Areoforming Mercury

Terraformer · 2013-10-03 08:43:31

Mercury is, as everyone here will know, has a magnetosphere but no atmosphere. It also has, it seems, large deposits of water ice at the poles, which I suspect probably have a lot to do with it's magnetic field and proximity to the sun.

Josh suggested earlier that a small Lunar atmosphere could be baked out of the surface using mirrors. Mercury, of course, is a lot closer to the sun and has a higher surface gravity, so getting a given atmospheric pressure will be significantly easier, probably by about an order of magnitude.

Unfortunately, the Mercurian exosphere will be very, very hot, due to it being composed predominantly of oxygen. Injecting carbon dust into the atmosphere to form CO2 may help, as it would serve as a very good emitter of infrared - and at such low pressures, may act more as an antigreenhouse gas than a greenhouse gas. The magnetic field may also help in retaining the atmosphere.

Why do this? Well, I haven't quite figured that out, except that I prefer to build worldhouses with some atmosphere above them.

RobertDyck · 2013-10-03 09:54:49

According to the website www.solarviews.org Mercury has surface gravity of 2.78 m/s^2, while Mars has 3.72 m/^2, and Earth has 9.78 m/s^2. That means Mercury has 28.4% that of Earth, while Mars has 38.0% that of Earth.

As for terraforming Mercury: why? Mercury is the best mining world you could hope for. Low gravity means high proportion of metal at the surface, and average planetary density is higher than the Earth. Mean density is 5.42 g/cm^3 while Earth is 5.515 g/cm^3. That means lots of metal. And rotation has a 3:2 resonnance with its orbit, which gives it a solar day 176 Earth days long. That's 88 days of sunlight followed by 88 days of night. That means billions of years of extreme surface heat, followed by extreme cold. That will have concentrated any metals that can be melted in that heat, so expect viens on the surface. Great for mining.

It's extremely close to the Sun, so lots of solar enery. You wouldn't use photovoltaic panels, because most we know how to make would melt. But it would be perfect for a sterling engine. Use a parabolic mirror to focus sunlight at one end for heat, and a shade the other end with a radiator exposed to the cold of space. Since Mercury has vacuum, anything in shade but exposed to the sky will be as cold as space.

Use the heat of the Sun, perhaps concentrated with another parabolic mirror, to smelt metal. Unlimited free heat. A mining operation could have 2 mine sites on opposite sides of the planet. Mine one for 88 days, then everyone goes to the other.

Habitat would HAVE to be underground. Solar radiation would be extreme. Digging underground should be easy for a mining operation.

Why spoil this with an atmosphere?

Midoshi · 2013-10-03 10:26:06

Just a minor correction, RobertDyck: That figure of 2.78 m/s^2 for Mercury's surface gravity is inaccurate. In fact it is 3.70 m/s^2, almost identical to Mars. You can confirm this by plugging the mass and radius of Mercury into Newton's law of gravitation, or check this list of Mercurial facts & figures from NASA. Due to the way the math works out, Mercury still has a significantly smaller escape velocity than Mars (4.25 km/s vs 5.03 km/s), so your argument still has merit.

RobertDyck · 2013-10-03 16:29:17

Amazing how data changes. Data from a JPL website from 2001 said Mercury had a density of 5.90 g/cm^2. And higher mass, and higher surface gravity. But Messenger is in orbit now, so collecting more precise data.

I sent an email to the Messenger team when it first entered orbit. I asked about gallium and indium; elements necessary for an extremely highly efficient photovoltaic cell, but rare on Earth. Those metals melt at temperatures Mercury experiences during daylight, but their mineral ore may not. A mine would use a sterling engine, but export the metals to Earth. Unfortunately the response was their instruments are not designed to detect them. Oh well.

Terraformer · 2013-10-04 06:43:06

Well, actually, I was thinking about this as the first step towards a worldhouse for Mercury. I'm very wary of a worldhouse where small pebbles can cause major damage, and it has to be constantly watched to make sure it doesn't fail.

JoshNH4H · 2013-10-06 20:32:15

I think the convention in discussions of terraforming is to speak more of the "How" than the "Why", because we're so far removed from a species that would terraform that we can't really understand the economic justification for doing so. This is the optimist's way of saying that terraforming would be extremely expensive and would have only small benefits monetarily, and completely unknown but probably not that significant benefits when it comes to human happiness (How long are we humans gonna be around in such an inefficient, non-resilient, and low-uptime form, anyway?).

Having said that, the how is a lot simpler to address. To get oxygen from the rocks en masse, you have to heat them up to plasma temperatures, and leave them there long enough for the lighter oxygen to scatter away faster than the heavier metals. As a factor-of-two estimate, let's say 60 MJ/kg of Oxygen, including all loss factors from the moment the light hits the mirror.

