I am a new person to this but I have been looking at similar questions about silicon life.

I'm currently trying to create silicon-based lifeforms on a planet with a surface temperature of about, -36.5 degrees celsius. I was thinking maybe a reducing atmosphere primarily of nitrogen, not sure about the other parts yet for the atmosphere with maybe a little bit of ammonia.

Speaking of which I was also thinking of maybe having their solvent be ammonia as a replacement of water. Also, if this does help with understanding, the star this planet orbits is a F-type star of 1.1 solar masses.

What I need help with is both figuring out if what I have could work so far and what to add or replace.

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    $\begingroup$ Hi, welcome to Worldbuilding.SE! If you havent yet, please take the time to read our Tour page. If you can, can you please add in the links to the other questions you read and explain why these did not answer your question? Otherwise this may be marked as a duplicate question if it is too similar to previously answered questions. $\endgroup$ Apr 7, 2019 at 22:32
  • $\begingroup$ I'd suggest thinking about the basic reactions that cycle energy and elements through your biosphere: equivalents of photosynthesis, chemosynthesis, cellular respiration, nitrogen fixation on Earth. That might provide more parameters on what you need in terms of atmosphere and other conditions. $\endgroup$ Apr 7, 2019 at 22:52
  • $\begingroup$ worldbuilding.stackexchange.com/questions/39278/… This I believe was it, I will admit it did answer some, but it more focused on silicon based life on hot worlds. Plus I suppose it was kinda because I was wondering if ammonia could work with a nitrogen atmosphere. $\endgroup$ Apr 8, 2019 at 0:06
  • $\begingroup$ For cometaryorbit, thank you. I'll look into these to better flesh this world out! $\endgroup$ Apr 8, 2019 at 0:07
  • $\begingroup$ Also for future reference, it is considered rather bad practice to accept the first answer that comes along as "best". You have nothing to compare it with. Give it a few days or a week before weighing the answers and choosing one! $\endgroup$
    – elemtilas
    Apr 9, 2019 at 9:02

1 Answer 1

  • 1.1 solar masses is an anomalously low mass for an A-type main sequence star (Altair, for example, which is a relatively "late-type" A star at A7V, is 1.79 solar masses).

  • An A-type star is going to have a relatively short lifetime compared to the Sun, so your silicon life will need a high rate of evolution compared to Earth life. Our solar system appears to have had a "Late Heavy Bombardment" at ~3.9 billion years ago (~700 million years after the formation of the solar system at ~4.6 billion years ago), so the solar system might not "settle out" to real stability within the best years for habitability of a bright A-type. (On the other hand, the Late Heavy Bombardment is still controversial, and you can probably avoid this sort of issue anyway with the right starting arrangement of the system.) A larger problem might be the movement of the habitable zone (or liquid-ammonia equivalent of the habitable zone) as the star ages. A star's brightness isn't constant over its main-sequence lifetime.

  • On the other hand, 1.1 solar masses suggests a very bright/hot G or faint/cool F type star, which would have a lifespan only slightly shorter than the Sun's. This would be much easier to maintain a liquid-ammonia environment over astronomical timescales. (This issue is even more important for a planet with ammonia oceans than for Earth, since ammonia has a narrower range of temperatures where it remains liquid than water does.) The liquid range can be altered by changing atmospheric pressure.

  • A nitrogen atmosphere should be fine; both warmer Earth and much colder Titan have atmospheres where nitrogen is the primary constituent. If the temperature is in the appropriate range, ammonia would evaporate from the oceans, form clouds and fall as rain the same way water does on Earth or methane does on Titan; so there would be a certain proportion of ammonia vapor in the atmosphere.

  • The biochemistry itself is much more "undefined", since we don't have any examples except Earth to work from. Given the general "brittleness" of long-chain silicon compounds, I'd suggest using silicones rather than silanes (silicon analogues of alkanes, the basic hydrocarbons) as your basic "backbone" molecules, and incorporating conventional organic molecules into the biochemistry as well. It's hard to say much more without more information.

  • $\begingroup$ I might of meant an f type star, don't know why I said a type star. Also that's great that ammonia will most likely work, for the atmospheric pressure I went with I think .9 atmospheres. Also should I add anything else to the atmosphere, like say what they breathe out. Other than that, these are also a space faring species, and for that to be possible they would need to make fire. Do I need something to replace oxygen for that I guess? $\endgroup$ Apr 8, 2019 at 0:03
  • $\begingroup$ Perhaps maybe some hydrogen to help in creating ammonia? $\endgroup$ Apr 8, 2019 at 2:07

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