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#1 2019-10-28 22:38:59

Rusakov
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Registered: 2012-12-19
Posts: 34

Is terraforming Mars impossible? Maybe not...

There's been the recent hullabaloo about MAVEN data suggesting that terraforming Mars is now an impossibility.

There were two posts on Crowlspace that suggest otherwise, in addition to one "out-there" concept I'll post about as well. I'll post a few bits from the Crowlspace posts first

The newer post: Mars Atmosphere Loss Rates – Truth vs Truism names MAVEN upfront early on in the post:

Collectively several metres of water and perhaps 80 millibars of Carbon Dioxide would be lost over 4.2 billion years – at current rates of loss. As the bare minimum for terraforming is about ~300 millibars of carbon dioxide (equivalent to about 250 millibars of Oxygen) this doesn’t seem like a show stopper for terraforming. If we can supply modern day Mars with ~300 millibars in a few hundred years, then replacing 80 millibars in 4 billion doesn’t seem excessive.

Of course the Sun has changed since its exuberant early days and the total actual loss from Mars is probably somewhere between 2 – 0.5 bars worth of atmosphere and maybe several hundred metres equivalent of water. However the Sun’s output was between 20 – 100 times higher in the very early days of its Main Sequence. This matches the apparent desiccation of Mars about ~3 billion years ago.

The older post: On the (Im)Possibility of Terraforming Mars addresses the "current technology can't terraform Mars" cycle from last year, but might still be of import:

Rather than CO2 to warm the planet indirectly – and not very efficiently – what if we increase the available sunlight?

Present day Mars has about 6 millibars of CO2 in its atmosphere ... if Mars received as much sunlight as Earth, it’d be *too hot* from its CO2 greenhouse effect. If we increased the available sunlight by ~50%, then it should be about right. If we imagine an annular mirror suspended above Mars, directing light down onto the surface ... annular needs at least a Mars sized hole – if it’s close to Mars – and then sufficient width to match 50% the area of Mars. Or about 900 kilometres wide and an average radius of about 4,500 km. Immense, but it doesn’t have to be very heavy.

A “mirror-lens” could be parked at the Mars-Sun L-1 point and use solar radiation pressure to help keep itself in place, directing extra sunlight towards the planet ... the Soletta as such mirrors are called, can be closer to the planet and focus its light into an intense pyrolysis beam to separate oxygen from the metal oxides in the crust directly. No mucking about with plants for millennia required.

a 50 petawatt (i.e. 50,000 trillion watt) beam is sufficient to give Mars an oxygen atmosphere in about 6 years. Mars receives 30 petawatts from the Sun, so our “50% Soletta” gives us 15 petawatts to blast oxygen out of the crust with, taking about 20 years.

Regarding mirrors, an old NextBigFuture post mentioned "tessellation foams" of reflective bubbles that could be "in between the size of Neptune or Saturn" in deep space. So the pyrolysis beam lens wouldn't have an annular mirror at L-1, but could have a much larger tessellation mirror at a different Lagrange point. So a constant beam to the surface might not be viable, but you could still get a lot of oxygen out of the soil.

Of course this assumes that we must solely use space-based infrastructure to achieve successful terraformation. But what if we looked in the opposite direction... underground?

There was a bit in the novel Manifold: Space by Stephen Baxter with a device called a "Paulis mine" used to terraform Earth's Moon - rather than Mars.

The idea is that there's a large amount of volatiles including -not just water- but also nitrogen, various hydrocarbons, etc. But there's a catch: these materials are buried within the mantle, so a very deep hole must be bored out to get to them.

Is this at all realistic? While we can't say for Mars, it's certainly true for Earth. The discovery of naturally occurring ringwoodite from the Earth's mantle suggests that there could be at least as much water in Earth's mantle as there is in its oceans, if not more.

Could something similar hold true for Mars? I'm not an expert at this, but I don't see why not.

So there are still a few cards we might be able to play in regards to terraforming Mars. They might be way out-there, or require a deep dive, but they're plausible nonetheless! wink


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#2 2019-10-29 03:51:26

Terraformer
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Re: Is terraforming Mars impossible? Maybe not...

Martian outgassing exceeds the loss to the solar wind by orders of magnitude, so I'm not worried about atmospheric loss to space.