You said aeroforming. Let's say that means .5 kPa. Over the entire surface of Mercury, that corresponds to 1e16 kg of Oxygen. This equates to 6e23 Joules. Given the solar constant at Mercury of 9120 W/m^2, one needs to install a mirror capacity of 2.1e12 m^2*yr. That is to say, to do it in one year, you need 2.1e12 m^2. To do it in 100, you need 2.1e10 m^2.

Let's say you want to do it in 21 years. This necessitates 1e11 m^2 of mirrors. That's a square array 316 km on a side, or circular with a radius of 178 km.

And yes, this time I did check to make sure that I wasn't off by six orders of magnitude. Feel free to check, and in fact I encourage you to do so. Note that I have said nothing of mirror geometries or structure, or in fact exactly how you get the material to heat up past its vaporization point thus far.

Now, with regards to those questions which I haven't answered: The only way I can think to do so would be to turn the heat up so rapidly that intense pressures as well as inertia keep the stuff solid up to insane temperatures. To be especially clear, I'm not sure if this would work or not.

If it does work, a mirror that's 316 km per side seems quite achievable. That's big (It's approximately the distance between Washington, DC, and New York City) but not insanely so. If we're talking about building a worldhouse it's a much smaller effort.

In terms of making the process work, I would imagine that spreading carbon dust would be helpful. It's also possible that if the process is done at a large enough scale, the plasma produced would be optically thick enough that it would absorb a significant amount of light and thus continue to heat up.

[For the pessimists among us: Even if you assume that you need 250 MJ/kg of Oxygen, the mirror's per-side length only increases to 645 km, which is a bit more than the distance between LA and San Francisco, or for the Robert's sake, a bit less than the distance from Toronto to Quebec City.]

RobertDyck · 2013-10-06 21:10:30

Actually, Mercury could be the model for planets in other solar systems. Our Sun is a medium size star, but there are far more small stars. They're something like 10 times as many small stars as medium, and 10 times as many medium as large, and 10 times as many large as extra-large. Depending on your definition of small, medium, and large; but you get the idea. There are far more red dwarf stars in our galaxy. I saw one documentary that quoted a astrophysicist who had calculated the maximum number of gas giants. His calculation said for a star the size of our Sun, we have the maximum number. He said if our solar system had any more, then gravity would have ejected the extra one. He said that may have happened. He also said giants must space themselves with a mathematical distance, if they start too close they'll drift apart. And if they do, gravity from the outer most will "push" Kuiper Belt objects. The object would move into elliptical orbits, and inclined from the ecliptic. Looking at our solar system, that's exactly the orbit Pluto is in. So Pluto is a Kuiper Belt object that has been pushed as Neptune moved farther out. This is evidence that Neptune started closer, then moved. And composition of Saturn and Neptune hint they may have traded places. That isn't conclusive yet, but that much movement leaves the possibility that we did have another gas giant, and it was ejected.

I mention this because smaller stars have a smaller number of planets. And red dwarf stars are cooler, with a terrestrial ecozone closer in. So close that they will experience tides from the star, similar to Mercury. That tidal force could create a magnetic field, just like Mercury. The magnetic field could protect an atmosphere. But tides from a star could cause rotational resonance similar to Mercury. So talking about terraforming Mercury could be preparation for settling planets around other stars.

JoshNH4H · 2013-10-07 10:51:03

In a related finding, I've heard that the sheer size of Jupiter somehow implies that there should be an ejected gas giant out there somewhere. I don't know the reasoning or even if that was the same finding as the one you were describing, but if it isn't it's a cool convergence. An article on the topic can be found here. It's quite interesting. And while I question your line of reasoning, I don't doubt that (If we're still a planet-based civilization by the time we get to other star systems, which seems unlikely) we'll end up on terrestrial planets in close orbits around red dwarf stars. More likely we'll jump from system to system on ejected bodies in interstellar space, with major population centers at ejected gas giants, and smaller ones on ejected terrestrial planets or planetoids.

Antius · 2013-10-07 11:48:11

World houses work much better if they can be constructed incrementally - i.e. you start by digging out a modest sized cave 30 metres beneath the surface and filling it with breathable air, a city and population, etc. As population pressures increase, you dig another cave, and then another and so on. Ultimately, after several centuries of expansion, a large fraction of the planet would be tunnelled out and an interconnected biosphere will have developed. Engineers will become more adventurous, developing larger and larger caverns, until ultimately you have a world house.

If you look at the way we have built things on Earth, we rarely start with the ambition of building a metropolis. Towns, roads, agriculture, etc, have always started small and grown bigger incrementally. This is the way other planets will ultimately be colonised and terraformed.

karov · 2013-10-07 13:30:08

In fact (!) Mercury is fairly easy to terraform.
It is a myth that it is "too close" to the Sun to be possible, or that a airless world is "more convenient for mining"...

