Aliens, for some unknown reason, want all the water (H2O) in our oceans, seas, lakes, rivers, (all large bodies of water on earth), and plan to steal it from us overnight.

Luckily for us, they don't want to wreck life on this planet.

As highly advanced lifeforms, they have the technology to replace all our water with an equivalent amount of "magic liquid". We don't know why they can't make H2O - they just can't, but they can make anything else.

So the question is: Is there a replacement for H2O that the aliens can replace our water with that won't destroy life as we know it? This chemical compound should have most (if not all) of the properties of H2O.

Note: How they manage to do this is irrelevant. You can assume that by some hand-waved process, all the H2O just gets replaced with the aforementioned magic liquid instantaneously.

  • $\begingroup$ And by 'magic liquid', you mean something that actually exists, right? $\endgroup$ – DaaaahWhoosh Jun 3 '15 at 19:16
  • $\begingroup$ Unless you have a simulator that can simulate the properties of a chemical formula you just made up, then yes, I would like to see a formula that currently exists in this world. I will, however, accept a formula that is speculated to work as a substitute as long as sufficient evidence is provided @DaaaahWhoosh $\endgroup$ – anon Jun 3 '15 at 19:19
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    $\begingroup$ I would offer the suggestion of H2O2, since it'll eventually turn into water and oxygen, but I'm wondering if that would still kill all the fish, especially in the deep parts. $\endgroup$ – DaaaahWhoosh Jun 3 '15 at 19:20
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    $\begingroup$ If there exists a liquid that is sufficiently identical to water to not disrupt the very precarious balance of the Earth's ecosystems that can be freely fabricated by the aliens, why don't they just use the fabricated liquid instead of stealing water from an inhabited world? $\endgroup$ – Frostfyre Jun 3 '15 at 19:23
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    $\begingroup$ If this was ever made into a movie, it would be the next Trolls 2. $\endgroup$ – ShemSeger Jun 4 '15 at 2:29

I'll revert to my old pessimistic self and say that there's nothing that can replace good ol' H2O.

Here are some things that a replacement liquid would have to do:

  1. Be denser as a liquid than a solid. This is atypical of most substances, but water is an exception. This is why only the tops of ponds freeze over and the lower layers are frozen. Otherwise, nothing would survive in winter, because ice would form and sink down, letting more water freeze. Ice fishing would be much less interesting nonexistent.
  2. Be the next universal solvent. If you've taken high school biology, then you might have heard the phrase "water is the universal solvent" a couple times. Water is good because it can dissolve quite a lot of things. A related pure-chemistry-inspired property is that water plays a huge role in the reactions of acids and bases.
  3. Stay liquid at room temperature, and the moderate ranges of temperatures seen on Earth. If a substance is solid at 25 degrees Celsius, then we've got a problem (namely, the oceans). It must also be possible for this substance to be gaseous at some point, facilitating the water cycle.
  4. Be useable in both cellular respiration and photosynthesis. The reasons for this are pretty straightforward. These are clearly not the only forms of energy production used by organisms on Earth (e..g thermophiles use different mechanisms), but they're what you'll have to use if you want things to stay normal.
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    $\begingroup$ Dihydrogen monoxide should do the trick. $\endgroup$ – Samuel Jun 3 '15 at 22:30
  • $\begingroup$ Gosh, I totally forgot about Dihydrogen Monoxide! That would be perfect! I'm totally putting that into an answer. $\endgroup$ – ShemSeger Jun 4 '15 at 2:28
  • $\begingroup$ @Samuel, I'm surprised no one suggested DHMO sooner! $\endgroup$ – ShemSeger Jun 4 '15 at 2:48

I believe the answer is "NO". Water is water is water. On top of that, hydrogen and oxygen are two of the most abundant elements in the universe. Stealing it from a populated planet (where you don't want to hurt the lifeforms) is madness.

