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Message: <blockquote data-quote="Marius Delphus" data-source="post: 513221" data-attributes="member: 447">Okay, my Outer Space Physics and Human Biology are a little rusty, so anyone who knows better should feel free to step in any time.First, let's talk about zero-g, or "microgravity" as it's referred to while in orbit. Liquids exposed to microgravity environments do tend to collect in spheroid shapes and float around, as film showing astronauts having fun with their Tang (or whatever <img src="https://cdn.jsdelivr.net/joypixels/assets/8.0/png/unicode/64/1f642.png" class="smilie smilie--emoji" loading="lazy" width="64" height="64" alt=":)" title="Smile    :)"  data-smilie="1"data-shortname=":)" /> ) proves. We don't fully understand the ramifications of spending extended periods in microgravity, but we have a number of good guesses.<a href="http://spacelink.nasa.gov/products/Space.Food.and.Nutrition/microgravity.html" target="_blank">http://spacelink.nasa.gov/products/Space.Food.and.Nutrition/microgravity.html</a> (the text, not the pic)<a href="http://www.space.edu/projects/book/chapter31.html" target="_blank">http://www.space.edu/projects/book/chapter31.html</a>Second, blood takes its color from the oxygen incorporated into it; the level of atmospheric oxygen doesn't change the color of blood. Blood changes color to "crusty brown" as it *dries.*<a href="http://www.madsci.org/posts/archives/dec96/839903302.An.r.html" target="_blank">http://www.madsci.org/posts/archives/dec96/839903302.An.r.html</a><a href="http://www.seps.org/oracle/oracle.archive/Life_Science.Anatomy/2001.02/000981693349.24712.html" target="_blank">http://www.seps.org/oracle/oracle.archive/Life_Science.Anatomy/2001.02/000981693349.24712.html</a>Third, the primary hazard to an exposed human body in outer space is the zero atmospheric pressure ("hard vacuum"), after which follows the ultra-cold {EDIT - extreme} temperature and, if the unfortunate soul somehow survives *those* two hazards, there's often a hefty dose of hard radiation to deal with.<a href="http://imagine.gsfc.nasa.gov/docs/ask_astro/answers/970603.html" target="_blank">http://imagine.gsfc.nasa.gov/docs/ask_astro/answers/970603.html</a>So to answer the question we leave aside the fact that a spacesuited character in hard vacuum is facing a serious and quickly lethal emergency if the suit is punctured (venting the suit's air and pressure into space) and the character is bleeding (venting blood into space). <img src="https://cdn.jsdelivr.net/joypixels/assets/8.0/png/unicode/64/1f600.png" class="smilie smilie--emoji" loading="lazy" width="64" height="64" alt=":D" title="Big grin    :D"  data-smilie="8"data-shortname=":D" />So the color of the blood will vary between dark red, venous blood and bright red, arterial blood depending on what's been punctured. Assuming our poor victim is in a hard vacuum + microgravity environment, the blood will most likely spray forth from the suit (remember, blood is under pressure) and collect in large droplets. If we now assume our hapless astronaut is in the cold of outer space, I'm inclined to guess the droplets will freeze rather quickly, but that may {EDIT - does} depend on how much radiant heat is available from the nearest star.</blockquote>

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