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I am thinking of writing a story about a Martian civilization. It might involve humans, but, I think it will be more interesting if there are creatures adapted to the Martian lifestyle as well. So, here is a proposed creature to live on Mars:

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A burrowing reptilian, or so it seems. Photosynthesis is a tricky one. On the one hand, less light arrives at Mars than at Earth. On the other hand, the thin atmosphere means the light doesn't get as scattered. I decided that this creature would have photosynthetic skin, because it means the creature wouldn't have to worry as much about being sunburnt. When the creature is likely to be cold-blooded, that is important. Also, this can provide oxygen for the creature to survive since Mar's atmosphere is almost entirely carbon dioxide. I mean, yes, the creature would be more adapted to an anaerobic lifestyle, and when hibernating would probably go full on anaerobic, but, when active, it probably won't be fully anaerobic.

There are light sensors on top of its head, these connect to the part of the brain responsible for circadian rhythm. When they sense light, the creature wakes up. If they don't sense much light for a few hours, the creature goes back into its burrow to sleep. If after a day or two, there still isn't much light sensed, because, say, there is a global dust storm, the creature goes into hibernation. The Martian winter also forces the creature into hibernation but for a different reason. The Martian winter, even at the equator, is way down in the negatives. At night, it gets much colder still. An active creature during the Martian winter, if it isn't tiny, is going to freeze like an ice cube. Hibernation means that the little geothermal energy there is on Mars will be enough to prevent the creature from freezing to death in the winter.

As I mentioned already, this is a burrowing creature. It also is a nesting creature. This creature lays eggs during the spring, so that its offspring have plenty of time to prepare for hibernation. Because the chance of a global dust storm during any Martian year is 1/3, those that are unlucky to hatch during a year with a global dust storm will not survive, because they aren't well prepared enough. But, most hatchling deaths do not have to do with global dust storms happening at the wrong time. More are from lack of food, deformity, and predation than from global dust storms.

As the hatchlings grow, they rely less and less on aerobic metabolism. And the hatchlings start off tiny enough that photosynthesis can easily provide oxygen to all the cells, so oxygen storage isn't a huge concern for this creature. An oxygen storage system still develops though, while it is an embryo, just in case it has to flee or defend itself and thus needs extra oxygen that photosynthesis alone can't provide at a fast enough rate.

And this brings me nicely to the eggs themselves. When an adult eats another creature(yes, they go from complete autotrophs to a combination of an autotroph and a heterotroph as they grow and photosynthesis can't provide the full metabolic demands anymore), they inevitably will eat some iron oxide dust in the process. Instead of discarding all that iron in their waste products, in females, when they ovulate, some of the iron gets used to make egg shells. And because the egg shells are iron rich, they virtually blend in to the Martian landscape, which on the one hand, makes it much harder for predators to spot them without sensing infrared, but on the other hand, makes other burrowers more likely to damage the eggs, so the females will strategically place their nesting burrows to avoid this damage from other burrowers.

What do you think of my proposed Martian creature? Of course, there would be many more, but I can't ask about all of them. Is this a plausible creature to live on Mars?

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    $\begingroup$ Rather than photosynthesis Radiotrophic may be more appropriate, while the lights going to be damn thin with less atmosphere to block it & no magnetosphere at all there'll be a lot more radiation hitting the surface. $\endgroup$ – Pelinore Nov 19 '19 at 11:35
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    $\begingroup$ Regarding photosynthesis - you may wish to read XKCD's Green Cows - If cows could photosynthesize, how much less food would they need? - it explains why photosynthesis isn't applicable to animals (basically it boils down to too little surface area to provide any tangible benefit given the energy demands of a mobile animal...). You may wish to focus on radiation protection rather than harvesting radiation for energy... $\endgroup$ – G0BLiN Nov 20 '19 at 14:41
  • $\begingroup$ @G0BLiN But, the reason photosynthesis isn't viable for earthling animals also has to do with Earth's magnetic field. On Mars, you eliminate that problem for photosynthetic animals. And I do have the hatchlings start off tiny so that they can transition from full autotroph to a mixture of autotroph and heterotroph as they grow. The tinier it hatched, the more benefit it gets from photosynthesis. Also, photosynthesis provides oxygen. It doesn't really matter whether or not it provides enough sugar, it is the oxygen that is absolutely required to both use and store in the animal's body. $\endgroup$ – Caters Nov 20 '19 at 17:56
  • $\begingroup$ @G0BLin I don't know of any other biological process that produces oxygen. Chemosynthesis, the only other energy producing biological process I know of, it doesn't produce oxygen, it consumes it and produces sulphuric acid. And that is only viable in deep, dark, and hot environments, or for micro-organisms, not for creatures who live on the surface of Mars and can be seen with the naked eye. $\endgroup$ – Caters Nov 20 '19 at 17:59
  • $\begingroup$ @Caters not all organism need oxygen in the first place (like plants) - oxygen is only necessary for organism that also have enough sugar to burn. If you animal uses photosynthesis for oxygen instead of energy, where will it get energy from (or what will it burn with the oxygen)? $\endgroup$ – Nicolai Nov 21 '19 at 14:18
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First of all - no any photosynteses:

