# What will happen to a human being exposed to Martian atmosphere?

Mark Watney, in the movie The Martian, says that,

If the HAB breaches, I'm just gonna, kind of... implode.

The corresponding novel, by Andy Weir, says he will explode (as pointed out by @MikaelSundberg).

I think he will neither explode, nor implode, but simply die of cold and asphyxiation.

Can anyone scientifically explain what will happen?

PS: The HAB is a NASA designed habitat for humans on Mars.

• The strange thing about this, is that in the book Mark actually says 'explode' not 'implode'. I wonder why it was changed in the movie. – Mikael Sundberg Dec 30 '15 at 23:26
• @MikaelSundberg as simplicis points out, due to the low air pressure, the air will be sucked out instantly, causing lungs to implode. His veins and skin will bulge, but the human body seems to be capable of handling the extra pressure. I think he will freeze before the pressure causes him to explode. I think the book had it wrong and they corrected it in the movie. – ps95 Dec 31 '15 at 1:04

The Martian atmospheric pressure is approximately equal to $0.6\%$ of Earth's mean, at sea level, mostly consisted of $CO_2$ ($98\%$).

This is equivalent of pressure at altitude of approximately $17 km$ in the Earth atmosphere, with boiling point $30 ^oC$.

The pilots use oxygen masks at altitudes $> 4km$, so even if Mars's atmosphere was entirely of $O_2$, people wouldn't survive.

Regarding the temperatures on Mars, they vary from $-150 ^oC$ to $+20 ^o C$.

Consequently, sure death by asphyxiation and depending on the location and season, instant or later freezing, which will be accelerated by the low boiling point, especially if there is no suit.

• The movie is scientifically correct, so can you please elaborate on the imploding part as well? I don't think they made an error – ps95 Dec 25 '15 at 20:58
• @prakharsingh95 The implosion part is probably related with the rapid body fluid evaporation that could make the human body squeeze and dry. – Ziezi Dec 25 '15 at 21:06
• Yeah, that makes sense. I had though imploding due to air pressure only, which had me confused. Accepted your answer, Thanks! – ps95 Dec 25 '15 at 22:29
• The pressure of the atmosphere (or vacuum) doesn't matter to the biological effects. Human skin and tissue are very strong and they keep the internal pressure much higher than the atmospheric pressure under these conditions, i.e. the atmospheric boiling point simply doesn't matter. The essential effect is, as you said, near instant asphyxiation. – CuriousOne Dec 25 '15 at 23:48
• You have to model the human body as a series of tissues that are encapsulating each other. There is the dermis, then a fatty layer, then connective tissue that holds the muscles together etc. Each of these layers can expand somewhat to allow for movement, but they are also holding the body together. If they didn't, we would be like jellyfish and basically rupture from our internal pressure. To prevent that the skin and connective tissue have to withstand significant pressure beyond the blood pressure. That will keep a body intact and the blood from boiling. – CuriousOne Dec 31 '15 at 3:57

The Martian atmosphere is effectively vacuum. He would be unconscious in less than 20 seconds and the he will end up freeze dried.