Author Topic: Utopia Planitia 'utopia' for ice  (Read 6409 times)

Offline lamontagne

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Re: Utopia Planitia 'utopia' for ice
« Reply #20 on: 11/24/2016 02:29 AM »
Why are we expecting perchlorates in mars ice?  My understanding was that perchlorates were due to ultraviolet influence on a practically anhydrous cold Mars. I.E. that they were geologically recent.

Freezing ice, as any crystal, excludes unwanted ions from its structure.  Glacier ice, although formed in sea water, is freshwater.  Why should this be different on Mars?  There may well be salt layers over ice sheets, or ice sheets with intermediate salt and dust, and recent layers of ice may have trapped perchlorates in the sand between the layers, but shouldn't ancient ice be clean, since it predates the perchlorates?


Online guckyfan

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Re: Utopia Planitia 'utopia' for ice
« Reply #21 on: 11/24/2016 04:26 AM »
Why are we expecting perchlorates in mars ice?  My understanding was that perchlorates were due to ultraviolet influence on a practically anhydrous cold Mars. I.E. that they were geologically recent.

In these discussions the most negative assumptions are always expressed. If someone has a different opinion he is just handwaving the problems away.

But assuming that perchlorates have formed on the surface for a long time they would have been transported with dust over the fresh precipitation. So there might be some level of perchlorates in them. I really don't expect the deposits to be brines. The salinity would be very likely low, maybe very low.

Offline RonM

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Re: Utopia Planitia 'utopia' for ice
« Reply #22 on: 11/24/2016 04:41 AM »
Why are we expecting perchlorates in mars ice?  My understanding was that perchlorates were due to ultraviolet influence on a practically anhydrous cold Mars. I.E. that they were geologically recent.

In these discussions the most negative assumptions are always expressed. If someone has a different opinion he is just handwaving the problems away.

But assuming that perchlorates have formed on the surface for a long time they would have been transported with dust over the fresh precipitation. So there might be some level of perchlorates in them. I really don't expect the deposits to be brines. The salinity would be very likely low, maybe very low.

The only way to be sure is to test the ice. Whichever site SpaceX selects, they need to send a Red Dragon that can test the ice.

Offline Rei

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Re: Utopia Planitia 'utopia' for ice
« Reply #23 on: 11/24/2016 12:17 PM »
Why are we expecting perchlorates in mars ice?  My understanding was that perchlorates were due to ultraviolet influence on a practically anhydrous cold Mars. I.E. that they were geologically recent.

Freezing ice, as any crystal, excludes unwanted ions from its structure.  Glacier ice, although formed in sea water, is freshwater.  Why should this be different on Mars?  There may well be salt layers over ice sheets, or ice sheets with intermediate salt and dust, and recent layers of ice may have trapped perchlorates in the sand between the layers, but shouldn't ancient ice be clean, since it predates the perchlorates?

From the National Snow and Ice Datacenter:

Quote
Can you drink melted sea ice?

New ice is usually very salty because it contains concentrated droplets called brine that are trapped in pockets between the ice crystals, and so it would not make good drinking water. As ice ages, the brine eventually drains through the ice, and by the time it becomes multiyear ice, nearly all of the brine is gone.

Unless you think that the brine has been able to drain out (to where?), the salt would still be there.  Any sublimation would be expected to concentrate salts near the surface as well.

As for contaminants, first, re: perchlorates: unless the ice deposit is older than 3BY, the background atmosphere would be similar to today's, and subject to the same perchlorate-forming processes.  Even if it's older, perchlorate salts are highly hygroscopic and can sometimes form flowing liquids even on the surface.

But perchlorates aren't the only contaminant on Mars. One for example that gets little discussion is hexavalent chromium.  Lacking an oxygen-rich atmosphere, a relevant fraction of the chromium in Martian dust appears to be in a hexavalent state.  Unless Mars previously had an oxygen-rich atmosphere, the same would be expected to be the case.  Hexavalent chromium is an exceedingly potent mutagen and carcinogen, most notable in its ability to contaminate groundwater. 

