Ceres

qraal · 2008-01-18 15:35:48

Hi Antius

Thanks for the reply, but I have a few issues with the idea applied to small worlds like Ceres.

Firstly the column mass for Ceres' 0.028 g is HUGE and the scale-height, adjusted for small planetary radius, is larger than its physical radius - it would still be quite dense at the synchronous orbital altitude of 720 km, thus Ceres would fling its atmosphere into space like a huge sprinkler. Assuming Earth-like temperatures and pressures at the surface, of course.

Secondly, the column depth means the atmosphere would attenuate sunlight incredibly - even more than sunlight is attenuated at sunset, for example. I'm not sure what that would do for habitability, but it wouldn't be good.

Thirdly, just how does the magnetic trapping work? We're talking about magnetically trapping ions at the top of the atmosphere? Make them fast enough and they would hold atmosphere in just like a plasma window keeps air out of a vacuum chamber, but that's one heck of a "plasma window"!

nickname · 2008-01-18 16:46:14

Hacking a bit at the C02 math.
Ceres being a mean temperature of -100°C.
With 1 bar of C02 at Ceres adding around 70c, we end up with a world somewhere around -30c.

A mix of super greenhouse gasses or methane in the atmosphere and it's not beyond the realm of being a world above 0c.

As we get further out in the solar system the numbers become more dismal for C02.
Moons around Jupiter will require 2 or 3 bars of C02 to have a hope of being a 0c place.
Around Saturn more like 10 bars of C02.

Ceres and Mars might be the only places a C02 atmosphere is useful.
My guess is that Mars is the only useful place to try and have a 1 bar C02 atmosphere, Ceres is a big effort for a small place.

My guess as a minimum bearable temperature for humans is around -70c since Eskimo's go indoors at those temperatures.
We could probable add another -30c to that with heated suits, that puts us at around -100 as a minimum bearable temperature for both men and machines on a moon or planet surface.

qraal · 2008-01-18 18:07:09

Hi All

According to Jim Kasting's models CO2 starts turning into ice clouds at about 0.5 Earth insolation levels, and at 0.36 Earth insolation the cloud cover becomes total. No further pure CO2 greenhouse is possible, so the atmosphere would need super-greenhouse gases like ammonia, methane and fluorocarbons.

Hacking a bit at the C02 math.
Ceres being a mean temperature of -100°C.
With 1 bar of C02 at Ceres adding around 70c, we end up with a world somewhere around -30c.
A mix of super greenhouse gasses or methane in the atmosphere and it's not beyond the realm of being a world above 0c.

By themselves CO2 ice clouds are brilliant IR scatterers BUT the surface is potentially very dark as the ice crystals are big - look at the recent views of CO2 ice cloud shading on the surface of Mars seen by Mars Express.

As we get further out in the solar system the numbers become more dismal for C02.
Moons around Jupiter will require 2 or 3 bars of C02 to have a hope of being a 0c place.
Around Saturn more like 10 bars of C02.

As I said the modelling indicates we'd need to be using methane and ammonia. Jonathan Lunine and Ralph Lorenz modelled Titan's atmosphere under a ~ 5 bar (!) CH4 atmosphere and only got a 50 C rise out of it because of the counteracting effect of tholin haze production. If the Sun was cooler - or we put a big filter in place - the tholin problem would go away and the surface temperature would go way up. Modelling of a haze free Titan atmosphere in the 1970s got the surface temperature up to 155 K in a 0.5 bar CH4/H2 atmosphere. In the late 1970s there was thermal data suggesting a 200 K surface temperature on Titan, which needed a 21 bar nitrogen atmosphere to be possible. Based on ammonia levels in the ices that should be possible to generate.

My guess as a minimum bearable temperature for humans is around -70c since Eskimo's go indoors at those temperatures.
We could probable add another -30c to that with heated suits, that puts us at around -100 as a minimum bearable temperature for both men and machines on a moon or planet surface.

There's a Siberian town which gets down to ~ -60 C or so during winter, so I don't doubt the temperature you quote. Earth's lowest ever is ~ -87 C, at altitude on an Antarctic mountain, so the heavy N2 atmosphere of Titan would be about right.

Terraformer · 2008-01-19 05:02:44

I thought Ceres maximum temp. was -37 c. That was what the internet told me.

And, as I've said before, Ceres has a thick mantle of water ice that could be turned into a salty conductor to get a mag. field.

nickname · 2008-01-19 07:43:18

qraal,

Oh i agree C02 is going to run out it's usefulness pretty quick.

Methane and fluorocarbons have a set of problems themselves, like on Titan with smog.

Methane with no fluorocarbons is probably a pretty good choice.

Ammonia might be a good choice as a long term way to warm up a moon.
With ammonia we have the problem of having going to get it.

Another option is to tweak the C02 release into a super greenhouse gas release.

As for temperature just guessing at the minimal temperatures humans could endure for a few hours.
Machines can be a bit more enduring to temperature than humans but not a lot.
I have experienced -54c in Northern Ontario on a calm day, it wasn't as cold as you would think until the wind picked up.
Then it was bone chilling, so wind speed will play a big role in what is bearable outdoors.
-60 -70 pretty typical in far northern Canada, it's just not that much warmer than Vostok with an all time low temperature of -89.4 °C.

