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I had an idea for an alien world I want to set a story on and if this question proves popular I might ask other questions regarding this world.

The world in question is an earth like moon orbiting a gas giant. The moon is earth like in the sense that it’s about the same size and gravity, oxygen nitrogen atmosphere, and plenty of water to support a vibrant biosphere, but that’s where the similarities pretty much end.

Much like Io, this moons proximity to its parent gas giant planet means that the tidal forces creates friction in the core as it orbits, fueling the moons unreal volcanic activity. While a great deal of the planet resembles the Danakil Depression, blood red soil interrupted by vibrant hot springs filled with various extremophile microbes, other areas of the planet are far more like Yellowstone National Park were there are still plenty of hot springs and geysers, but also an abundance of plant and animal life.

I was trying to figure out how the biosphere might work on this alien world one thought stuck out to me that I am having some difficulty trying to answer on my own.

What color would the plants be?

I don’t want the plants to be green because then it might be a little too earth like. And I am man enough to admit I don’t know enough about volcanic material and how plants would incorporate the various gases and minerals and how that would affect color.

So my question is: What color would plants be on an geologically active hot spring planet?

Jacob Badger
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    I imagine the fact it is a hot springs planet would have little to do with the colour of the plants and much more to do with the sun. – DKNguyen Mar 30 '21 at 02:07
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    The type of sun and atmosphere decide plant pigmentation, not geology. – rek Mar 30 '21 at 02:38
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    Plants on earth all have the same sun and the same atmosphere and there are marvelous variation in color -- both in shades of green and plants that are not green. – Mary Mar 30 '21 at 03:00
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    As has been pointed out every time a plant coloration question comes up, you can make them whatever color you want as because the dominate color of plants is due to pure chance. vote to close as a duplicate A more alien world: Flora – John Mar 30 '21 at 03:03
  • @rek even that has little to do with a plants color – John Mar 30 '21 at 03:05
  • There are four main lineages of photosynthesizing organisms on Earth: the cyanophytes (chlorophyll d, turquoise, cyan or however you call blue-green), the rhodophytes (phycoerythrin, red), the phaeophytes (yellow-brown, due to the presence of the auxiliary pigment fucoxanthin), and the chlorophytes (chlorophyll a and b, green). It just happened that land plants evolved from green ancestors... – AlexP Mar 30 '21 at 05:14
  • @John The spectrum of light reaching the surface in the greatest quantities plays a key role, and it's why green predominates on Earth. It doesn't mean there won't be other strategies, but one is going to capture the most energy if that's where the energy is. More here: https://youtu.be/L9MNC45Jr6Q?t=513 (sources in script). – rek Mar 30 '21 at 15:18
  • @rek its not why green predominates on earth, pink/purple dominated the earth until green started forming symbiotic relationships. green captures far less energy from our sun than pink. green actually missies the bulk of the spectrum, green evolved to absorb the areas that wre not already taken by other more dominant photosynthesizes. https://en.wikipedia.org/wiki/Purple_Earth_hypothesis#:~:text=The%20Purple%20Earth%20hypothesis%20is,appear%20purple%20rather%20than%20green.&text=Co%2Dexistence%20of%20purple%20and,environments%20suggests%20their%20co%2Devolution. – John Mar 30 '21 at 15:33
  • @John I think the video addresses most of that, but pre-GOE wouldn't UV and (adjacent) violet light have been more prevalent? – rek Mar 31 '21 at 01:12
  • @rek the videos arguments breakdown once you realize there are photosynthesizers that use every color pigment on earth, the idea that a photosythisizer would absorb too much light makes no sense since they can control how much photopigment they have, worse plants actually use multiple photopigments to absorb more of the spectrum making the argument even weaker. Just because someone makes a video about something does not make it true. Also the sun would have been redder due to being younger. – John Mar 31 '21 at 02:34
  • @John Plants on Earth have evolved mechanisms for coping with too much light and repairing the damage caused by absorbing too much light, so obviously too much light is an actual thing. Your local garden centre is likely organized by how much sunlight plants can tolerate. – rek Apr 07 '21 at 13:24
  • @rek that is not too much light that is too much light for what that specific plant evolved to tolerate, If a plant evolved in a low light environment is obviously will not handle over exposure well, Its no different than frost harming a tropical plant. Most damage done to plants by excessive light is through dehydration, which is a question of resource management not the light itself. The other damage is done by a fault in chlorophyll itself that other photosynthesizes do not suffer from. – John Apr 07 '21 at 13:41

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Whatever color you want them to be. Even here on earth, there are a number of pigment chemicals in leaves.

Consider whether they use photosynthesis, or whether they, like the deep-sea sulfur bacteria, live off the vulcanism. (Or, of course, both, in some combination.) You don't have to use chlorophyll for the first, but the second gives you a much freer hand since there are no multicellular life-forms that use that on earth. (Those on earth do use sulfur, which you may want to factor in.)

Also consider the chemicals that plants may produce in order to protect themselves from the heat, or the chemicals spewed from vents. These may also have colors that will in fact dominate to the human's naked eye.

Mary
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  • Not to mention that outside the Chlorophytes there are three other lineages of photosynthesizing organisms which could have been picked by Lady Luck to give rise to the land plants... – AlexP Mar 30 '21 at 05:11