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How long can a naked human survive at the surface of the Mars planet?

For instance, let's say a worker's base takes fire while he sleeps, the building is totally ablaze and he can do nothing but run to the emergency building 200 meters away without any respiratory equipment, pressure suit, UV protections or anything.

Maybe a human could survive for a rather long time, and apnea time is the real limiting factor?

Climate:

  • Temperature: 27 °C to −50 °C (base is at a rather warm location, on Equator)
  • Pressure: 0.006 bar (Earth: 1 bar)
nic
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  • I think two things might be the issue: 1) lack of atmospheric oxygen and 2) the dust. – blep May 09 '13 at 06:39
  • @dd3: Don't hesitate to propose an answer around this :-) – nic May 09 '13 at 07:14
  • Frost Burns are likely to be the real killer here. Lack of blood flow due to constricting vessels means that cells and tissue could freeze solid from the dramatic temperatures –  May 09 '13 at 11:22
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    "You should only ask practical, answerable questions based on actual problems that you face" - I'd take care if you're planning to test this ;-) – Rory M May 09 '13 at 19:10
  • @RoryM: It is actually a problem that might be faced: http://mars-one.com Of course, more serious research must be performed eventually :-) – nic May 10 '13 at 02:06
  • @NicolasRaoul ah glad im not the only one aware of this site! You planning to apply hence the question? –  May 10 '13 at 07:56
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    I did wonder if it was related to Mars One :L – Rory M May 10 '13 at 12:41

4 Answers4

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Long story short, the astronaut probably wouldn't make it, and would first loose consciousness then suffocate.

There is a lot of myth and hollywood dramatization regarding this kind of thing. Here are some:

  1. You will explode. This is just ridiculous. The skin is air tight (relatively speaking). It is also very elastic and can pull and bend quite a great deal before tearing. Through quite a few, equally durable, tissues, it is connected to the bones, which are unaffected by negative air pressure.
  2. Your blood will boil. The circulatory system is also a closed system. It is not directly exposed to the environment. Also, the blood pressure in a healthy person is averaged around 100 mmHg and Earth's atmosphere at sea level is 700 mmHg. There is already a massive disparity, yet Earth's atmosphere doesn't go pouring into our veins at random. Likewise, the blood in a person's veins won't go pouring out into the atmosphere simply because the pressure is extremely low.
  3. Any air in your lungs will be forcibly sucked out of you. Again, this is a closed system, if you hold your breath. As long as you don't try to breathe there is nothing forcing the air from your lungs.
  4. Your eyes will be sucked from their sockets. Thank you Total Recall (the original) for this myth. The eyes are very firmly in place. You might feel a pull on them, but they aren't going anywhere.

Absolutely none of these would happen in the vacuum of space and certainly not on the Martian surface.

Here's what will happen:

Any liquid material on the surface of your body will vaporize. All sweat, saliva (if you open your mouth), water in the mucous, and tears on the eyes, will nearly instantly vaporize. It would be quite uncomfortable, especially the eyes, but very survivable. Long term exposure to a vacuum might damage the eyes eventually, but in this scenario there are far more pressing matters.

The negative pressure may also cause your eardrums to rupture. Try to imagine the feeling your ears get on the plane at 30 thousand feet times about 100. Since you can't close your ears, plugging them with your fingers may help, but likely just postpone the inevitable pressure disparity, which will lead to at least great discomfort and possible drum rupture.

If you had the chance, you should take a deep breath before jumping out and avoid trying to breathe at all costs. Opening your lungs for a breath would very quickly draw whatever breath you had in them out into the atmosphere and also vaporize any fluid that was in them. Considering the rapid pace of this event, you would surely have permanent damage from this and begin suffocating and will die in a minute or two unless you get medical attention. There seems to be conflict in the procedure for this, with some sources suggesting that emptying your lungs would be better to avoid this. Considering the astronaut in your example is about to do a 200 meter dash he is going to need all the O2 he can get.

The cold is also a treacherous factor. At -50C the heat from your body would dissipate so rapidly that it would likely be very debilitating, perhaps causing you to seize up and clutch your extremities to your chest. It would also be excruciatingly painful. It might cause you to fall into shock. In a total vacuum however, this does not exist. A vacuum is actually very insulating, but on Mars' what little atmosphere is there is enough for you to feel the chill.

The lack of oxygen and high CO2 would be what would eventually kill you. You would eventually try to breathe and loose consciousness within a breath or two (or you might loose consciousness first then your body would try to breathe naturally). Your body would try to keep you alive as long as possible by pumping your heart faster and increasing your blood pressure, but your heart would eventually fail and you would die within seconds after that.

