabited by a species completely identical to humans in every way except chirality. This would presumably make interbreeding impossible, but might be interesting as to how two such cultures would react to and interact with each other. Given that one of my biggest reasons for writing this is to voice some of my opinions critiquing today's society, I might decide to pursue such an idea as a vehicle for social commentary.

I'm also interested in the possibility of genetically engineering humans with enhanced capabilities, especially enhanced sensory perception. For example, humans that might share a snake's ability to sense infrared light or a dog's ability to hear high pitch sounds normally inaudible to humans. I'm really wondering how much of this might be possible without being externally visible; such people with enhanced cabalities could prove useful to an oppressive government if they were able to blend in with the general population as under-cover spies or assassins. In fact, I think I might have my government intentionally limit the spread of such enhanced traits by engineering them to be either recessive genes or perhaps linked to genes that cause sterility; this would allow a government to manufacture all the agents it needs via cloning while ensuring that the bulk of the population remains unenhanced and thus more vulnerable.
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Re:

Postby JackBean » Tue Nov 17, 2009 7:30 am

alextemplet wrote:The biggest problem with silicon would be its greater reactivity and hence lack of stability. One thing I found interesting while researching is that silicon dioxide (the equivalent of carbon dioxide) is solid at temperatures where CO2 is a gas. This suggests it might only be practical to have such a heavy-element biochemistry in extremely hot environments. Perhaps it might fit into the storyline as an example of a hot-temp system along with another planet that might have methane- and ammonia-based biochemistry as an example of a cold-environment system.

Yeah, that's the effect of d-orbitals and totally different structure, altrough the formula is "the same" :wink:

alextemplet wrote:Another idea that intrigues me is the possibility of a biochemistry that is exactly like that on earth except with opposite chirality. ... inhabited by a species completely identical to humans in every way except chirality. This would presumably make interbreeding impossible, but might be interesting as to how two such cultures would react to and interact with each other..

Now, this is interesting idea! :)) Althrough, as discussed in another forum (Is evolution determinant?), will there be human beings? And even if so, will they have the same society? Just look to Earth and ho many different people (societies) there is...

alextemplet wrote:I'm also interested in the possibility of genetically engineering humans with enhanced capabilities, especially enhanced sensory perception.

Well, if you had people enough clever to be able to modify human genome (and get viable people;), than this should not be a problem ;)
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Postby alextemplet » Tue Nov 17, 2009 10:01 pm

JackBean wrote:Now, this is interesting idea! :)) Althrough, as discussed in another forum (Is evolution determinant?), will there be human beings? And even if so, will they have the same society? Just look to Earth and ho many different people (societies) there is...


This is why such a plot element would have to be a complete assault on the laws of probability; realistically, we can't expect a species to be exactly identical to humans with the sole exception of chirality. Of course, as a plot device, and as a vehicle of social criticism, it raises some interesting possibilities. As far as society, I think it might be interesting to choose to make the opposite-chirality people a complete polar opposite of "normal" people; that is, a completely free society to oppose my dystopian authoritarian society. Given the external resemblance, it might be very easy for the two sides to infiltrate spies into each other's camps, making for all sorts of fun storylines. The real question is would these people be considered human, or a separate species?
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Postby MrMistery » Wed Nov 18, 2009 4:28 am

alex,

I think I should give you one piece of advice: don't go overboard. by studying the evolutionary processes that went on on earth, it is quite probable to me that aliens would look very similar to humans, if their planet was similar enough to ours. Evolution tends to come up with the same solutions to the same problems - the best example I can think of for that is the mammals of australia which are almost identical to the eutherian mammals in other parts of the world that live in similar habitats. So i think it all depends on how similar you want the physical planet to be.

About the chemistry, you might want to reconsider. Li-S-Li for example is very different from water in that it's very ionic, there's not much orbital overlap there. I also doubt Li2S molecules and others like them could form Li-molecules. I think if you closely analyze the molecular orbitals of your imagined chemistry you might see that it is very improbable. Plus, why would that ever happen? Hydrogen is the most common element in the universe, and heavier elements are rarer than lighter ones
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Postby alextemplet » Tue Nov 24, 2009 10:32 pm

That's a good point, Andrew, and I've been thinking about what characteristics of life on earth would be most likely to exist in alien life as well. Things that have evolved multiple times independently on earth (such as limbs, eyes, heads, segmentation, body cavity, etc) are probably going to be very common throughout the universe, because they have obvious utility. Other features, such as the vertebrate mechanism of using the breathing aparatus to produce sound, are rarer and other mechanisms of communication can be just as useful, such as the many sound-producing systems found in insects. My main concern is not to duplicate the impossibly fictitious aliens of star wars and other mainstream sci-fi where everything is a four-limbed biped that speaks with its mouth.
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Postby mith » Wed Nov 25, 2009 7:56 pm

FYI fusion in the sun does not produce uranium. Apparently it peters out at iron.
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