There are also other contaminants - for example, arsenic appears to be more common in Martian dusts than on Earth.
« Last Edit: 11/24/2016 12:18 PM by Rei »

Online guckyfan

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Re: Utopia Planitia 'utopia' for ice
« Reply #24 on: 11/24/2016 02:35 PM »
Without reading it again, I am sure it was said the ice is from precipitation. That's why it is mixed with dust. So no brine from an early ocean. Whatever impurities are there, they would come from the dust.

Offline lamontagne

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Re: Utopia Planitia 'utopia' for ice
« Reply #25 on: 11/24/2016 06:38 PM »
Why are we expecting perchlorates in mars ice?  My understanding was that perchlorates were due to ultraviolet influence on a practically anhydrous cold Mars. I.E. that they were geologically recent.

Freezing ice, as any crystal, excludes unwanted ions from its structure.  Glacier ice, although formed in sea water, is freshwater.  Why should this be different on Mars?  There may well be salt layers over ice sheets, or ice sheets with intermediate salt and dust, and recent layers of ice may have trapped perchlorates in the sand between the layers, but shouldn't ancient ice be clean, since it predates the perchlorates?


From the National Snow and Ice Datacenter:

Quote
Can you drink melted sea ice?

New ice is usually very salty because it contains concentrated droplets called brine that are trapped in pockets between the ice crystals, and so it would not make good drinking water. As ice ages, the brine eventually drains through the ice, and by the time it becomes multiyear ice, nearly all of the brine is gone.

Unless you think that the brine has been able to drain out (to where?), the salt would still be there.  Any sublimation would be expected to concentrate salts near the surface as well.

As for contaminants, first, re: perchlorates: unless the ice deposit is older than 3BY, the background atmosphere would be similar to today's, and subject to the same perchlorate-forming processes.  Even if it's older, perchlorate salts are highly hygroscopic and can sometimes form flowing liquids even on the surface.

But perchlorates aren't the only contaminant on Mars. One for example that gets little discussion is hexavalent chromium.  Lacking an oxygen-rich atmosphere, a relevant fraction of the chromium in Martian dust appears to be in a hexavalent state.  Unless Mars previously had an oxygen-rich atmosphere, the same would be expected to be the case.  Hexavalent chromium is an exceedingly potent mutagen and carcinogen, most notable in its ability to contaminate groundwater. 

There are also other contaminants - for example, arsenic appears to be more common in Martian dusts than on Earth.

According to the article, the water is probably from later precipitation, a kind of local ice sheet, and not 'ancient' water, as I though.  As precipitation though, there might not be any brine, but alternatively there might be other stuff brought in with the dust.  And if the water precipitated onto an existing salt layer, there might well be brine in the mix.
I admit I was completely wrong about sea ice, it clearly freezes with brine in it.  I guess it freezes around unfrozen brine pockets (since these have a lower freezing point) and these drain out by more or less melting their way down, but pretty obviously not bellow the level the ice is floating in the sea.  Would sea ice drain out and get less dense, floating in a brinier and brinier oceans?  I guess this must happen in costal areas in Northern countries, wonder what are the results, when isolated bays freeze?

Briny oceans clearly diffuse into permafrost, so I guess I'll start siding with the people that think the ice may be pretty salty and dirty...

I join a nice text on salt in permafrost, that blew away most of my hopes for clean ice...


Offline Russel

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Re: Utopia Planitia 'utopia' for ice
« Reply #26 on: 11/25/2016 09:40 AM »
Some basic questions.

Where is this location? How far from the equator?

How deep do you have to dig (overburden) before you get to ice? And through what?

How far is it from somewhere you'd actually want to land/explore?

Offline redliox

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Re: Utopia Planitia 'utopia' for ice
« Reply #27 on: 11/25/2016 11:13 AM »
Some basic questions.

Where is this location? How far from the equator?

How deep do you have to dig (overburden) before you get to ice? And through what?

How far is it from somewhere you'd actually want to land/explore?

I'll answer.

1) It's about 40 degrees North and 75 to 90 degrees East. I checked Martian maps and this was the discovery's aprox area.
2) An estimate between 3 to 33 feet was given; if the former that's reasonable for a startup base to dig to.
3) Painfully far.  It's Mars' equivalence of the Dakotas, as in middle of flat broad and featureless plains. Viking 2 landed a ways East in Utopia's vaguely more interesting area.  As I said before, it is tens to hundreds of km away from much.
"Let the trails lead where they may, I will follow."
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