1. David Semloh's way -- Type "David Semloh Mercury" in Google Discussions and read.
https://www.google.bg/search?q=David+Se … ry&tbm=dsc

2. Hall's weather machine -- http://www.acceleratingfuture.com/peopl … r-machine/ -- instead of giant mirrors in orbit or as statites, the zillions of aerostat bubble mirrors could achieve the same if not better effect. AFAIR giants like Freeman Dyson and Paul Birch showed that using optics ( Archimedes age tech! ) one could collect enough light to illuminate to Earth level a planet up to several light years away (!) ORRR , to fend a planet of light down to Earth level on a distance as close as several solar radii from the Sun. With the 2nd or 3rd or higher generation of http://en.wikipedia.org/wiki/J._Storrs_Hall 's "weather machine" ( WM ) - each and every square milimeter of Mercury's surface'es illumination will be regulated with enormous precision. The actual axial rotation cycle won't matter anywhere cause the sky and all the lights and darknesses on it would be just images of a giant hologram. The excess light the global weather machine would beam where necessary, turning the so terraformed Mercury into a giant laser... The WM could maintain and regulate planetary magfield, to provide veeery deep tropopause cold trap, or to keep actual exobase temperatures into the real several K cryo-range. The powers of WM scheme are so huge, that the things get a little bit dull = does not matter what underbody one is working with, a paradise Earth-like conditions are easy. WM-ed planet is equivalent to worldhoused planet / planemo / but with a foamy tent, each foamlet = living cell, WM of higher gens = smart, adaptive, multi-cellular organisms.

BTW, for our Mercury gen#1 WM is enough.

gen#2 or higher for planets almost dipping into their suns like: http://www.space.com/22451-fastest-eart … er78b.html OR http://news.yahoo.com/strange-lava-plan … 51621.html

100-1000km wide mirror foamlets could orbit or statite in vacuum, too.

3. ...

4. ...

RobertDyck · 2013-10-07 20:17:11

Remember, I keep quoting from this book: "Rare Earth: Why Complex Life is Uncommon in the Universe"
I purchased a copy when it was on the Mars Society store book list.

The basic premise is Earth has a large moon. That causes tides not only in the ocean, but in the crust. That slows Earth's rotation, but only slows the Earth, not the inner core. The mantle is hot and plastic, but physically connected to the crust. The liquid core separates the inner core, so tides do not slow the inner core. This creates a differential between rotation rate of the inner core vs the rest of the planet. That differential rotation rate organizes convection cells in the liquid outer core. That's what creates the dynamo, which creates Earth's strong magnetic field. The book claims a large moon is extremely rare, so a terrestrial planet with a strong magnetic field is equally rare. The magnetic field prevents loss of water to space, so the magnetic field is responsible for our planet retaining liquid water.

But I'm claiming the same process can occur on a planet close to a red dwarf star. And Mercury is an example. A planet that close has tides, the rotational resonance of Mercury proves that. Those tides have a similar effect on the core, which causes a strong magnetic field. Mercury's isn't as strong as Earth's, but Earth is not synchronised with the Moon's rotation. The moon is synchronized, but the Earth isn't. That means gravity from the Moon is actively slowing the Earth's rotation even today, but not slowing the core. The only thing slowing the core is fluid friction. That creates a stronger magnetic field than Mercury. But a planet close to a red dwarf could be out of resonance, causing a strong magnetic field like Earth.

The other thing is a star provides a very great deal of energy. A rogue planet will be frozen. Space is just a few degrees above absolute zero, so the surface of a rogue planet will be very close to that. Look at Pluto, Quaoar, or Eris. Very cold requiring a great deal of energy to mine anything. And no sunlight for a greenhouse. No solar energy. No nothing. I could understand the argument for O'Neill colonies in asteroid belts, but not rogue planets.

JoshNH4H · 2013-10-07 22:09:50

Well, the primary argument for rogue planets is that they're there; Assuming that we'll master cheap fusion energy at some point (When exactly that point is is mostly irrelevant) that makes them more or less habitable, and resource pressures and the math of exponential expansion suggest that we'll have reason to eventually.

Void · 2013-10-09 10:18:09

In that distant future, I would also wonder if progress with understanding, and maybe even manipulating dark matter and dark energy would provide an energy source.

Terraformer · 2013-10-09 14:46:44

A WIMP annihilator? They *are* supposed to be their own antiparticle. I've read suggestions that they'll keep white dwarfs warm by reacting in the core, and much the same for ice planets with large iron cores that might emerge when the universe is a lot older.

