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Antius

Member

From: Cumbria, UK

Registered: 2007-05-22

Posts: 1,003

CO2 traps on Mars

Interesting article.

http://www.lpi.usra.edu/meetings/geomar … f/7044.pdf

Some extracts:
'The recognition of multiple lines of evidence for low geothermal gradients on Mars leads us inexorably to a planet where exceptional conditions are required to bring liquid water to reasonable drilling depths (e.g. 2 km for a light portable and automated drilling rig). Evidence of very recent volcanic activity should be sought to find intrusive centres less than 10^6 years old whole thermal halo has not decayed away.

At the same time, liquid CO2 is thermodynamically stable in the regolith at much shallower depths and models of Mars regolith must recognise the physical and chemical effects of this. Even if only small quantities are present at any one time, over geological time much of the regolith will have been flushed by liquifers of CO2 with its unusual solvent properties.  The existence of liquid CO2 in the regolith represents an important energetic source of vapour for generating cryovolcanic features [6] and major density flows [7]. It also represents a significant drilling hazard in an environment when conventional drilling mud may be precluded due to cryogenic temperatures and to the expectation of severe losses into porous and brecciated regolith.'

This tends to suggest that the crust of Mars may be riddled with pockets of liquid or solid CO2 within as little as 50m from the surface.  Due to the planets unstable axial tilt, large quantities of CO2 may have migrated underground during ice ages and may remain in impermeable traps to this day.

This could be hazardous to drilling, digging and mining on Mars.  It could also provide an obvious source of power for future colonists.  Liquid CO2 could be withdrawn from liquifers, heated above its critical point using stored solar heat and passed through an open cycle gas turbine.  High pressure gas could also be used to power simple compressed air tools, which would be much easier to fabricate on Mars than electrically powered tools.

The implications for terraforming are obvious – much of the Martian atmosphere may exist as trapped liquid or dry ice underground.  However, if terraforming does begin to increase the average temperature of the planet, trapped CO2 could prove hazardous.  A pocket of liquid CO2 could build pressure until it exceeds the structural strength of the impermeable rock containing it.  It would then release energy explosively.  It may be necessary to seismographically detect these deposits and release the pressure before this can happen.

Last edited by Antius (2017-06-26 07:08:13)

tahanson43206

Moderator

Registered: 2018-04-27

Posts: 19,408

Re: CO2 traps on Mars

This topic has been sitting around without a reply since it was created in 2017.

This post is reserved for an index to posts that may be contributed by NewMars members over time.

I admit chances of contributions are not great... seven years have passed.

The concluding paragraph is very similar to the news from Russia, of methane explosions that blow large sink holes in the landscape.  According to the report I read recently, global warming is allowing water to seep down through the permafrost to pockets of methane.

When pressure builds up it can (and does) heave massive amounts of rock and soil around the site.

(th)

Void

Member

Registered: 2011-12-29

Posts: 7,820

Re: CO2 traps on Mars

It does seem reasonable that much of the Martian atmosphere may be in clathrates in the crust, or dissolved in a mix of water and CO2.

But if Mars has life, I have also considered the possibility of it having snatched much of the Nitrogen in the atmosphere to make Ammonia as an antifreeze.

It has been considered possible that an Ammonia/Water mix could perhaps support alien life at much colder temperatures than what we allow for on Earth.

But likely salts would also be allowed in such a fluid.

There is also speculation on a water/Hydrogen Peroxide mix that can remain liquid at low temperatures.  It is speculated that the dust storms of Mars snow Hydrogen Peroxide.
https://en.wikipedia.org/wiki/Hydrogen_ … %20%C2%B0C.
Quote:

In aqueous solutions, hydrogen peroxide forms a eutectic mixture, exhibiting freezing-point depression down as low as -56 °C; pure water has a freezing point of 0 °C and pure hydrogen peroxide of -0.43 °C.

https://apod.nasa.gov/apod/ap070828.htm … 0on%20Mars.
Quote:

Two planetary scientists recently speculated that were extremophile microbes to involve a mixture of hydrogen peroxide (H2O2) and water (H2O), these microbes might well be able survive the thin, cold, dry atmosphere on Mars.

So, the subsurface of Mars and the liquid they think they have discovered deep down may be something rather weird.

The lake of fluid they think is under the south polar ice cap is made of ????

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Last edited by Void (2024-11-03 21:32:44)

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Calliban

Member

From: Northern England, UK

Registered: 2019-08-18

Posts: 3,793

Re: CO2 traps on Mars

CO2 is far more soluble in water than most other gases, due to the formation of ionic carbonic acid.
https://en.m.wikipedia.org/wiki/Carbonic_acid

Strangely enough, carbonic acid is unstable in the presence of water and decays back into H20 and CO2 quickly.  But the finite halflife of H2CO3 in even a liquid medium results in a high solubility of CO2 at any particular partial pressure.  It is more soluble because it forms covalent bonds with water molecules.

Of course, water on Mars exists as either ice or saturated brines.  Both will be extremely cold, which will extend the half life of H2CO3 and increase CO2 solubility even further.  We know this because colder temperatures mean lower molecular speeds even if carbonic acid decomposition has no minimum activation energy (I don't know if it does or not).  H2CO3 is also denser than water and pure ice, so will tend to sink within solution under gravity.  This explains why deep ocean water is CO2 enriched.

I wonder how this behaviour has played out on Mars over aeons?  Did the formation of carbonic acid result in gradual stripping of the atmosphere as CO2 sank into the porous outer crust?  Will we find pressurised CO2 pockets as we drill into the surface?  Or was the planet's atmosphere sequestered as carbonates deeper within the crust.  It is surely no coincidence that the current atmospheric pressure on Mars is close to vapour pressure of water at its triple point.  A CO2 based atmosphere is unstable on an igneous planet in the presence of liquid water.  This has many implications, both good and bad, for terraforming.

Last edited by Calliban (2024-11-04 15:08:15)

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"Plan and prepare for every possibility, and you will never act. It is nobler to have courage as we stumble into half the things we fear than to analyse every possible obstacle and begin nothing. Great things are achieved by embracing great dangers."

Void

Member

Registered: 2011-12-29

Posts: 7,820

Re: CO2 traps on Mars

Well, for Mars, the relative lack of gravity reduces the forces that may cause ices and fluids to be on top of the crust.

Also, the presumed lack of heat in the crust also reduces the forces that will drive fluids and ices to the surface.
I think part of the reason Mars was habitable earlier on, was that residual heat in the crust tended to melt buried ice and then there would be water eruptions.

I think it is less likely to have eruptions now than in the past.  And it may be that those past eruptions would bring other things like CO2 above the crust.

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A possible method to terraform Mars could be to run electric currents though the crust to melt ice deposits.  This would make those locations unstable to some extent but then water and other fluids might erupt to the surface.

Once you had a lake on the surface, presumably covered in ice and dust, you might microwave that and it may warm the lake bottom and bring heat down to the ice deposites.

There are many big chunks of ice buried even near the equator.

This presumably might be done after you doubled the air pressure on the planet.  Then if the lakes salts were prevalent it could allow a lake of cold brine to resist evaporation, and even so the brine could probably be hit with microwave heat from orbit perhaps.

This might simulate an earlier version of Mars when it had more heat in it's crust.

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Last edited by Void (2024-11-04 15:31:19)

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