I don't like space mirrors. They make the planet dependent on a fragile space based infrastructure. I'd prefer to build a worldhouse than a soletta. Or even better, a genetically engineered ecosystem that can thrive at temperatures cold enough to freeze water.


"I guarantee you that at some point, everything's going to go south on you, and you're going to say, 'This is it, this is how I end.' Now you can either accept that, or you can get to work." - Mark Watney

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#3 2019-10-29 04:15:08

louis
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Re: Is terraforming Mars impossible? Maybe not...

Yes - no reason to be downhearted by such a slow rate of atmospheric loss. Even within 500 years I would think we should definitely have the technology to really harness asteroids and make good any loss, but such technology could come a lot sooner than that.

Whether we currently  have the technology to produce trillions of tons of atmosphere (and get the right balance of gases of course!), is quite a different matter. We've never before embarked on such a large engineering project - it would dwarf every other engineering project ever pursued.

I don't rule out solar mirrors, but I wonder why don't build smaller ones closer to the Sun. Does anyone have an idea about how close we can get to the Sun with a solar mirror?


Let's Go to Mars...Google on: Fast Track to Mars blogspot.com

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#4 2019-10-29 10:42:47

Calliban
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From: Northern England, UK
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Re: Is terraforming Mars impossible? Maybe not...

To create a 380mbar pure oxygen atmosphere on Mars; some 1.45E15 tonnes of oxygen would be needed.  This could be created by electrolysing some 1.6E15 tonnes (1.6million cubic kilometres) of water.  Near surface deposits of ice identified on Mars account for 21million cubic km.  So Mars could be terraformed by electrolysing <8% of its detected water reserves.  So creating a breathable atmosphere is achievable in principle.

But the energy requirements are intimidating.  To produce 1.45E15 tonnes of oxygen through electrolysis (even at 100% efficiency) would consume 2.8E25 joules of energy, or 887million GW-years.  That is the equivalent of a million large nuclear reactors, running for 887 years; or all of the sunlight falling onto Mars for 50 years, ignoring any conversion losses.

Basically, to do this in any reasonable human timescale, would take some very big fusion reactors.  And the waste heat would be enough to warm the planet up quite substantially.  We would probably need to use the polar caps as heat sinks and polar water would most likely be our feedstock.  We would probably build a ring of mega reactors around the northern polar cap.

Whilst reactors this size sound enormous, they would probably be on a scale comparable to some of the largest man-made structures on Earth.  With a power density of about 15MW/m3 - a spherical fusion reactor producing 1E15 watts of heat would be ~500m in diameter.  Powerplants this huge would benefit from large scale economies.

Last edited by Calliban (2019-10-29 10:47:36)


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#5 2019-10-29 12:26:17

Terraformer
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Re: Is terraforming Mars impossible? Maybe not...

380mb would be more than twice what is necessary for life, and a crazy fire risk.

Most of the benefits of terraforming come from the first, minimal, steps. Some oxygen in the atmosphere, warmer temperatures, better radiation shielding (including an ozone layer), and the ability to grow food on the surface. A ~100mb mostly CO2 atmosphere is a long way from a 1bar O2/N2 atmosphere.


"I guarantee you that at some point, everything's going to go south on you, and you're going to say, 'This is it, this is how I end.' Now you can either accept that, or you can get to work." - Mark Watney

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#6 2019-10-29 13:44:50

Calliban
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From: Northern England, UK
Registered: 2019-08-18
Posts: 243

Re: Is terraforming Mars impossible? Maybe not...

Terraformer wrote:

380mb would be more than twice what is necessary for life, and a crazy fire risk.

Most of the benefits of terraforming come from the first, minimal, steps. Some oxygen in the atmosphere, warmer temperatures, better radiation shielding (including an ozone layer), and the ability to grow food on the surface. A ~100mb mostly CO2 atmosphere is a long way from a 1bar O2/N2 atmosphere.

Agreed.  If we could build greenhouses that didn't have to be pressurised, the planet would be a lot more habitable.  And with surface doserates lower, habitats would be easier to build.  The question is whether there is enough CO2 on Mars to do that.