JoshNH4H · 2013-10-09 23:23:07

Or, artificially, rather sooner than that

karov · 2013-10-10 04:14:17

- dark matter annihilation,
- black holes harvesting,
- reverse baryogenesis,
- "entropic everything" space-time manipulation...

... these sources of energy are possible, but indeed for ultracold bodies we need and we do have pretty Newtonian (17th century style ) Sci-Tech ENOUGH for terraforming and habitation:

- interstellar optics

a planet ,say, 2 ly ( 100-ish kAU ) from the Sun needs "only" 100 000 times wider then the planetary diameter mirror-or-lense to gether enough natural white light up to Earth's insolation / illumination levels. Sounds stupendously A LOT, but if optic material "butterfly wings" thin and light, or dusty plasma, this will take small asteroid / comet - worth of mass to have. And this above is if we rely upon only Sun for this, the Galaxy is awash with dispersed good EM radiation ready for concentration with cheap robust methods.

- gravitational energy utilzation

astronomic bodies never come alone -- they all have satelites or coorbitals. The galaxy is full of "dandruff" of rogue planets, comets, ... indeed the number of non-starbound bodies exceeds the systemic ones by 4-5+ orders of magnitude. Imagine powering civ and bio on Pluto-like system by siphoning the lesser bodies onto the bigger one via some electromagnetic braking mechanism. Paul Birch mentioned bringing down mass from the Moon by descending on Earth READY goods ( metals, etc. even slag ) and making 10exp13 J p.a. from this.

- planetary rotational energy

often comparable with the gravitational binding energy! Magnetised rotating bodies readily serve as giant dynamos of electric engines. Sometimes they have ready armature too - the Jupiter-Io plasma cord of 2 TW! per instance.

- interstellar tramways

pellet streams, multireflection transport systems - they'll move cargo AND energy on many many light years away - backwards and forwards. Such systems no matter whether enclosed into multi-LY long topopoli habitats could utilize the enormous energy of the speed differences between stars or substellar objects in the Galaxy.

- geothermal energy

abundant in even the ice dwarf planemos for billions of years. Every interstellar Europa- or Triton-like body having under the icy bark a liquid ocean, possesses also a liquid metal temperatures core beneath - itself a lunar mass with stellar surface temperatures. Geothermal could be refilled by artificial accretion of more and more mas softlanded onto/into the habitat underbody.

THUS and much more even without ANY nuclear tech - fission or fusion.

===

Back to Mercury.:

* David Semloh's design:

======================

https://groups.google.com/forum/#!topic … BQ-RtknNtI

https://groups.google.com/forum/#!topic … guypS-jd5k

https://groups.google.com/forum/#!topic … F5kv1mIauQ

https://groups.google.com/forum/#!topic … A6XgBmQnms

https://groups.google.com/forum/#!topic … 89UhRauelI

https://groups.google.com/forum/#!topic … Aa-vkrshkw

https://groups.google.com/forum/#!topic … FupIQ8hKI4

https://groups.google.com/forum/#!topic … o5hee39N44

======================

VERY interesting reading.

Short-sleeve environment only on two circumpolar spots of "only" 1 mln. sq.mi. each + the rest of 72+ sq.km. steaming, boiling wilderness with some oases... Beautiful!

Open-sky natural-like habitable world.

The atmosphere around WON"T in ANY case be obstacle before Mercurian mining industry. Atmospheres always pay off!

Paul Birch archive:

http://www.orionsarm.com/fm_store/Paul% … 20Page.htm

these links work.

Last edited by karov (2013-10-10 04:36:27)

New Mars Forums

Announcement

#1 2013-10-03 08:43:31

Areoforming Mercury

#2 2013-10-03 09:54:49

Re: Areoforming Mercury

#3 2013-10-03 10:26:06

Re: Areoforming Mercury

#4 2013-10-03 16:29:17

Re: Areoforming Mercury

#5 2013-10-04 06:43:06

Re: Areoforming Mercury

#6 2013-10-06 20:32:15

Re: Areoforming Mercury

#7 2013-10-06 21:10:30

Re: Areoforming Mercury

#8 2013-10-07 10:51:03

Re: Areoforming Mercury

#9 2013-10-07 11:48:11

Re: Areoforming Mercury

#10 2013-10-07 13:30:08

Re: Areoforming Mercury

#11 2013-10-07 20:17:11

Re: Areoforming Mercury

#12 2013-10-07 22:09:50

Re: Areoforming Mercury

#13 2013-10-09 10:18:09

Re: Areoforming Mercury

#14 2013-10-09 14:46:44

Re: Areoforming Mercury

#15 2013-10-09 23:23:07

Re: Areoforming Mercury

#16 2013-10-10 04:14:17

Re: Areoforming Mercury

Board footer