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Would it be possible for an earth-like planet to have a lake made of liquid gallium?

I assume that the lake would probably have to be near the equator to avoid having it freeze over frequently. Evaporation wouldn't be a problem due to gallium's high boiling point.

Would the bottom of the lake have to be made of any certain substance for this to work? What sort of effects would it have?

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    $\begingroup$ it's 6 times heavier than water so when it rains pools of water of it will collect on it and then possibly freeze the surface (which will then keep floating) $\endgroup$ – ratchet freak Oct 11 '14 at 17:38
  • $\begingroup$ "it's 6 times heavier than water so when it rains..." - incorrectly assumed the gallium would be "raining" and was thinking along the lines of "... car repair shops make a killing in rain repairs." $\endgroup$ – DoubleDouble Dec 21 '15 at 18:59
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As cool as it may sound, probably not.

First of all, I'm not sure where so much gallium would come from.

Secondly, there can't be a "gallium cycle" in the way that there is a water cycle, because gallium boils at 2400 C (despite its low melting point of 30 C). If you don't have a gallium cycle, what replenishes the gallium in the lake? It will seep away, get carried away by weather, leaks, animals, plants... It could be on some impermeable layer of granite in the middle of a barren wasteland as @Tigt suggests. It could remain fairly intact if underground.

There are gallium alloys with different melting/boiling points. Galinstan, an alloy of gallium, indium, and tin, melts at -19 C and boils at over 1300 C.

There are also similar substances - an alloy of sodium and potassium is liquid between -12.6 C and 785 C, but will react violently with many things.

Caesium melts at 28.5 C and boils at 671 C, but is extremely reactive.

If you want lakes of any liquid metal, your best bet is mercury, which melts at -39 C and boils at 357 C, enough to give off (very toxic) vapours at room temperature. This is quite close to water's 100 C, so I can imagine the water cycle being replaced by a mercury cycle on a not-so-Earthlike planet.

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    $\begingroup$ Yeah, but mercury is toxic - which is the whole reason I wanted to use gallium. $\endgroup$ – Epiglottal Axolotl Oct 11 '14 at 19:41
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    $\begingroup$ unless you have organisms that are not effected by mercury poisoning (or even need it to live) but that is a different question $\endgroup$ – ratchet freak Oct 11 '14 at 19:56
  • $\begingroup$ So if the bottom of the lake was impermeable enough it would work? $\endgroup$ – Epiglottal Axolotl Oct 11 '14 at 22:07
  • $\begingroup$ If the lake has some way of having its gallium naturally replenished or is very young (having been created by some one-time event), it could work. $\endgroup$ – Kevin Oct 12 '14 at 4:36
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    $\begingroup$ @Stendika Only if the lake is young as Kevin said, or was only recently (eg in an earthquake) opened up, having previously been underground. It can't survive in one place for very long if it's on the surface: for example, if a storm came to the area, some of the gallium could be washed out; and, if it's next to a volcanic lake, then there will also be earthquakes. And as EricMoore said, it would oxidise into a solid oxide $\endgroup$ – user329 Oct 12 '14 at 6:45
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With the bottom of the lake, it's less important to make it impenetrable and more that the lake is constantly fed; liquids get into everything, eventually, so it may be sufficient to have the bottom be granite or other serious stones without too much drainage. (Let's hope they're not above any aquifers.)

That also raises the question of where in fact does this draining gallium go; caves, mines, underwater lake systems?

As for what feeds the gallium lakes, that's probably more up to you than any speculation I could offer.

As far as the freezing goes, you might be able to embrace it; life does exist under frozen pond & lake surfaces, if something is going to be swimming in the gallium. If it's purely for effect to have shiny roiling lakes, you could consider geological activity that keeps things piping hot (and could also help explain the gallium source, if it recycles the draining stuff or whatever). Nearer the equator, cooling effects like weather could be shrugged off if the lakes aren't still; waves do a fair job of stirring things up.

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In addition to the concerns about it leaking out, gallium is a relatively reactive metal. The (solid) metal is relatively resistant to oxidation because it tends to produce a layer of dense oxide that limits further corrosion. A lake exposed to the elements would see a lot more mixing, and couldn't maintain a stable oxide layer. Each raindrop would probably disturb the surface enough to allow some further oxidation. Wind would also expose surfaces, etc. Even if it didn't leak out, it'd oxidize away in (I'm guessing here) a few years.

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  • $\begingroup$ Welcome to our site! Thanks for answering! If you added links or math to support your statements, you'd see more upvotes and get more rep! $\endgroup$ – PipperChip Oct 13 '14 at 17:38

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