Evaluating your particular scenario

There are first a few things about the scenario that seem unlikely.

  1. The astronaut would not be naked. They remain in some of their protective gear in case of emergencies like this. He would have some protection against the cold if he had to run out without it.
  2. Certain things like extinguishers are always nearby. The idea that one was unreachable is a little silly.
  3. Space vehicles, shuttles, and buildings all are compartmentalized like a submarine. They could simply close off the affected areas.
  4. Fire only burns in the presence of oxygen (with few exceptions). After being closed off, compartments can be decompressed, halting the fire immediately. They can then begin refilling them with breathable atmosphere. This poses the same vacuum problem if the astronaut is in the affected area, but he won't be trying to run across the surface naked. People have survived rapid decompressions before without a single injury, as listed in my second source, however, others have never regained consciousness.
  5. Assuming you made it to the other building, they usually only open from the inside. So unless someone saw you coming and opened the door for you, your last minutes would be better spent desperately fighting the fire until it consumed you rather than banging on the neighbor's door.

But let's say all of this breaks down and poor Astronaut Joe finds himself making a mad, streaker's dash across the Martian surface.

We should assume that our astronaut is both quite athletic and knowledgeable about the environment outside of his shelter, knowing that he should take a deep breath before heading out, but literally has no time to grab a shirt, goggles, breathing mask, or anything. Just him and Mars.

If he's lucky, it's not too cold and he doesn't seize up and fall into the fetal position within a few steps. Let's say it's -20C, which is pretty darn cold, but tolerable for a minute or two. I next see him flailing across the surface, trying to run in Mars' low gravity (no easy task). He begins to loose vision as a cloud of steam of what should be tears pours from his dry eyes. His eyelids then begin to stick to his eyeballs because there is no longer any lubrication. He is desperate to reach the other building, and his movements get more and more erratic, as his body is rapidly using all of the available oxygen. All the while, he is still holding his breath, knowing that if he attempts to breathe he will likely collapse within seconds and perish. But the more he struggles to make it, the more his innate urge to breathe overpowers his conscious thought to prevent it. Eventually, against his own willpower, he gasps and attempts to inhale deeply. He takes two or three dying breaths, if they can be called that, then falls to the ground unconscious. He dies shortly after when his heart stops and his brain tissues die.

The whole ordeal lasts under 30 seconds and he is 100 meters at most away from his shelter. If he did get lucky and actually made it to the other building, he would likely have frostbite over much of his body, permanent damage to his eyes and ears, and possibly deadly exposure to cosmic rays.

The event would be very similar to being drug by a fishing line to the bottom of the sea and drowning.

Sources:

A fun questionnaire to see how long you would last in space
What really happens in a vacuum

