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efkelley
01-20-2011, 04:04 AM
Here's a fun one. Blood exposed to raw vacuum boils away in seconds. What color is the residue going to be? My guess is a dull red, similar to old, crusted blood.

And, would you see any vapor in the absence of an atmosphere to suspend it in?

I'd value any thoughts or opinions.

Fenika
01-20-2011, 04:14 AM
When there's blood gumming up my stew, it's foamy and reddish brown. Luckily it's easy to scoop out.

Whoever figured out the blood in a vacuum thing, prolly documented the color and if there was noticeable vapor. You need only shoot NASA an email... :)

Xelebes
01-20-2011, 04:26 AM
I would guess blue as that is what the colour of the hemoglobin deprived of oxygen.

Lhun
01-20-2011, 04:42 AM
It will look pretty much like frozen blood, since that's what'll remain. If you keep it warm, it still shouldn't darken quickly, since that's caused by chemical decay, not just the evaporation of water.

Astronomer
01-20-2011, 04:18 PM
I'm with Xelebes. More blue than red, since the oxygen (I think, anyway) would escape under a vacuum.

Lhun
01-20-2011, 05:28 PM
Did a little back-of-envelope calculation, after about 5% of the blood evaporates, the rest will be frozen (assuming it starts out at body temperature).
I'd need to know (well, remember probably) more about the way haemoglobin binds oxygen to know whether it will still release oxygen when frozen.

fireluxlou
01-20-2011, 05:39 PM
When there's blood gumming up my stew, it's foamy and reddish brown. Luckily it's easy to scoop out.

Whoever figured out the blood in a vacuum thing, prolly documented the color and if there was noticeable vapor. You need only shoot NASA an email... :)

I thought that wasn't blood. I thought blood was mostly drained when the animal was slaughtered and what you're seeing is water mixed with myoglobin.

LBlankenship
01-20-2011, 05:43 PM
>And, would you see any vapor in the absence of an atmosphere to suspend it in?

Shouldn't it be easier to suspend a vapor in a vacuum than in an atmosphere where it would dissolve away? It would depend on how much there was, I would think. How messy is the scene? :)

efkelley
01-20-2011, 10:41 PM
An atmosphere actually holds a suspension together until a current (wind or just Brownian motion) disperses the suspension beyond visual acuity.

This is a messy scene. A semi-fluid tungsten-steel kinetic round impacts an unarmored individual at 3000 meters per second. The round is fired from above, impacts the shoulder at a thirty degree angle to the body, and, more or less, rips him in half as the round spreads out. He doesn't gib or fall into halves exactly, but the overkill here is excessive.

I think I'm going to go with a bright red frozen splatter for now. In fact, come to think of it, any 'vapor' is just going to spread along the ground until it freezes as well. There's no atmosphere for it to suspend in. There would be some vertical motion due to heat, of course, but that certainly won't last long. Hmm. Need to think on that some more.

Lhun
01-21-2011, 01:19 AM
An atmosphere actually holds a suspension together until a current (wind or just Brownian motion) disperses the suspension beyond visual acuity.Vapour in a vacuum will certainly be visible (well, actually you'll see the gas in the vacuum), but it will very quickly disperse. There aren't any clouds that linger, since anything like that will be pushed quickly apart by brownian motion.

This is a messy scene. A semi-fluid tungsten-steel kinetic round impacts an unarmored individual at 3000 meters per second. The round is fired from above, impacts the shoulder at a thirty degree angle to the body, and, more or less, rips him in half as the round spreads out. He doesn't gib or fall into halves exactly, but the overkill here is excessive.I'm not sure how a 3km/s impact would affect the slug, but a person would certainly be splattered all over the area. The faster an impact gets, the shallower the impact crater since the lateral shockwave gets stronger.

I think I'm going to go with a bright red frozen splatter for now. In fact, come to think of it, any 'vapor' is just going to spread along the ground until it freezes as well.You don't really get vapour like in an atmosphere. The usual vapour happens because water (for example) evaporates to gaseous form, which looks much like air, but then cools down below boiling temperature once it mixes with cooler air, resulting in a lot of very tiny droplets suspended in the air. In a vacuum, it simply stays gaseous. If there's enough water boiling, you'd still see something like vapour, since the gas will be visible compared to vacuum. The cloud of gas will quickly spread out in all directions due to internal pressure.

There's no atmosphere for it to suspend in. There would be some vertical motion due to heat, of course, but that certainly won't last long. Hmm. Need to think on that some more.Gases rising due to heat only happens because of different buoyancy in the surrounding gas. No such thing in a vacuum.

efkelley
01-21-2011, 01:43 AM
Oh, by heat rising I meant some particles are going to have some motion upward because the molecules were heading that way. Mostly though, I think this isn't going to contribute much 'lift' at all.

I have a feeling the vapor is just going to spread at ground level until everything is frozen. It's going to spread very quickly since there's no atmosphere to impede it, and it's going to freeze very quickly as the ground temperature (on Ganymede) is -150c. Say, a few seconds at most.

Yep. Splat.

Lhun
01-21-2011, 02:31 AM
Oh, by heat rising I meant some particles are going to have some motion upward because the molecules were heading that way. Mostly though, I think this isn't going to contribute much 'lift' at all.That's kinda what happens in evaporation. ;) You heat the substance until the brownian motion overcomes the cohesive forces of the liquid (van der Waal's mostly).

I have a feeling the vapor is just going to spread at ground level until everything is frozen. It's going to spread very quickly since there's no atmosphere to impede it, and it's going to freeze very quickly as the ground temperature (on Ganymede) is -150c. Say, a few seconds at most."Frozen" doesn't really apply to gases. The molecules are isolated anyway, they can only take solid form if there are enough others in close proximity to form a crystal grid (That's why boiling temperatures fall the lower the pressure is). In a vacuum, you will get evaporation of a liquid until the heat of evaporation freezes the rest solid, and the molecules that have already turned into a gas will quickly spread out into the vacuum. It doesn't matter how cold the individual molecules of a gas are, they're not going to get any heavier and fall to the ground just because they're cold.

Anne Lyle
01-21-2011, 03:05 AM
I would guess blue as that is what the colour of the hemoglobin deprived of oxygen.

No it's not. Deoxygenated blood is dark red. Veins are blue because of the intervening skin colour. Only molluscs have blue blood:

http://en.wikipedia.org/wiki/Blood#Color

Yes, I know Wikipedia isn't 100% accurate, but trust me - I'm a zoologist.

Astronomer
01-21-2011, 07:49 AM
Anne, thanks for chiming in and contributing your expertise. For my part, I'll just say that I thought we were talking mollusk blood all along. ;)

FOTSGreg
01-21-2011, 08:01 AM
I believe it's going to be red, probably dark red. The haem molecule encloses the oxygen atom that makes it haemoglobin (hemoglobin) in a lattice-like cage. Binding and unbinding is enzymatically controlled. As enzymes have very specific operational temperature ranges and violent interactions don't tend to affect enzymatic reactions overly much, my guess is that the oxygen atoms would remain locked inside the lattice structure and the blood would thus be very dark red (sorry, oxygenated blood is dark red, venous blood is lighter red).