We couldn't adapt to the Mars atmosphere at all. Would need to be beings rather different from us. That's because it is so low in pressure that our saliva would boil, also the interior of our lungs. Over most of Mars then the boiling point of water is below its freezing point so water boils instantly as soon as it is liquid. At the floor of the Hellas basin and a few other places on Mars then water boils at a few degrees C so you can have liquid water but it is close to boiling point.
You can get water liquid at a much lower temperature if it is very salty. Also our blood wouldn't boil on Mars because it is inside our blood vessels so contained.
So - first step is to make sure you have no water in your body exposed that can boil. So no saliva, no lungs exposed to the atmosphere.
Or if you live at the bottom of the Hellas basin, to have very cold blood just above freezing - or better still, below freezing, using antifreeze of some sort to keep it liquid.
That's all very well - but the atmosphere doesn't have any oxygen in it. Or at least hardly any, below the theoretical minimum for any kind of a a metabolism. And it is pure CO2 more or less, which is highly poisonous to humans as soon as you get to a percent or two in the atmosphere (humans just go unconscious and then die in those conditions, not from lack of oxygen, but from our reaction to the CO2).
So having cold blood, just above freezing, or ideally, very salty blood below freezing, and some alternative to lungs to trap moisture, all that is a start but you'd still not be able to survive on Mars, not long enough to draw a single breath because there is no oxygen to breath, just trace amounts of it.
So you need to have some other kind of metabolism. If you are a plant you can just photosynthesize, but your metabolism is slow.
Some microbes (halobacteria) can use sunlight in a different way,. nstead of the normal photosynthetic reaction, they use the same chemical reaction we use to detect light in our retina. As a source of energy.
Making that into a fun but very science fiction idea, think some creature that is all eyes, retina like a big optical telescope, entire body covered in light sensitive pigment, spreads out thin film sheets over the surface whenever it rests to capture light for energy not to see. Could such a creature get enough energy to live on Mars?
You need to be able to tolerate perchlorates as they are abundant on Mars. Poisonous to most creatures, especially at higher temperatures, including humans, but much less toxic at lower temperatures close to freezing or below, and some microbes can use them as a source of energy. And they also work as an antifreeze. With perchlorates in your blood, it could stay liquid at very low temperatures.
So - just possibly able to eat perchlorates? Also to eat basalt - there's a microbe that can get energy from the iron in olivine through reactions with tiny amounts of oxygen. This metabolism would need about ten times as much oxygen as there is in the Mars atmosphere so not feasible right now but maybe some creature that gathers oxygen in some way and then uses it to eat iron, is that possible?
Just throwing out a few ideas, it's a major challenge.
Is a good chance of microbes on Mars I think though as all these are metabolisms that are no problem at all for microbes.
You'd also have a better chance as a water dweller - but only occasionally on the surface. Because surface layers of water if they exist are very thin, salty, or droplets a few mms probably in size. Great for microbes but too small for anything else.
From time to time then a meteorite will hit the polar caps and could make an ice covered lake that could last for a thousand years or more, so then, briefly, aquatic life forms could live in that lake. If you had oxygen it could be a chance of surviving - but problem is that the lake wouldn't on Mars. That is unless there is some mechanism that oxygenates the water which I wouldn't want to rule out.
There may be permanent water deep down, trapped and disconnected from the surface. If so you might be able to live there as an aquatic creature of some kind. But - still the problem of source of energy. There are some multi-cellular animals that can survive without oxygen, recently discovered, so not impossible. But they are tiny creatures you need a microscope to see.
(it's not this colour - this is a stain)
ScienceShot: Animals That Live Without Oxygen
Others can manage with very little oxygen. Deep below the surface of the Earth there are these tiny worm like creatures that could probably survive in similar conditions on Mars. But a bit of a stretch to suppose anything as complex as a human living like this. Meet Mephisto, the worm that rules the underworld (Discover Magazine)
There's also the possibility of taking up water vapour from the night time humidity - again that's possible if you are a plant. If you are a lichen, you may be able to survive almost anywhere on Mars, in partial shadow. Need to be tolerant of UV, as Mars has very harsh levels of UV light. So - likely to be pigmented with melanin or parietin (a UV protective pigment of lichens). And you'd probably have a very very slow metabolism, take thousands of years to grow to any size.
Also of course you have to tolerate high levels of cosmic radiation if you live anywhere on the surface or top few meters of the soil. Not a problem if you live deep underground.
Apart from that, has to be artificial habitats.
Basically Mars is not really much more habitable for humans than the Moon. It looks more Earth-ike but the similarity is rather superficial in many ways for humans at least.
For some microbes able to live in extreme cold and salt, or dry conditions with high levels of UV, and able to tolerate perchlorates, it might seem home-like enough for small populations to survive very much living on the edge. In Antarctica some microbes in similar conditions have such a slow metabolism they have lifetimes measured in thousands of years. That's for a single microbe. Also for some polar and high arctic lichens it may seem tolerable enough as a place to live, if they can cope with the high UV and take up humidity exploiting the 100% humidity at night when the atmosphere gets so cold it can dip below the freezing point for dry ice.
