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What would it take for humans to survive on mars, without shelters, akin to the Martian, in terms of genetic engineering? Is it even remotely viable, or would some mechanical assistance (oxygen tanks?) still be needed?

For more background, assume that Earth is going to be uninhabitable, exact cause not yet determined, but Earth is going to be a no go, so humanity has to survive on Mars, we don't have enough time to terraform it, and putting down full shelters is not feasible due to limitations in the material that can be provided. Assume, that at most, the landing space vessels can be converted to shelters, for sleeping and storm protection, but also hydro/aero-ponics, but a large scale fully enclosed habitat or a dome are not viable, and can not cover the needs of the landed population (Which will number in the thousands), and the expected colony growth

Small scale local terraforming is being performed, but limited resources means it's going to be used to allow for farming.

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    $\begingroup$ I won't go too far into it - but - probably among the chief concerns is the radiation levels, unless the habitat situation is developed underground - perhaps mining equipment would suffice to tunnel deep enough... just my $0.02 $\endgroup$ – Joe Aug 30 '19 at 13:51
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Unfortunately, any genetically-engineered human that could live on Mars is going to be very unrecognizable as a human. Mars just isn't hospitable.

Two of the major limiting factors are oxygen levels and temperatures, both side-effects of a very thin atmosphere.

On Earth, oxygen levels are about 21% of the air we breathe. On Mars, it's about .2%, a whopping hundredth of what a normal human expects. You can't just engineer a human's need for oxygen away, it's required for our large size and brain function.

Second, on the equator of Mars going well below freezing at night is the norm. According to https://www.space.com/16907-what-is-the-temperature-of-mars.html, reaching -70 degrees Celsius would be a requirement, and while shelter could be used to hide during nights, you'll need to consume energy as a lifeform to stay above freezing temps, or expend some form of power to heat the shelter to be over freezing. Either option in the long run is expensive. While there are a few animals that can handle sub-freezing temperatures, they usually hibernate or stasis until it's warm enough to be active again, and those approaches probably won't work for an every night type of situation.

So, really, get Mars' atmosphere up and running somehow and you have a chance dealing with the less serious issues like the harsh soil of Mars, but with no real terraforming it's really better to just salvage Earth.

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    $\begingroup$ You overestimated amount of oxygen on Mars. It's 0.2%, but pressure is at 1%, so on Mars there is only 0.002% of oxygen, per one breath. $\endgroup$ – Mołot Aug 30 '19 at 15:24
  • $\begingroup$ That said, there can be some compromise. Engineering, say, a suitably toughened external skin or similar layer can effectively create a built-in pressure suit, and then at least external activity would be limited to needing supplemental oxygen only as issues with ebullism would be removed. Radiation can be helped with added DNA repair and free radical scavenging capability, both of which are purely cellular-scale mechanisms. You'd still need to bring equipment, but less of it which also means less to maintain, too. $\endgroup$ – The_Sympathizer Sep 1 '19 at 1:24
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Some fairly radical modifications are gonna be needed.

  1. Pressure suits. Mars is basically a vacuum. The solar wind has stripped it of it's atmosphere. The martians either need to wear pressure suits or genetically engineer themselves to have natural pressure suits, otherwise their eyes will boil and their lungs explode, and they'll quickly lose most of their water. This is gonna be the hardest thing to engineer. There's no natural version. Unless they've already been experimenting with this or they're amazing, this is beyond them probably. Pressure suits can be brought.

  2. Energy. Mars is not a rich place filled with plants and animals, it is a barren wasteland. Humans need energy. Large, photosynthetic wings are probably the easiest way, so they can spread them out to get power. They could also have reverse biobatteries which used electrical energy to produce glucose so they could charge off power generators in their ships. Photosynthesis generates oxygen, and so should allow martian colonists to survive a while in the event of a broken down vehicle.

  3. Better chemical synthesis. Mars does not have all the things you need for life available. You'll need to insert a lot of plant and other enzymes so humans can synthesize useful vitamins and biological molecules from carbon.

  4. A vastly reduced reliance on oxygen, and more use of anaerobic respiration. There's not much accessible oxygen on mars. As such, humans will have to be made much more able to last longer. More lactic acid resistance, larger lungs, more powerful lungs, some way to dump lactic acid externally. All the little tweaks that athletes have. Probably haemoglobin that lasts longer. Since we need photosynthesis, they can get some oxygen from converting water. Maybe some form of natural rebreather to remove CO2. In the long run they'll probably try to work out some way to convert iron oxide ores to oxygen or get sulfate ions as a replacement for oxygen, but that's a difficult and long term goal (unless this is well planned out) and in the immediate future the hope will probably just be to extend as long as possible the time people can rely on oxygen tanks.

  5. Better temperature resistance. Mars swings wildly in temperatures a lot, and is generally pretty cool. But, it is a vacuum, so that doesn't matter. The big danger will be overheating because you can't sweat well (vacuum suit) so, martians will need to be designed to be much better at expelling heat. The photosynthetic wings will help, increasing your surface area so you can radiate more heat. After particularly heavy labour it may be necessary to get close to the ground to cool down.

  6. Radiation adaption. Mars has effectively no atmosphere, so it's pretty dangerous. We'll need to buff up our self repair enzymes so our DNA is much more resistant to bad radiation. They'll need to hide in the earth or in colonies when there are solar storms.

  7. Water efficiency. Water is rare on mars, so all the tweaks of earth that retain water will be needed. We can't rely on sweating as much, and pee much be made much more efficient.

  8. Bone and muscle buffs. The low gravity on mars will cause bone and muscle decay in the long run. Hormone tweaks will be needed to ensure growth of appropriate muscle and bones.

  9. Hibernation. Mars is very poor on resources. It would help a lot to design ways to shut down much of the body for vehicle rides and such to reduce energy usage.

In the long run, living on mars may be possible. A pressure suit is not an insurmountable modification. With a lot more efficiency and enough fuel reserves it should be feasible to operate at a low level on mars. In the short run, enough modifications could be made to make humans a lot more functional without backup.

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You need to address low pressure and oxygen (Himalayan sherpas have adapted to use much less air most people, but Mars would require more), radiation (animals living near Chernobyl), water supply. 3 of those can be addressed by mutation/genetic engineering. Water, I guess could too (making humans more water efficient like desert animals). There are examples of animals and even humans adapted to some (if not all) of those situations at the same time.

The main issue is timeline. Second is how much mutation, including dead ends, is acceptable.

The Martian had a shelter -- the base and his suit -- to deal with these 3 items. But, a long term/permanent base will lead to adaptation to local environment.

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    $\begingroup$ "but Mars would require more" is a huge understatement. From biological point of view, Mars atmosphere is barely better than vacuum. $\endgroup$ – Mołot Aug 30 '19 at 15:21
  • $\begingroup$ What @Mołot said. Mars atmosphere is like a vacuum where freak sandstorms are possible. $\endgroup$ – Renan Aug 31 '19 at 3:31

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