If the higher latitudes of Mars could be warmed using orbital mirrors, then ice would sublime.  UV action would dissociate the water vapour into O2 and H2, with the later escaping into space.  I would imagine that this process would be slow.

Last edited by Calliban (2019-10-29 13:48:48)


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#7 2019-10-29 15:08:16

louis
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Re: Is terraforming Mars impossible? Maybe not...

Only slight problem - we can't master fusion yet.

Calliban wrote:

To create a 380mbar pure oxygen atmosphere on Mars; some 1.45E15 tonnes of oxygen would be needed.  This could be created by electrolysing some 1.6E15 tonnes (1.6million cubic kilometres) of water.  Near surface deposits of ice identified on Mars account for 21million cubic km.  So Mars could be terraformed by electrolysing <8% of its detected water reserves.  So creating a breathable atmosphere is achievable in principle.

But the energy requirements are intimidating.  To produce 1.45E15 tonnes of oxygen through electrolysis (even at 100% efficiency) would consume 2.8E25 joules of energy, or 887million GW-years.  That is the equivalent of a million large nuclear reactors, running for 887 years; or all of the sunlight falling onto Mars for 50 years, ignoring any conversion losses.

Basically, to do this in any reasonable human timescale, would take some very big fusion reactors.  And the waste heat would be enough to warm the planet up quite substantially.  We would probably need to use the polar caps as heat sinks and polar water would most likely be our feedstock.  We would probably build a ring of mega reactors around the northern polar cap.

Whilst reactors this size sound enormous, they would probably be on a scale comparable to some of the largest man-made structures on Earth.  With a power density of about 15MW/m3 - a spherical fusion reactor producing 1E15 watts of heat would be ~500m in diameter.  Powerplants this huge would benefit from large scale economies.


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#8 2019-10-29 15:10:55

louis
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Re: Is terraforming Mars impossible? Maybe not...

There was a recent scientific paper that suggested a 3 cm thick covering of transparent aerogel could have a very significant impact in heating up the planet. I did some calculations as regards making enough of that material to cover a large part of the planet...we are talking about billions of tons of material but it's probably still one of the most efficient ways of getting the desired result.


Let's Go to Mars...Google on: Fast Track to Mars blogspot.com

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#9 2019-10-29 15:51:37

Calliban
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From: Northern England, UK
Registered: 2019-08-18
Posts: 243

Re: Is terraforming Mars impossible? Maybe not...

louis wrote:

There was a recent scientific paper that suggested a 3 cm thick covering of transparent aerogel could have a very significant impact in heating up the planet. I did some calculations as regards making enough of that material to cover a large part of the planet...we are talking about billions of tons of material but it's probably still one of the most efficient ways of getting the desired result.

Agreed.  About 4 billion tonnes by my estimate for the whole planet.  Trouble is you can only work with what's there.  If there is only enough CO2 to double or triple atmospheric pressure, then you aren't going to be growing crops under thin polytunnels or building megacities under tents.

Whilst terraforming does not have to imply Earth analogue conditions, it is what we are ideally aiming for.  We won't get there without a lot of energy, time or both.

Last edited by Calliban (2019-10-29 15:53:50)


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#10 2019-10-29 16:22:04

SpaceNut
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Re: Is terraforming Mars impossible? Maybe not...

As mars warms in summer the lose rate accelerates and making the atmospheree thicker with allow for more heat retention which will cause the atmosphere to also accelerate the rate of lose as well. The trick is to slow the lose rate while making the planet warmer.
The next thing is a breathable air mix or its just not going to be worth it.
A glass or polytunnel structure aka dome living is where the retention of air is something that can be done.

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#11 2019-10-29 17:19:40

Calliban
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From: Northern England, UK
Registered: 2019-08-18
Posts: 243

Re: Is terraforming Mars impossible? Maybe not...

"Only slight problem - we can't master fusion yet."

Yes and no.  Fusion can be made to take place in a low cost fusor that you can build in your garden shed and of course fusion yields ample energy in a hydrogen bomb.  But achieving breakeven and ignition in low density plasmas is challenging.

Given the difficulty of achieving magnetic fields stronger than 45T; particle density is limited.  The easiest way of meeting the lawson criterion is to increase confinement time by increasing reactor size.  Hence, the bigger a reactor is, the better its performance.  For fusion, it makes far more sense building terrawatt scale machines than it does building 100MW machines.  For reactors with cores that large, the plasma will begin to extract energy from neutrons as well.

