Beautiful emerald-green ice
- Thread starter DjVortex
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Pure water ice is naturally colourless. It looks blue under certain circumstances for much the same reason that the sky is blue - in other words, it's a physical property, not a chemical property, and the same physics would apply to different chemical substances with similar physical properties. So, most "ice" is either blue, or colourless.
Most other things that qualify as "ice" (eg. carbon dioxide, methane, ammonia, oxygen, nitrogen, hydrogen) are likewise colourless, which is why most iceworlds are rather drab, grey affairs. The only other prominent colour that occurs on known real-universe iceworlds like Pluto is pink, which comes from reddish-brown contaminants in the ice. Specifically, tholins, which form spontaneously when UV light strikes methane gas. Tholins are the reason the clouds of the gas giants and the atmosphere of the moon Titan are reddish.
Is there some physical process that could generate real-world green ice on planets? Sure, but it's kind of improbable. For example, suppose you have a lot of nickel dissolved in water, which then freezes. Hey presto, a giant green iceblock. The first trick is to get that "green water" in the first place, since a lot of other things are both more soluble and more abundant than nickel, which will change the apparent colour. Iron, for example, which would make the water reddish-brown instead of green, and on most worlds that are nickel-rich, there's plenty of iron around as well; a nickel-rich, iron-poor planet would be rare indeed. Chromium would make "green water" too (chromium contaminants are what make actual emeralds green in colour), but chromium is even rarer than nickel.
The second trick would be the "freezing the water" thing, because you don't get green ice just by sprinkling solid nickel compounds onto solid ice; the ice needs to be liquid. So you need a world that was once liquid but later froze, or a world that's not solid ice all the time (like in a highly eccentric, cometary orbit), so it regularly melts and refreezes.
Of course, the other thing in the universe that's green is chlorophyll-based life. A thin green scum growing on or just under the surface of an ice world is entirely possible to develop, if the world has been infected with extremophile algae. You might also get algae-based green ice if you take a "primordial soup" planet full of primitive life, and suddenly freeze it; the algae will all be dead but the chlorophyll will be snap-frozen and won't have degraded from its green colour.
Most other things that qualify as "ice" (eg. carbon dioxide, methane, ammonia, oxygen, nitrogen, hydrogen) are likewise colourless, which is why most iceworlds are rather drab, grey affairs. The only other prominent colour that occurs on known real-universe iceworlds like Pluto is pink, which comes from reddish-brown contaminants in the ice. Specifically, tholins, which form spontaneously when UV light strikes methane gas. Tholins are the reason the clouds of the gas giants and the atmosphere of the moon Titan are reddish.
Is there some physical process that could generate real-world green ice on planets? Sure, but it's kind of improbable. For example, suppose you have a lot of nickel dissolved in water, which then freezes. Hey presto, a giant green iceblock. The first trick is to get that "green water" in the first place, since a lot of other things are both more soluble and more abundant than nickel, which will change the apparent colour. Iron, for example, which would make the water reddish-brown instead of green, and on most worlds that are nickel-rich, there's plenty of iron around as well; a nickel-rich, iron-poor planet would be rare indeed. Chromium would make "green water" too (chromium contaminants are what make actual emeralds green in colour), but chromium is even rarer than nickel.
The second trick would be the "freezing the water" thing, because you don't get green ice just by sprinkling solid nickel compounds onto solid ice; the ice needs to be liquid. So you need a world that was once liquid but later froze, or a world that's not solid ice all the time (like in a highly eccentric, cometary orbit), so it regularly melts and refreezes.
Of course, the other thing in the universe that's green is chlorophyll-based life. A thin green scum growing on or just under the surface of an ice world is entirely possible to develop, if the world has been infected with extremophile algae. You might also get algae-based green ice if you take a "primordial soup" planet full of primitive life, and suddenly freeze it; the algae will all be dead but the chlorophyll will be snap-frozen and won't have degraded from its green colour.
Green Ice National Geographic
What about brown/black? 
Looks green & purple to me.
Indeed, there may not be natural green ice, but green is mixing blue and yellow
Might be. I'm not really good in colours.Looks green & purple to me.
I vividly remember a night out to dinner on vacation with my father and family. The service had been particularly bad and unrepentant. Dad wrote the above phrase in the "Tip" blank on the check.
My mother was not amused.
On earth ice can appear green based on what is in the water. I remember skating on green ice pond when I was young. If the ice was clear you could see the green algae covered rocky bottom. Not technically green ice but it looks green.
If there is lots of green biological stuff under the ice it can appear green.
Not my picture, its from internet. But illustrates the point.
If there is lots of green biological stuff under the ice it can appear green.
Not my picture, its from internet. But illustrates the point.