In Isaac Asimov's I, Robot novel, two scientists stationed in an asteroid where mining activities are performed say "We could flood the mines, if this weren't an airless asteroid" when considering possible emergencies they could deliberately trigger.

So the question is: Why couldn't you flood a mine in an asteroid because of its being airless?

Reference info for those who care: the quote is in the chapter "Catch That Rabbit." Here is the context:

"Well, figure it out, yourself. You're the brains you say. Ask yourself some questions. When does DV-5 go out of whack? When did that 'finger' say he did? When a cave-in threatened, or actually occurred, when delicately measured explosives were being laid down, when a difficult seam was hit."

"In other words, during emergencies," Powell was excited.

"Right! When did you expect it to happen! It's the personal initiative factor that's giving us the trouble. And it's just during emergencies in the absence of a human being that personal initiative is most strained. Now what is the logical deduction? How can we create our own stoppage when and where we want it?" He paused triumphantly - he was beginning to enjoy his role - and answered his own question to forestall the obvious answer on Powell's tongue. "By creating our own emergency."

Powell said, "Mike- you're right."

"Thanks, pal. I knew I'd do it some day."

"All right, and skip the sarcasm. We'll save it for Earth, and preserve it in jars for future long, cold winters. Meanwhile, what emergency can we create?"

"We could flood the mines, if this weren't an airless asteroid."

"A witticism, no doubt," said Powell. "Really, Mike, you'll incapacitate me with laughter. What about a mild cave-in?"

Donovan pursed his lips and said, "O.K. by me."

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    $\begingroup$ Because they don't have anything to flood them with in the first place? I think the point isn't "airless" specifically, the point is that there's no resources (like an ocean or a lake or something) they could use at all. $\endgroup$ – Lily Chung Oct 28 '14 at 1:55
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    $\begingroup$ @IstvanChung I agree: probably the intended meaning is "If we were back on earth, we could..." rather than literally "Because we're specifically on this airless asteroid..." $\endgroup$ – David Richerby Oct 28 '14 at 9:35

Because the liquid would boil away.

Boiling is what happens when the partial pressure of a liquid exceeds the ambient pressure. Liquids have higher partial pressure as they get hotter, so we usually associate boiling with high temperature. For example, water needs to be heated to 100°C to boil at 1 atmosphere ambient pressure.

However, pressure is just as much a part of boiling as temperature is. On a asteroid with small gravity, there is essentially no atmosphere, so the ambient pressure is close to 0. Any liquid would boil away.

One issue is that by boiling, the temperature of the remaining liquid would go down, which would cause it to freeze. The process of sublimation (going straight from solid to gaseous form) is much slower, so the solid state of even something like water could persist for a significant time. However, to "flood" a mine in the sense obviously intended in that quote requires liquid. That's going to be quite impractical when it either quickly turns to vapor and escapes, or solid and stops flowing.

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    $\begingroup$ It will not boil away. Only a part of it will boil, the other part will freeze. $\endgroup$ – Anixx Oct 28 '14 at 4:51
  • $\begingroup$ Do you mean boil or evaporate? $\endgroup$ – Burhan Khalid Oct 28 '14 at 6:44
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    $\begingroup$ @Burhan: I'm pretty sure Olin means boil when he writes boil. $\endgroup$ – RedGrittyBrick Oct 28 '14 at 9:11
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    $\begingroup$ @BurhanKhalid Evaporation is the process by which high-energy molecules leave the surface of a liquid. Boiling is the process by which bubbles of gas form within the bulk of the liquid because the vapour pressure exceeds the pressure exerted by the surroundings. On an airless asteroid, there is no air pressure and almost no gravity so the pressure on the liquid is very low and it boils at a low temperature. $\endgroup$ – David Richerby Oct 28 '14 at 9:33
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    $\begingroup$ Flooding would also require gravity, at least if you intended to pour liquid in at the "top" of the mine and have it flow to the "bottom". $\endgroup$ – David Richerby Oct 28 '14 at 9:39

Actually one can flood the mines on an asteroid. The water will become boiling, but before it all boils out the water will freeze.

As such, the scientists could say so only if they anticipated negativity in ice bulbs forming in the mines. But the process of freezing is very slow, so the water most likely would reach the bottom of the mines.

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    $\begingroup$ "Flood" doesn't necessarily mean water. For example, below about -160C, you could try flooding with liquid methane. $\endgroup$ – David Richerby Oct 28 '14 at 9:38
  • $\begingroup$ @DavidRicherby But not in an ambient vacuum. $\endgroup$ – gerrit Oct 28 '14 at 15:15

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