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23-December-2007, 01:32 PM
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Naked eyeball survival on Mars
A man could walk on Mars without a space suit, wearing just an oxygen mask, and survive.
But what would visual accuity be like in a CO2 atmosphere? Would the naked eyeball sting or smart in the Martian atmosphere? Does the human eyeball require to be in physical contact with external oxygen for its cells to survive long term? Would the astronaut require an oxygenated sealed eyemask? 
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23-December-2007, 02:04 PM
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| grant hutchison |
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This message has been deleted by grant hutchison.
Reason: Duplication
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23-December-2007, 02:12 PM
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A simple face mask would supply oxygen at Martian ambient pressure, which is too low to sustain life. You'd need a tight-fitting mask supplying oxygen at above ambient pressure, which would make it very difficult to breathe out. The higher pressure in your lungs would also interfere with your circulation by compressing your heart, and is high enough to push gas into your circulation or pop your lungs. And, although the partial pressure of the Martian atmosphere is just high enough at low altitudes to prevent water boiling near its freezing point, it's too low to prevent water boiling at body temperature. Water would boil off from your corneas, water vapour bubbles would form under your skin and in your venous circulation. It would be pretty much indistinguishable from vacuum exposure. Edit: But, in answer to your question, the cornea does get a lot of its oxygen by diffusion from the air, because it contains no blood vessels. In a more hospitable oxygen-free atmosphere, I guess you would slough your corneas after prolonged exposure. The early contact lenses had very low gas permeability, and caused hypoxic corneal damage if you kept them in for too long. Grant Hutchison
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23-December-2007, 05:05 PM
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Maybe you'd have to wear something like a scuba diving mask, at a minimum.
Edited to add, I forgot to mention temperature. Exposed skin would quickly freeze, I assume.
__________________
"I'm as accurate as any psychic. And I'm a cartoon!" -- Squidward "Arrrgh, the laws of physics be a harsh mistress!" -- Bender
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23-December-2007, 05:06 PM
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__________________
"If you think the LHC will create black holes, you might as well believe Hobbits are at the bottom of your garden."- Dr. Mike Inglis Rovers forever! - ToSeek "Carl Sagan sent a message to ET, Neil Armstrong walked in the Sea of Tranquility Steve Squyers built Spirit and Opportunity Dan Haylen upchucked in zero gravity." -Brent Simon, The Space Camp Song
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23-December-2007, 05:16 PM
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 So, this previous Grant Hutchison contended that you'd need to insulate your feet from the cold ground, but that the atmosphere was so thin it would not take away much heat by conduction or convection: you'd be effectively surrounded by a pretty good vacuum flask, albeit one that was unsilvered. Your main surface losses (barring those cold feet) would be by radiation. So it seems like it might not be that difficult to stay warm. Grant Hutchison
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23-December-2007, 05:24 PM
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__________________
"If you think the LHC will create black holes, you might as well believe Hobbits are at the bottom of your garden."- Dr. Mike Inglis Rovers forever! - ToSeek "Carl Sagan sent a message to ET, Neil Armstrong walked in the Sea of Tranquility Steve Squyers built Spirit and Opportunity Dan Haylen upchucked in zero gravity." -Brent Simon, The Space Camp Song
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23-December-2007, 05:31 PM
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It's pretty much indistinguishable from the Moon. Grant Hutchison
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23-December-2007, 05:42 PM
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__________________
"If you think the LHC will create black holes, you might as well believe Hobbits are at the bottom of your garden."- Dr. Mike Inglis Rovers forever! - ToSeek "Carl Sagan sent a message to ET, Neil Armstrong walked in the Sea of Tranquility Steve Squyers built Spirit and Opportunity Dan Haylen upchucked in zero gravity." -Brent Simon, The Space Camp Song
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23-December-2007, 11:43 PM
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As Grant said, the surface pressure on Mars is about 0.1 psi, vs Earth's 14.7 psi. Mars is closer to lunar vacuum than any normal earth environment.
