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I am designing a terraformed Venus, where the planet has been given an Earth-like atmosphere but keeps it's original rotation rate. Colonists are importing Earth life to Venus to add a biosphere to the planet. My question is whether or not Earth life could survive the long day-night cycle of Venus? Research done into the atmosphere of a terraformed Venus says that the atmospheric circulation will be enough to keep the night side of the planet close to the temperature of the day side, so temperature is not a problem. If this Earth life can't survive a 100 day long night, what is the maximum period of time it could?

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    $\begingroup$ With all due respect to Clay, we recommend holding off selecting an answer for 24 hours. We have participants all over the world, and human nature is to skip questions with accepted answers. Clay's answer may remain the best choice, but the wealth of ideas from our users is still very useful, and you're denying yourself access to those ideas by, basically, closing the question. $\endgroup$ – JBH Aug 22 '18 at 3:49
  • $\begingroup$ What if you used large space mirrors to periodically reflect sunlight to the dark side to give it a more reasonable day-night cycle? $\endgroup$ – 0something0 Aug 22 '18 at 23:16
  • $\begingroup$ @0something0 I considered that, but I would rather such a mirror not be needed. $\endgroup$ – VenusUberAlles Aug 23 '18 at 0:40
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Well many plants and animals survive in places with little to no light, I would actually suggest choosing these varieties and then shading them during the sunny period. Actually many plants may need a rest period in darkness so their leaves don't burn.

Also, most trees could survive this period, as shone by the shedding of leaves in winter for about 3 months aka 90 days. However, you would need to cool them in order for this effect to happen, so I'm not sure that would help them survive, but most likely certain species could.

Plants such as grass go long periods without light if covered, and invasive species often have year long or more light deprivation protocols to kill roots.

So the answer is depending on species, yes. Anyways, I would plant crops slightly before daylight happens so they start to sprout about the time the sun arrives, and choose crops that will be ready to harvest before or soon after the sun disappears again.

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  • $\begingroup$ The night side is 10 degrees colder than the day side, so I assume that would be enough to trigger seasonal changes. Could any other biome besides temperate survive during the night? I was going to have the equator of this terraformed Venus be a tropical rainforest. If the rotation rate was quicker, say 30 days, would it survive? $\endgroup$ – VenusUberAlles Aug 22 '18 at 2:46
  • $\begingroup$ @VenusUberAlles Actually a lot of your plants may come the thick tropical rainforests, since they evolve to live in the shadows of dense trees and foliage. Of course if you had 30 day day-night cycles, a lot of the mid hardy plants might survive, but certain annuals may find it harder to survive, since they tend to live only in warm spring summer times and then make seeds by the time a cool fall arrives. Fall crops may be great at surviving though, its hard to be certain with lack of research. $\endgroup$ – Clay Deitas Aug 22 '18 at 4:15
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    $\begingroup$ I would stick to 90 day cycles, planting fast growing crops just a few days in front of the horizon line, and populate the rest of the planet with hardy grasses, perinials, and trees. $\endgroup$ – Clay Deitas Aug 22 '18 at 4:17
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    $\begingroup$ Quick comment about deciduous trees. Low temperature is not a necessity, at least not for all species. Plenty of tropical deciduous trees shed leaves during drier periods. Deciduous trees in cooler climates are impacted much more by day length than by temperature. Leaves are shed usually to conserve water and to limit damage to parts of the tree which won't survive the cold anyways. It is a careful balance between saving enough energy/water to offset the energy/water lost in regrowing the leaves. 3 months without sun and 9 with is vastly different than 1 month with and 1 without. $\endgroup$ – ColonelPanic Aug 22 '18 at 13:11
  • $\begingroup$ @ClayDeitas So which day/night cycle do you think would be the best for an Earth-like global ecosystem? Would this problem of certain plant species needing seasons be rectified if Venus itself also had more of an axial tilt? $\endgroup$ – VenusUberAlles Aug 23 '18 at 2:02
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An ecosystem could survive forever without sunlight, it just needs an energy source. For the sea creatures living in the very deep ocean, volcanoes are the source of energy, rather than sunlight. In addition, think about the poles of the earth, where there is no sunlight in the winter. The ecosystems there are able to survive perfectly well.

Your ecosystems could take on a 100 day hibernation period during the night phase, much like the winters of the earth.

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  • $\begingroup$ But surely the biodiviersity of such an ecosystem could suffer? I am trying to see if a global ecosystem, similar to what we have on Earth, could survive extended periods of time without sunlight. $\endgroup$ – VenusUberAlles Aug 23 '18 at 0:38

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