You can get water liquid at a much lower temperature if it is very salty. Also our blood wouldn't boil on Mars because it is inside our blood vessels so contained.
So - first step is to make sure you have no water in your body exposed that can boil. So no saliva, no lungs exposed to the atmosphere.
Or if you live at the bottom of the Hellas basin, to have very cold blood just above freezing - or better still, below freezing, using antifreeze of some sort to keep it liquid.
That's all very well - but the atmosphere doesn't have any oxygen in it. Or at least hardly any, below the theoretical minimum for any kind of a a metabolism. And it is pure CO2 more or less, which is highly poisonous to humans as soon as you get to a percent or two in the atmosphere (humans just go unconscious and then die in those conditions, not from lack of oxygen, but from our reaction to the CO2).
So having cold blood, just above freezing, or ideally, very salty blood below freezing, and some alternative to lungs to trap moisture, all that is a start but you'd still not be able to survive on Mars, not long enough to draw a single breath because there is no oxygen to breath, just trace amounts of it.
So you need to have some other kind of metabolism. If you are a plant you can just photosynthesize, but your metabolism is slow.
Some microbes (halobacteria) can use sunlight in a different way,. nstead of the normal photosynthetic reaction, they use the same chemical reaction we use to detect light in our retina. As a source of energy.
Making that into a fun but very science fiction idea, think some creature that is all eyes, retina like a big optical telescope, entire body covered in light sensitive pigment, spreads out thin film sheets over the surface whenever it rests to capture light for energy not to see. Could such a creature get enough energy to live on Mars?
You need to be able to tolerate perchlorates as they are abundant on Mars. Poisonous to most creatures, especially at higher temperatures, including humans, but much less toxic at lower temperatures close to freezing or below, and some microbes can use them as a source of energy. And they also work as an antifreeze. With perchlorates in your blood, it could stay liquid at very low temperatures.
So - just possibly able to eat perchlorates? Also to eat basalt - there's a microbe that can get energy from the iron in olivine through reactions with tiny amounts of oxygen. This metabolism would need about ten times as much oxygen as there is in the Mars atmosphere so not feasible right now but maybe some creature that gathers oxygen in some way and then uses it to eat iron, is that possible?
Just throwing out a few ideas, it's a major challenge.
Is a good chance of microbes on Mars I think though as all these are metabolisms that are no problem at all for microbes.
You'd also have a better chance as a water dweller - but only occasionally on the surface. Because surface layers of water if they exist are very thin, salty, or droplets a few mms probably in size. Great for microbes but too small for anything else.
From time to time then a meteorite will hit the polar caps and could make an ice covered lake that could last for a thousand years or more, so then, briefly, aquatic life forms could live in that lake. If you had oxygen it could be a chance of surviving - but problem is that the lake wouldn't on Mars. That is unless there is some mechanism that oxygenates the water which I wouldn't want to rule out.
There may be permanent water deep down, trapped and disconnected from the surface. If so you might be able to live there as an aquatic creature of some kind. But - still the problem of source of energy. There are some multi-cellular animals that can survive without oxygen, recently discovered, so not impossible. But they are tiny creatures you need a microscope to see.
ScienceShot: Animals That Live Without Oxygen
Others can manage with very little oxygen. Deep below the surface of the Earth there are these tiny worm like creatures that could probably survive in similar conditions on Mars. But a bit of a stretch to suppose anything as complex as a human living like this. Meet Mephisto, the worm that rules the underworld (Discover Magazine)
There's also the possibility of taking up water vapour from the night time humidity - again that's possible if you are a plant. If you are a lichen, you may be able to survive almost anywhere on Mars, in partial shadow. Need to be tolerant of UV, as Mars has very harsh levels of UV light. So - likely to be pigmented with melanin or parietin (a UV protective pigment of lichens). And you'd probably have a very very slow metabolism, take thousands of years to grow to any size.
Also of course you have to tolerate high levels of cosmic radiation if you live anywhere on the surface or top few meters of the soil. Not a problem if you live deep underground.
Apart from that, has to be artificial habitats.
Basically Mars is not really much more habitable for humans than the Moon. It looks more Earth-ike but the similarity is rather superficial in many ways for humans at least.
For some microbes able to live in extreme cold and salt, or dry conditions with high levels of UV, and able to tolerate perchlorates, it might seem home-like enough for small populations to survive very much living on the edge. In Antarctica some microbes in similar conditions have such a slow metabolism they have lifetimes measured in thousands of years. That's for a single microbe. Also for some polar and high arctic lichens it may seem tolerable enough as a place to live, if they can cope with the high UV and take up humidity exploiting the 100% humidity at night when the atmosphere gets so cold it can dip below the freezing point for dry ice.
About the Author
Robert Walker
Writer of articles on Mars and Space issues - Software Developer of Tune Smithy, Bounce Metronome etc.Studied at Wolfson College, Oxford
Lives in Isle of Mull
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