Last edited by Calliban (2019-10-29 17:20:41)


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#12 2019-10-29 19:08:38

SpaceNut
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Re: Is terraforming Mars impossible? Maybe not...

One could create a field on orbit to aid with containment via satelites that could be nuclear powered. Dust the orbit with conductive elements to create a means for the flux lines to build between the satelites.
Duplicate the satelites at higher orbits and cross fields to make a false van radiation belt like effect with the same particle laced lines of flux to act as a barrier.

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#13 2019-11-04 23:09:41

Calliban
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From: Northern England, UK
Registered: 2019-08-18
Posts: 243

Re: Is terraforming Mars impossible? Maybe not...

Economy of scale states that (crudely) for every increase in size of a device, capital cost increases to the 0.6 power.

https://en.m.wikipedia.org/wiki/Economies_of_scale

Let us say we want to build a fusion reactor on Mars that delivers 887million GW-years of energy in 100 years.  That equates to a power of 8.87million GW.  Compared to a 1000MW device, the capital cost would be 14,750 times greater.  The per unit capital cost would be 0.0017 of the 1000MW unit.

There are other factors that favour very large fusion reactors.  The larger the reactor is, the longer the confinement time of particles.  It takes a finite period of time for a particle to cross the containment vessel.  For a given plasma density, the larger the vessel, the more likely an ion is to collide with another ion before reaching the edge.  Finally, there is the cube/square law.  Leakage is a function of surface area, whereas power is a function of volume.  All things considered, it will be much easier to reach the Lawson criterion in a very large reactor.

A Martian civilisation of a sufficient size could build mega reactors to power industry on a scale that is so far unknown on Earth.  Without oceans, Mars is effectively a single huge continent, making it relatively simple to distribute power all over the planet using superconducting cables.  If we assume a Martian population of some 4 billion people, each consuming power at a rate of 10KWe, then a total reactor power of 40,000GW would be needed.  To terraform Mars with a breathable atmosphere in just 100 years by the electrolysis of water; about 100 times more power would be needed.

This amount of heat ejected by the system over this timescale would begin to rival the power of sunlight reaching Mars and would warm it considerably.

In terms of volume: ITER plasma would have a core power density of about 10MW/m3 following plasma ignition.  To produce 8.87million GW implies a plasma volume of 887million cubic metres; or a spherical confinement chamber some 600m in radius.  This sounds achievable, as it amounts to about two-thirds of a mile in diameter.  Extracting heat from the reaction might be difficult at this size range.  Heat loading would amount to nearly 2GW/m2 of the reaction vessel.  Even boiling liquid metal would struggle to remove that much heat.  So a fleet of 100 reactors some 2 orders of magnitude smaller would be more practical.  They would likely be build in a ring around the Martian north pole.

One thing that could be problematic if we attempt to rapidly terraform Mars is structural stability.  The crust of the planet is likely full of water ice and frozen CO2.  If this were to rapidly melt it would probably imperil any structures on the surface.

Last edited by Calliban (2019-11-04 23:29:34)


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#14 2019-11-05 20:50:15

SpaceNut
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Re: Is terraforming Mars impossible? Maybe not...

I have always thought that mars could be made more earth like but its not just about building up a think atmosphere thats breathable, getting liquid water, warming mars, getting the energy source to power it all but one that somehow must increase mass to gain the local gravity to aid in a core thats cold to form a much hotter center to possibly make a megasphere with  radiation belts to help shield the surface.

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#15 2019-11-06 10:10:50

tahanson43206
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Registered: 2018-04-27
Posts: 1,672

Re: Is terraforming Mars impossible? Maybe not...

For SpaceNut re #14 ....

As a reminder, this forum database contains lots of posts about the advantages of working with Venus as compared to the challenges of Mars.

Venus has so many advantages (gravity near 1G, plenty of power because nearer the Sun, etc) that I suspect it will be receiving attention in coming decades.

The key problem to be solved (as I understand it) is to provide a shade to regulate Solar power input to the planet, and the similarity to the need for something like that for Earth make it all the more interesting.

(th)

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