  • even here on Earth photosynthes is not an option for any animal. It would cover merely percents of animal energy (i.e. oxigen) needs. It is effective for plants because they do not move or actively pump anything.
  • Mars has times lower solar energy on its surface compared to Earth. Plus it has those dust storms - they are not dangerous in terms of wind pressure (you will bearly feel it with your naked skin), but they close skyes form Sun for months. And even in an anbiosis sleep animal do need oxigen.

Since photosyntes is a key feature of your organism - it is not plausable.

I suggest you to "split" this organism in two living in symbiosis like ants and aphids. But instead of aphids there should be "fields" of plants wich accumalates spare oxigen in some sacks or some other way of transfering oxidiser to "ants" through feeding. "Ants" are "responsible" for spreading fields and keeping seeds undeground in winter.

UPD (due to comments):

Why do such creatures exist is completly out of scope of asked question (plausable or not?). For me it is more like artificial creature: may be humans , may be aliens do some biological experiment on Mars. So I asume no other biosphere is present and no Mars terraforming were held. Mars is as it is now.

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    $\begingroup$ The problem seems to me to be (both in the original question and this answer) that you're trying to design one tiny part of an ecosystem in isolation without any consideration of what it has evolved from, what else has evolved. I agree photosynthetic skin won't meet the energy requirements, but where have these plants and ants evolved from, why and how have they developed this synergy? If you can answer that you will probably find the answers inform you a lot about what else you will find in your Martian ecosystem. $\endgroup$ – SO failed us all... Bye... Nov 19 '19 at 11:23
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    $\begingroup$ If you do not like the answer, please, leave some comments why. It will improve both mine and yours expirience at this site. $\endgroup$ – ksbes Nov 20 '19 at 6:38
  • $\begingroup$ I didn't downvote the answer. I agree with your general comment about photosynthesis not being viable. I don't think your idea about organisms living in symbiosis harvesting some form of oxygen rich material from plants is terrible either, but why do they exist and what else exists? On Earth there isn't just one type of mammal, there are lots of quite similar mammals. Same with fish, plants etc. So if there's one creature that harvests oxygen from plants there are probably lots; what do they offer the plants in return? Do the plants compete to provide the most attractive "oxygen fruits" etc.? $\endgroup$ – SO failed us all... Bye... Nov 20 '19 at 12:36
  • $\begingroup$ This answer provides a good treatment to the photosynthesis aspect. I think it can benefit from discussing some of the other suggested aspects before suggesting alternatives (e.g. iron rich eggshells [plausible?], camouflaged eggs in strategically placed underground nests [why?], borrowing creature basing it's hibernation cycle on light sensors [does this work in a cave?] mostly anaerobic lifestyle even when active [not sure...]) $\endgroup$ – G0BLiN Nov 20 '19 at 14:54
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Maybe

You might be able to get away with this if your animal has a unique life cycle.

For example, maybe it is dormant for long periods of time, and its burrowing consists of digging itself into the ground to the point where only its armoured, photosynthetic back is exposed. It waits for days, weeks, months, whatever, generating enough energy to keep a very slow metabolism going while it uses the converted oxygen to create oxygenated egg materials for its young.

The young get laid in a depression under its belly, then the thing just continues generating energy in the form of heat and food for the young. When the young are born, they burrow into the body of the parent, killing it but getting nutrients and oxygen from its body. When they are old enough, they emerge and instinctually move to new areas, where they burrow in and repeat the process. The mobile part of life is very small, and uses up the energy they retained from Mom.

Mating might be done by having the first ones to burrow in a new area have some color or shape that identifies them. Maybe the males are smaller and not photosynthetic, and they live just long enough to impregnate the females, becoming food for them because in that hostile environment every joule counts.

If you want something more sophisticated, consider something like an anthill or a beehive, where instead of 'workers' you have photosynthetic castes which climb to the top of the hill and spread out around it. Other, more mobile castes bring them some kind of nutrient and water, and in return the photosynthetic ones produce sugars that the hive lives on, and cumulative body heat from all the animals in the hive keeps the temperature reasonable, just like anthills on Earth. Something like that.

But a normal, mobile insect or reptile? Nope. Not enough energy.

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