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    $\begingroup$ I don't see how nitrogen oxide is going to help anyone. $\endgroup$ – DaaaahWhoosh Jun 3 '15 at 19:51
  • $\begingroup$ @DaaaahWhoosh :P~~~ $\endgroup$ – bowlturner Jun 3 '15 at 19:51
  • $\begingroup$ Mad sci-aliens? XD $\endgroup$ – Aify Jun 3 '15 at 20:01
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    $\begingroup$ I've been substituting water with Mountain Dew for years, and so far it seems to work. $\endgroup$ – IchabodE Jun 3 '15 at 21:22
  • $\begingroup$ @MBurke: But Mountain Dew is at least 90% water. $\endgroup$ – jamesqf Jun 3 '15 at 23:10

Since the question specifically wants to use water from Earth (damn, these aliens are insistent), I returned to the drawing board to rethink my approach. My first reaction to this question was to refute it, but I decided to take a look at what substitutes for water were already known and, to my extreme surprise, there is one that is pretty close.

Formamide has demonstrated viability as an alternative solvent to water. It can dissolve most things that dissolve in water. This chemical was originally brought to my attention by this paper, for those who have access to The Journal of Physical Chemistry.

I am leaving this part of the answer here for posterity reasons.

Since these aliens are in dire need of water and (for whatever reason) can only use H2O despite its similarity to an easily fabricated liquid, we, as Earthlings intent on preserving our precious little pearl of a planet, should erect a giant sign in space that says:

$$\large \text{Go to Europa for Water}$$

There are several places in our solar system with water, beyond the Earth. Europa is believed to have more than twice the water volume of Earth's oceans.

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    $\begingroup$ But they want OUR water! $\endgroup$ – Aify Jun 3 '15 at 20:00
  • $\begingroup$ @Aify Why? Our water isn't any more special than water elsewhere in the universe. $\endgroup$ – Frostfyre Jun 3 '15 at 20:15
  • $\begingroup$ Who knows? They're crazy aliens! Maybe for them, it's the last stage of a test of a chemical on life and they need mass test subjects so they're doing it here - the end result should be that life is NOT destroyed. $\endgroup$ – Aify Jun 3 '15 at 20:16
  • $\begingroup$ @Aify See my new paragraphs. $\endgroup$ – Frostfyre Jun 3 '15 at 20:32
  • $\begingroup$ This chemical would be so perfect if only it weren't highly corrosive ._. $\endgroup$ – Aify Jun 3 '15 at 20:34

It is a non-believable old story trope that aliens want our water. Why not just grab a chunk from the Oort cloud? I read reciently that it looks like one of Jupiter's moons appears to have a bit more water than Earth's oceans. The most common elements in the universe are, in order, Hydrogen, Helium, and Oxygen. Water is ubiquitous.

  • $\begingroup$ It's not a handwave, and it's not a non-believable trope. Maybe they already took the water from the Oort cloud and elsewhere, and now have arrived at Earth needing more? Maybe they always need more because any single, scalar quantity is gonna run out sooner or later. You need a rate. Kinda like us and petroleum, isn't it. $\endgroup$ – DrZ214 Jun 10 '15 at 23:57
  • $\begingroup$ As a story, people would see the aliens absconding with the icy moons and hoovering up billions of comets, and hoping and worrying that they will leve Earth alone. $\endgroup$ – JDługosz Jun 11 '15 at 0:53

Dihydrogen Monoxide

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Dihydrogen Monoxide is a clear liquid, mostly flavourless chemical that is often used in pesticide production and distribution which can effectively replace water in an ecosystem. When sprayed over crops it was discovered that DHMO had an almost identical affect on the crops growth as naturally occurring water. Shortly after pure DHMO is introduced into an ecosystem it quickly absorbs minerals in solution making it almost indistinguishable from real water that falls as precipitation!

There are a few ways to detect dihydrogen monoxide however: it is highly reactive with pure sodium, lithium and potassium (as in explosive reactive), and when poured over iron, it can cause a redox reaction that will turn the iron red and make it brittle.

But you can drink it, you can swim in it, and you can even make ice with it! To the naked eye, and without specialized equipment, it would be impossible for the average person to distinguish DHMO from H2O.

You can learn more about DHMO here: Frequently Asked Questions About Dihydrogen Monoxide (DHMO) What is Dihydrogen Monoxide?

  • $\begingroup$ Out-universe comment: Doesn't this could be considered as sarcasm?; in-universe comment: Whoa, people should start to produce it as many as possible as a precaution if aliens do tried to take our water! $\endgroup$ – Hendrik Lie Jun 5 '15 at 20:17