A healthy, trained, conditioned mountain climber at the summit of Mt. Everest (29,000 ft) can survive with an oxygen mask. A very few people have summited Everest without oxygen, although the death rate is very high. In theory using positive-pressure breathing (pure O2 is forced into your lungs, you exert yourself to exhale), survival is possible up to about 50,000 ft. At that altitude, atmospheric pressure is about 1.7 psi, 17 times that on Mars. The absolute limit without a pressure suit or equivalent is the "Armstrong Line", (about 62,000 ft): http://en.wikipedia.org/wiki/Armstrong_Limit At that altitude atmospheric pressure is the same as vapor pressure of water at 98.6F. IOW fluids in the unprotected human body will boil. Pressure at 62,000 ft is about 0.9 psi, or 9 times that of Mars. That explains why survival on Mars requires a pressure suit.
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24-December-2007, 02:36 PM
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(clue - it's not 'yes') Doug
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26-December-2007, 04:26 AM
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 ) May we assume if he is at 100,000 feet he is not wearing street clothes? IMO, he wouldn’t need a space suit, or even a pilots pressure suit. A simple spandex body suit should do it.
__________________
Reality: What a concept!……………………..><Ç(((Ç°>
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26-December-2007, 04:35 AM
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Even at 100,000 feet, I wouldn't be caught dead in spandex 
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26-December-2007, 05:27 AM
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I don’t think this was supposed to be a fashion discussion.
__________________
Reality: What a concept!……………………..><Ç(((Ç°>
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26-December-2007, 08:40 AM
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  I like Kim Stanley Robinson's series personally, though I am not of a level to know if EVERYTHING in it is possible. He had the Mars-o-nauts outside in a runner/athletic version of a high altitude pilots suit with a whole lot more technology involved. I got the impression that between the layers of cloth/whatever was a carbon nano-tube full body version of a chinese finger trip. So not a pilot suit, but thin, pressurized and not terribly insulated all the same. Also, they had helmets or masks of some sort to keep their faces intact.
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None to speak of Last edited by man on the moon; 26-December-2007 at 08:41 AM. Reason: d'oh
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26-December-2007, 11:11 AM
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"A man could walk on Mars without a space suit, wearing just an oxygen mask, and survive. " The only valid response to that is that no, he couldn't. No point exercising semantics on this - the OP was assuming something that's simply not true. Doug
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26-December-2007, 12:41 PM
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To let you breathe a high enough oxygen pressure to keep you alive, it would have to compress your entire body at that pressure. The pressure involved is about the same as your normal arterial pressure. This makes the business of getting in an out of the suit hazardous and complicated. It also requires quite exquisite tailoring to your body surface. We had some discussion about this on a previous thread. Van Rijn provided a good link to a NASA technical document, describing development work on such a compression suit: http://chapters.marssociety.org/winn...tivitySuit.pdf I summarized some of the key points in that study as follows: Quote:
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26-December-2007, 03:19 PM
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You also can't survive with a simple spandex body suit. It's theoretically possible a highly sophisticated counter-pressure suit could allow survival -- however that is NOT a simple spandex body suit. E.g, a medical compression stocking (say for varicose veins) might be 20-30 mm Hg pressure (0.38 - 0.58 psi). A class III compression garment (the tightest kind) is about 40-50 mm Hg (0.77 - 0.97 psi). It is VERY tight and quickly becomes uncomfortable. Also they are only available for small areas, like a sock. By contrast about 150 mm Hg (2.9 psi) is needed for survival on Mars -- over the entire body. That's why NASA doesn't buy spandex leotards from an athletic supplier and use those. While an approximate description of a counter-pressure suit might be "sort of like a spandex suit", in fact the required pressure is MUCH higher. This means all the issues of doffing/donning, pinching, maintaining uniform pressure during movement, etc. are vastly harder. Imagine you're on Mars, wearing the tightest available commercial spandex suit. You have a positive-pressure O2 regulator (you work to exhale, upon relaxation it forces O2 into your lungs). You'd nonetheless be dead from ebullism within a few minutes: http://en.wikipedia.org/wiki/Ebullism. Separately, I wonder how long you could survive on Mars with an old-style military "capstan" counter-pressure suit? http://www.astronautix.com/craft/s2pesuit.htm
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