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I was reading up on this question over here:

Could a planet made completely of water exist?

And I was wondering if it would be possible to haul massive amounts of water into space and put it into orbit around a planet. I've seen many videos on the ISS of how water will naturally form a sphere when introduced into zero gravity. I feel like we could introduce water into orbit, then slowly add mass to the orbiting water sphere, potentially creating a new water/ice moon.

Potentially the first water would create an ice ball, but if we continuously added layers to this ice ball, could we theoretically create a new orbital body over time? Perhaps this question could also assume a high orbit, one infeasible for current technology to haul water to, but not for future technology to do.

Are there massive gaps in my thinking, given:

  • A small sphere of 20 meters in diameter.
  • A medium-small sphere at 1 mile in diameter.
  • A medium sphere about 1/100 the size of the moon (21.59 miles).
  • A large sphere, the size of the moon.
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  • $\begingroup$ Hello, Magic Octopus Urn, and welcome to Worldbuilding.SE! Perhaps you could elaborate on the intended size of this orbiting water sphere. That would doubtless be helpful to potential answerers. Please take our tour and visit the help center to learn more about the site. Have a nice day! $\endgroup$
    – Gryphon
    Commented Jul 17, 2018 at 16:42
  • $\begingroup$ @Gryphon updated, with questions about 4 different theoretical sizes. $\endgroup$
    – Magic Octopus Urn
    Commented Jul 17, 2018 at 16:48
  • $\begingroup$ I could have sworn that the minimum size for a water world has already been answered (probably by @HDE 226868) but I can't find it. The closest I could find is this: worldbuilding.stackexchange.com/questions/4969/… $\endgroup$
    – ShadoCat
    Commented Jul 17, 2018 at 17:26
  • $\begingroup$ @ShadoCat that question has been linked (above) since the inception of this question, and was the reason I asked it. $\endgroup$
    – Magic Octopus Urn
    Commented Jul 17, 2018 at 17:33

2 Answers 2

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Your ability to form a water sphere (liquid water) is potentially hamstrung by how quickly you can get the water into place. Water in vacuum (not ice, so if it's already frozen, you've got a chance) will boil before it freezes.

So you won't be able to pump water into vacuum and expect it to form an ice ball. You'll get a rapidly-expanding cloud of frozen steam as the boiling water expands to fill all available space (that is to say, the immediate vicinity).

I'd need some equations I don't currently have access to in order to determine the rate at which you'd have to pour water into the void that its gravity would overcome the outward trajectory imparted by the boiling action, but it's safe to say that unless you can conjure up your asteroid-sized water blob instantaneously (or contain the water until it freezes) you're not going to be able to build a snowman... er... new orbital body.

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  • $\begingroup$ Interesting, would it boil in the absence of direct sunlight; or the opposite-- flash freeze before it can become a sphere? I suppose my thought process was seriously hung up on the fact that the ISS has an artificial atmosphere in zero gravity-- I momentarily forgot about that. Maybe if you could maintain the liquid form of water (a pseudo atmosphere assumed or something) this would be feasible. $\endgroup$
    – Magic Octopus Urn
    Commented Jul 17, 2018 at 17:25
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    $\begingroup$ @MagicOctopusUrn The boiling point of any fluid drops as the external pressure goes down; as there would be no pressure on the water in the vacuum of space it's boiling point would be very low so it will in fact boil while below it's normal freezing point. $\endgroup$
    – Ash
    Commented Jul 17, 2018 at 17:31
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    $\begingroup$ Ahh... my word I need to brush up on the one 101 physics course I took. It does make sense now that I remembered the spherical shape of the water is due to a zero-gravity well inside of an atmosphere. It isn't dispersing to a lower pressure area because the other areas aren't devoid of pressure in the ISS. In space, it would try to disperse immediately, gotcha. $\endgroup$
    – Magic Octopus Urn
    Commented Jul 17, 2018 at 17:37
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    $\begingroup$ Would it be possible to construct it out of ice initially, then melt it once it is massive enough to hold itself together under its own gravity? Perhaps build further out in the solar system where it wouldn't melt or sublimate too quickly, then move it to the inner solar system where the sun can melt it? $\endgroup$
    – TheBlackCat
    Commented Jul 17, 2018 at 21:51
  • $\begingroup$ @MagicOctopusUrn - minor point of contention: nothing in the ISS is in a zero-gravity "well". Pretty much everything in the ISS is experiencing most of 1G - it's not far enough from Earth (let alone the sun) not to be within the planets' gravity well. Nothing in the solar system, for that matter, is outside the sun's gravity well. They're just falling towards the thing they're orbiting (Earth, the Sun, etc.) and missing. $\endgroup$
    – jdunlop
    Commented Jul 17, 2018 at 22:52
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The ball will surely dissappear (unless it´s really big)

Your water will evaporate as soon as it is deployed into space. Remember the water you see inside the Space Station is inside an atmosphere (not in the void of space), and there is air pressure around the water. So it mantains its "bubbly" shape. In the emptiness of the space there is no air pressure, so water instantly boils. Unless...

If you deploy an ice ball in the Earth shade (in the orbit side away from the sun) you could have cold enough to let the ice ball maintain the shape. But as soon as it orbits towards the light side, it will start to evaporate, and you will have a very nice comet going through. If your ball has not evaporated completely when it arrives again to the dark side of the orbit, it will again freeze. But soon or later it will dissappear.

Perhaps if you have a water ball bigger than the size of the moon (and I say "perhaps". I am not good at planetary maths), it could generate enough gravity to retain the evaporated water, and create an "atmosphere". So instead of just a big water drop, you may end up having a "waterworld".

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  • $\begingroup$ The last paragraph is the goal/thought, pointing out the ISS has an atmosphere makes me feel stupid. Can't believe I overlooked that. Thank you. $\endgroup$
    – Magic Octopus Urn
    Commented Jul 17, 2018 at 17:26
  • $\begingroup$ I don't think doing it in the shade will be enough. The zero pressure in space would boil it all off anyway $\endgroup$
    – ifly6
    Commented Jul 19, 2018 at 19:36

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