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BigDon
2018-Jan-14, 06:01 PM
Is water ice of the Moon and Mars expected to de-salinate itself like it does on Earth?

Thank you.

Spacedude
2018-Jan-14, 10:24 PM
Hey there Big Don, I'm no moonologist but I'd "guess" that without a water recycling process (rain) that stagnant sources of water/ice might over time absorb the surrounding salts to a saturation point. Mars on the other hand does appear to have "weather" so who knows.

The Backroad Astronomer
2018-Jan-14, 11:00 PM
If the water melted and got filter thru layers of rock it could desalinate that way too, but that is dependent of what types of rocks are under the ice. Also what is in the ice can change the freezing point of the water that could used possibly also.

The Backroad Astronomer
2018-Jan-15, 01:55 AM
Plus water mixed with other substances would lower temperature for freezing so it could be a better substrate for life development.

Squink
2018-Jan-16, 06:03 AM
Even with plain old salty water freezing, lower gravity is going to lower the density gradient, so a block of seawater frozen on the moon probably won't be quite as fresh as one frozen on earth.
Surely someone's done this on the space station, and found little pockets of extra salty ice distributed throughout a frozen globule?
I suppose there might be some sort of weird dendritic transport system that self assembles and transports impurities, but it's hard to believe mere surface tension differences could drive such a complex system very far in the time it takes bulk water to freeze. Still, we've got ice spikes: https://www.physics.utoronto.ca/~smorris/edl/icespikes/icespikes.html xx https://www.youtube.com/watch?v=5RLQ9WMP2Es

kzb
2018-Jan-19, 12:32 PM
Firstly, ice is not going to "melt" on the moon or Mars surface. It sublimes directly into vapour.

So if anything, the sublimation process will concentrate dirt and salts (if there were any to start with) in the ice left behind.

BigDon
2018-Jan-21, 06:38 PM
Firstly, ice is not going to "melt" on the moon or Mars surface. It sublimes directly into vapour.

So if anything, the sublimation process will concentrate dirt and salts (if there were any to start with) in the ice left behind.

Um, I'm talking about when sea water freezes and then freshens over time.

As sea ice ages, its crystals push out some impurities, like dissolved salt.

No liquid phase involved. That's what I'm asking about.

Swift
2018-Jan-21, 10:25 PM
Um, I'm talking about when sea water freezes and then freshens over time.

As sea ice ages, its crystals push out some impurities, like dissolved salt.

No liquid phase involved. That's what I'm asking about.
That doesn't quite make sense to me.

The act of freezing (crystallizing from liquid water to crystalline ice) is a purification process and salt will be "pushed out" from the ice. But I can't think of any mechanism where, once the ice has formed and stays frozen, that there would be further purification.
wikipedia (https://en.wikipedia.org/wiki/Sea_ice#Relationship_to_global_warming_and_climate _change)

Furthermore, sea ice affects the movement of ocean waters. In the freezing process, much of the salt in ocean water is squeezed out of the frozen crystal formations, though some remains frozen in the ice.

Squink
2018-Jan-22, 05:51 AM
That doesn't quite make sense to me.

The act of freezing (crystallizing from liquid water to crystalline ice) is a purification process and salt will be "pushed out" from the ice.
Freezing can be a rather complicated process: https://www.foodingredientsonline.com/doc/frozen-novelties-0001
There's lots of room for different textures, porosities, and regions of varying ion concentration; not necessarily all frozen rock-solid.

Tom Mazanec
2018-Feb-01, 03:33 PM
Firstly, ice is not going to "melt" on the moon or Mars surface. It sublimes directly into vapour.

So if anything, the sublimation process will concentrate dirt and salts (if there were any to start with) in the ice left behind.

Well, IIRC water can exist in liquid form at the bottom of the Hellas Basin...