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Various sci-fi movies treat Mars atmosphere differently, anywhere between "you just need oxygen rebreather" and "Your eyes will pop out and your head will explode". Meanwhile, I haven't seen any solid scientific data on human surviving requirements in Mars conditions.

Surely the suit would have to be warm, probably with active heating or at the very least good insulation, like aerogel. Surely one would need to at least provide oxygen, probably the neutral gas too to prevent acidosis from Mars' CO2 in its atmosphere. But how would human body react to the pressure? I'm aware humans can survive in pressures considerably lower than normal, with correspondingly increased oxygen content - Apollo cabin pressures were about 25% of Earth's atmospheric pressure. How is the situation on Mars?

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    $\begingroup$ By Earth atmospheric pressure, I suppose you mean sea level pressure? Pressure at Mt. Everest is ca. 1/3rd of sea level pressure, and clearly that's not a problem either. $\endgroup$ – gerrit Jul 24 '13 at 15:56
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    $\begingroup$ @gerrit: "1 atmosphere" if you allow such non-SI units. $\endgroup$ – SF. Jul 24 '13 at 16:56
  • $\begingroup$ I won't post this as an answer because I'm not sure if it really proves anything, but Felix Baumgartner jumped from an elevation with pressures similar to the Mars surface, and his suit was pressurised. $\endgroup$ – gerrit Jul 24 '13 at 17:23
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    $\begingroup$ Mars' atmosphere provides only slightly more pressure than the water's triple point (where it can only be in solid or gas phase), so your blood wouldn't literally boil, but close enough - similar to opening a bottle of pop soda and the soluble gases forming bubbles. In a sense, a bit like decompression sickness, only happening a lot more rapidly than we usually see with divers. Also, the average temperature on Mars is −63°C, and a pressurized suit would help insulating from rapid heat dissipation. The way Total Recall shows it is IMO quite accurate. You'd definitely need a pressure suit. ;) $\endgroup$ – TildalWave Jul 24 '13 at 17:34
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    $\begingroup$ @TidalWave: The more pressure delta you want to keep in the more durable (thicker, heavier) the costume must be. Also, the higher the pressure inside the more resistance of bending your limbs you must overcome - normally, the suit, like a bloated balloon "gravitates" towards certain shape and to move you must overcome its resistance. More pressure = more work to overcome it. $\endgroup$ – SF. Jul 24 '13 at 21:01
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Yes

The atmospheric pressure on Mars is about 0.6% of Earth's sea level pressure. That's about 0.6 kilopascals (0.087 psi). Whereas even one of the highest points on earth, Mount Everest is 33.7 kilopascals (4.89 psi). That means Mount Everest has about 56 times the atmospheric pressure of the surface of Mars.

Humans wouldn't survive very long in those sorts of conditions. According to this graph from NASA, .087 psi puts us below the "Bubbles in blood" level:

enter image description here

(Note the graph goes from high pressure at the top to low pressure at the bottom)

Even Everest is just barely in the safe region for humans. The graph assumes the individual is breathing the atmosphere they're in, which isn't the case in your proposed question.

There is evidence that a person could survive briefly.

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    $\begingroup$ lbs/sq in. Oh, NASA, when will you cease your silliness! $\endgroup$ – SF. Jul 24 '13 at 21:03
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    $\begingroup$ Explanation of downvotes is polite and beneficial to everyone. $\endgroup$ – MichaelHouse Jul 24 '13 at 23:54
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    $\begingroup$ @SF. lbs/sq in, a.k.a. psi isn't exactly a "silly" unit; it's use is still extremely widespread. $\endgroup$ – Nick T Dec 11 '13 at 4:50
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    $\begingroup$ @NickT: 1 yard is the distance from king's nose tip to his extended hand's fingertips. It is quite widespread too, which does not preclude its silliness. $\endgroup$ – SF. Dec 11 '13 at 7:57
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    $\begingroup$ @SamtheBrand The suit doesn't need to be air pressurized. It would be possible to use a compression suit applying mechanical pressure to the skin, similar to a space activity suit. Unfortunately they still have a number of problems. Keeping even pressure on every bit of surface area (especially concave areas of the body like the groin and arm pits) is very difficult. Body fluids tended to pool in areas where sufficient pressure is not applied. Without such pressure the skin expands and can be damaged. $\endgroup$ – MichaelHouse Jan 30 '14 at 19:19
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There is no requirement for the suit itself to be pressurized.

There is a requirement for some pressure on the skin to prevent vacuum bruising. That can be provided by either of two means - fluid pressure from the environment, or mechanical pressure.

Current "bleeding edge" designs are a wire-reinforced elastic material, with a pressurized helmet that seals to the shoulders. The skin is actually encountering 0 atmospheric pressure, and the suit is porous to allow sweat to escape, but maintains even mechanical counter-pressure to the 3 or so pounds per square inch needed to avoid vacuum injury.

Note that eye damage from vacuum isn't instant, either - but is fairly rapid. Individuals in vacuum experiments accidentally exposed to vacuum experienced immediate eye irritation due to rapid loss of moisture, but all made full recoveries from momentary exposures.

Likewise, lung damage is rapid, but not instant, and is mostly due to drying and edema. Several minutes of extremely low pressure on skin resulted in profound edema, but no lasting injury, for the early weather ballon jump tests.

http://spaceindustrynews.com/mits-next-mars-space-suit/ http://www.edudemic.com/2012/09/mit-researcher-unveils-incredible-new-mars-space-suit/ http://www.nasa.gov/offices/oce/appel/ask/issues/45/45s_building_future_spacesuit.html

http://www.universetoday.com/66061/early-nasa-vacuum-chamber-test-gone-wrong/ http://imagine.gsfc.nasa.gov/docs/ask_astro/answers/970603.html

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You will need a full helmet. Your eyes, ears and sinus passages are sensitive to low pressures and are wet. Low pressure would cause the moisture in your eyes, ears, nose to boil and you would damage your ear drums. So certainly fully pressurized helmet. But the rest of your body is pretty good at keeping the inside in. You circulatory system maintains it's pressure, so your blood won't boil. You are breathing pressurized air so that keeps your internal pressure where it belongs. I think beyond that you need some insulation to keep you from losing too much heat and you need clothing to protect your skin from the higher UV that will get through a thinner atmosphere. I'm pretty sure that a pressurized helmet, a compression undergarment, and possibly additional insulation, like Antarctic gear, as needed depending on the ambient temperature.

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