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    Temps vary between 80F and -199F, averaging -64F. So while it's cold on average, the temperature could certainly be reasonable enough to not be a factor, and it's reasonable to assume that a habitation would be on the equator, so would be warm at least at midday. I'd argue a fit, healthy, trained person with time to aerate in the air lock and who's life depends on it could hold their breath for three minutes at a push. At walking pace on earth, it takes almost three minutes to walk 200m. Cutting it close, but it's a problem of low pressure, gravity, and oxygen, not necessarily temps. – Dewi Morgan Aug 20 '15 at 19:44
  • Then again, I'm going by my experience while swimming - and the diving reflex is a thing, so you may be right about the 30 secs, after all. – Dewi Morgan Aug 20 '15 at 19:54
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    I joined this community just to add this comment, this answer is wrong in so many ways, please disregard it and don't consider it's length as merit for it's correctness. @fredsbend, please consider deleting - – ccook Feb 17 '16 at 01:43
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    @ccook I certainly will consider deleting it ... once you show why it's wrong. If it really is wrong in "so many ways" then I think an answer showing what is the correct answer would be the best course. –  Feb 17 '16 at 02:28
  • @fredsbend, in short: 1. chest cavity explodes from 14 psi over large surface area of lungs. 2. It's a gauge pressure difference, your blood pressure is higher than atmospheric, second, gases release due to partial pressure releasing dissolved gases. This is called the Bends. 3. This is just physically wrong, just like a balloon you will expel the gas in your lungs through your mouth if you dont rupture elsewhere. You cannot hold 14 psig. 4. This is true because your head and eyes are made of liquids, which are incompressible (right conclusion, wrong reason). [1 of 2] – ccook Feb 17 '16 at 18:15
  • @fredsbend [2 of 2] for the what will happen paragraphs 1. Closing your mouth will not allow you to hold any appreciable pressure. Try getting a pressure gauge to read 1 psig by blowing on it. 2. This is conjecture, where ironically, opening your mouth serves to protect your eardrums (yawning to fix ear pain in flight. 3. This is against all general advice. 4. Thermal and pressure scales are dramatically different, one is at the speed of sound, the other takes many minutes - pressure gets you not temperature. 5. It takes more than a breath or two to run out of oxygen (its pressure related) – ccook Feb 17 '16 at 18:18
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    @fredsbend and see this for cases showing survival in vacuum on the scale of minutes: http://www.scientificamerican.com/article/survival-in-space-unprotected-possible/ – ccook Feb 17 '16 at 18:18
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    @ccook Thank you for responding. From the article: "Vacuums are indeed lethal: Under extremely low pressure air trapped in the lungs expands, tearing the tender gas-exchange tissues. This is especially grave if you are holding your breath or inhaling deeply when the pressure drops." I believe one of my sources mentions this, yet also mentions it may not be the case. Whether to hold your breath or not seems to be a point of contention. I suggest a breath because he's about to sprint; he'll need the oxygen. –  Feb 18 '16 at 23:22
  • As for the rest of your comments, I'm having trouble seeing what you are referring to. Perhaps starting a chat room would be best, then you can quote the part of the answer you object to, then list your objections. –  Feb 18 '16 at 23:22
  • And, yes, some have survived minutes of vacuum exposure, but all I know of have lost consciousness in under 30 seconds. –  Feb 18 '16 at 23:24
  • Mars is at about 1% Earth atmosphere. Space is much less and the pressures in the tests that article mentions says did it at about 0.25%. I figure the extra pressure allows a bit more time of consciousness. Indeed, it is true that he may lose consciousness before trying to breathe, but that paragraph is a dramatization, not necessarily textbook reaction. All the other stuff in the answer is. –  Feb 18 '16 at 23:30
  • Perhaps a few things can be clarified, specifically, you're likely to lose consciousness in the first 30 seconds due to the pressures, but we don't know for sure if the extra pressures on Mars is enough to keep you conscious longer. I may edit this weekend if I have time. –  Feb 18 '16 at 23:33
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    @fredsbend When doing an emergency ascent from 10m (2 atm), divers are told to exhale constantly and steadily to prevent lung over-pressure. (See Pulmonary Barotrauma, CESA). – Basic Jun 02 '16 at 18:24
  • I really like the effort put into this answer, and it was eye-opening for me in several ways. However, I still gave a downvote because there was still a big issue unresolved: "closed system, if you hold your breath. As long as you don't try to breathe there is nothing forcing the air from your lungs...Absolutely none of these would happen in the vacuum of space". Actually, air would still get out. There are more orifices other than one's mouth, and they can never be all closed perfectly tightly, especially since the man is naked. – rhyaeris Aug 15 '17 at 13:06
  • @rhyaeris If you hold your breath, how much air can actually escape in 30 seconds. Half a breath? A quarter breath? I'm betting much smaller. Is it significant enough to mention? –  Aug 15 '17 at 15:11
  • @fredsbend https://m.youtube.com/watch?v=pm6df_SExVw please see 1:53. In vacuum, air can escape quickly through several orifices, simply due to the vast pressure difference. – rhyaeris Aug 16 '17 at 06:41
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One other important event that can kill the person is that the atmospheric pressure on Mars surface is less than one percent that of earth at ground level. Suddden exposure to extremely low atmospheric pressure will immediately release dissloved gases within blood and and other body fluids as bubbles and the individual is likely to get a very severe form of Decompression sickness as in divers coming up too fast. The person is likely to lose conciousness and die within a couple of meters after leaving the shelter.

Ram Manohar M
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  • That sounds like the fastest factor so far, thanks! Is there any reference or research on the topic? Accepting this answer. – nic Aug 25 '13 at 02:28
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    The pressure difference human normal atmosphere - near vaccuum is about 1bar or the same as 10m of water. Are you sure this is enough to cause divers sickness? – mart Aug 26 '13 at 13:17
  • @mart When ascending from 10m, divers will usually do a stop at 5m, then 3m to avoid any issues. That said, an emergency swimming ascent from 10m without stopping is part of the training (but obv not recommended). One thing to consider is that short (air) dives often don't last long enough for nitrogen levels to reach saturation levels in tissue, so presumably the situation on Mars would be worse. – Basic Jun 02 '16 at 18:19
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Less then a minute breathing in the atmosphere (and a very painful death). Mars' atmosphere is >95% CO2 with only trivial O2. These are atmospheric conditions similar to those used to euthanize laboratory animals. He probably wouldn't even make it 200 meters before suffocating.

kmm
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    i havent done the math but you can hold your breath longer than a minute, i think you would die of freezing to death long before you suffocated though –  May 09 '13 at 12:36
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    Certainly humans can hold their breath longer than a minute, but can they run 200 m while holding their breath given the elevated heart rate and blood pressure resulting from general sympathetic response resulting from their sleeping quarters being on fire? They won't freeze at 27 C. – kmm May 09 '13 at 14:05
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    27 degrees is the highest recorded temperature on mars, the average temperature of the surface is -55 degrees C –  May 09 '13 at 14:11
  • the time to death after being submerged in ice water is not that short. I'd say asphyxiation (< 5 minutes) would do it first. This is kinda a bar-bet conversation... but still interesting. – shigeta May 09 '13 at 18:05
  • @kmm: "These are atmospheric conditions similar to those used to euthanize laboratory animals" ← Very interesting! That should give us a pretty good idea of the time, right? Has this euthanisia method ever been used on a big monkey for instance? How long is usually necessary? – nic May 10 '13 at 02:11
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    @shigeta ice water is around about 0 degrees, this is -55 degrees were talking about, the difference will yank that heat out of you in seconds –  May 10 '13 at 07:56
  • If the atmospheric conditions are similar to those used to euthanize animals, why is it such a painful death? – Madara's Ghost Aug 24 '13 at 20:37
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    the article you link also mentions that mars' atmosphere has 0.6% the pressure of earth' atmosphere, so you only get 0.6% of the CO2 per lungful as the lab animals on earth - I doubt that you get enough to die of poisoning before freezing. – mart Aug 26 '13 at 13:20
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Coming up with the exact number is likely to be very difficult but i would put it in the range of 1-2 minutes to impossible.

Let's ignore the lack of oxygen and assume you could hold your breath long enough to reach the safe haven.

The extreme cold would easily drop your core temperature to the realm of severe hypothermia within minutes.

If that doesn't kill you first then the extreme cold has already caused your blood vessels to shrink before you can even take more than a few steps. On top of this the extreme cold is enough to freeze solid any muscles and other tissue, making movement painful / difficult / impossible.

Now lets assume that through some miracle none of that kills you and you make it to the safe haven. The distinct lack of a magnetic field around the planet exposes you to high levels of UV radiation. Being completely naked and having your entire body exposed to this level of UV is likely to cause lots of mutations throughout your cells. Which in itself will kill you.

So your chances aren't looking good for anything beyond a minute!

  • good point - big difference between sunlight and day/night conditions, but there is a limit to how quickly the body can lose heat.... – shigeta May 09 '13 at 18:06
  • Interesting! At http://www.sciencebuddies.org/science-fair-projects/project_ideas/MicroBio_p017.shtml I see that UV kill bacteria in 6 days, I guess it Mars UV are more violent but would UV alone really result in such a sudden death? – nic May 10 '13 at 01:52
  • @NicolasRaoul i will find the link, the UV exposure levels on mars are something like 10 thousand times greater than what we are exposed to on earth –  May 10 '13 at 07:55
  • You have a point RhysW, it sort of depends on whether you are talking about the most extreme conditions, average , or what. – shigeta May 10 '13 at 18:17
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    U.S. standards limit an astronaut’s lifetime radiation exposure to 1 Sievert and http://news.discovery.com/space/mars-radiation-astronauts-health-threat-130530.htm says "even the shortest roundtrips to Mars would get radiation doses of about 662 millisieverts". While the number is impressive, it also means that UV-death won't occur before a few days, which means long after suffocation. – nic Jun 03 '13 at 08:07
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    http://www.hou.usra.edu/meetings/ppw2015/pdf/1011.pdf "The UV flux on equatorial Mars has been modeled by several teams [e.g., 1,6,7] and yields approximate fluence rates for UVA(400-320 nm), UVB(320-280 nm), and UVC (280-200 nm) of 38, 8, and 3 W/m2at the mean orbital distance from the sun. These fluence rates are then decreased or increased by ~18% at aphelion and perihelion, respectiveluy[sic], during the martian orbit" That's Watts, not kiloWatts. Fine for a stroll, but you will get sunburn from prolonged exposure. UV is not a significant risk in this scenario. – Dewi Morgan Aug 20 '15 at 20:19