Terraformer,

The average temperature i got for Ceres was -100.
I didn't check for high temperatures but if it's -37 then 1 bar of C02 would melt much of Ceres.
Melting part of Ceres would alter the math completely just from released elements.
Maybe 1/2 bar C02 would get a melt going in places.

A similar very complex math comes into play on Mars at around 50-100mb of C02 at around the melt point of some areas.
Lots of guesswork at that point as to what gets released and what it does to increase more releases.

Terraformer · 2008-01-19 08:34:19

It doesn't have to be that warm. Don't want to end up with a water world.

So, if we're aiming for a 650 millibar atmosphere, 250 mb of Oxygen, 50 mb of CO2 (don't know whether humans can survive that, probably has to be lowered), and the rest Supergreenhouse gasses? Anyone know how to work out the atmospheres height?

qraal · 2008-01-19 17:25:46

Hi All

Anyone know how to work out the atmospheres height?

Atmospheric pressure and density fall-off exponentially - for every increment of what's called the scale height the pressure/density decrease by a factor of e (=2.71828...) The scale height is height(z) at which the gravitational potential (with respect to the surface) equals the average molecular energy (kT) of the gas:

mgz = k.T

...BUT that's the non-varying surface gravity approximation. To work it out for small planets you have to use the gravitational potential in a radial force field. Sounds imposing but it's just V = GM/R, where G is Newton's constant, M is the planet mass, R is the radial distance. After a bit of fiddling I get:

mgzR/R(s) = kT

...where R is the radius of height z, g the surface gravity, R(s) the surface radius. Plugging in the numbers for Ceres (Earth normal gas, T= 288.15 K, m = 28.96, g= 0.27 m/s^2) we get z = 304 km. But the gravitational potential doesn't decline linearly with radius anymore. To work out how much the pressure declines for an isothermal atmosphere we get:

P = P(0).e^-(z/z(0)) (non-radial case)

P = P(0).e^-(z/z(0)).(R(0)/R) (radial case)

...as you can see the radial gravitational field's pressure declines slower because it's reduced by the R(0)/R factor (R(0) being the first scale height's radius, R being the altitude we want the pressure at.) So for Ceres at an altitude of 714 km, the pressure has dropped to 38.8% of its surface value (Ceres radius 483 km)...

Except we didn't take the rotation of Ceres into account and at 714 km altitude is the synchronous orbital altitude - any gases feel effectively zero gee. Beyond that altitude and the gases feel a net acceleration away from Ceres. Thus my reason for calling Ceres' atmosphere a gigantic sprinkler flinging gas into space. I'm not sure how strong a magnetic field would hold that in either.

So, if we're aiming for a 650 millibar atmosphere, 250 mb of Oxygen, 50 mb of CO2 (don't know whether humans can survive that, probably has to be lowered), and the rest Supergreenhouse gasses?

A partial pressure of 50 mb CO2 is about the maximum tolerable, and even then a lot of people would feel shortness of breath, headaches and so on. Super-greenhouse gases don't need to be present in such great numbers - microbars usually will do. A surface pressure of just 300 mb total is probably fine so long as it's not too cold.

karov · 2008-01-20 04:47:26

very correct points, qraal! thank you.
I`ll go in details ( hopefully) soon, but what about magnetosphere bubble of tens of thousands of km radius?

The atmospheric attenuation of the sun light -- that happens everywhere here some dozens of meters under the water surface... Given the 0.03 gees the Cerean solid surface would be more like the bottom of an atmospheric ocean -- but better oxigenated.

karov · 2008-01-20 14:10:38

Plasma window.

What are the parameters power consumption vs. area vs. pressure gradient...???

btw, seems like good tool for

1. gas ( plasma ) core fission rocket

2. for separation of plasmed elements...

3. "pipes" for atmosphere syphoning,

4. etc. , etc.

For Ceres -- even sprinkling away atmosphere via axial rotation -- what would be the gas pressure of the 'surface' of gas bubble with radius of 10 000 km? around Ceres ( or whatever )? I expect the ambient pressure to not be higher than the Earth one at several hindred kilometers hight... hence pretty modest power needs to keep the air around.

Yes, the spacecraft and other plasma shield needs wires / mesh / electrodes to do confinement of several kilos of hydrogen plasma ... but the mesh could be substituted with dusty plasma hexagonal "convection patterns".

Ceres leaking its atmosphere up into solar co-orbit continuously re-supplies its plasma shield / shell with substance...

That info about such plasmoids as plasma windows, confirms my confidence that the plasma is full scale HARDWARE material.

Idea -- plasma windows are stated to focus particles, EM, etc. The 1000km Ceres provided with the resp. times wider focusing atmosphere will be supplied with enough filtered and cnditioned solar illumination. The plasma shield ( artificial magnetosphere = PLASMOID again ) could have the topology to utilize solar wind.. The particle focusing abilities + multilayered plasma window + the abundant EM radiation source the Sun, could be used for chemical atmosphere processing --- plasmic "photosynthesis" braking CO2, H2O, recombinations...

qraal · 2008-01-20 15:22:24

Hi Karov

Gases exerting a pressure need a counter-force so they don't expand away into space...

For Ceres -- even sprinkling away atmosphere via axial rotation -- what would be the gas pressure of the 'surface' of gas bubble with radius of 10 000 km? around Ceres ( or whatever )? I expect the ambient pressure to not be higher than the Earth one at several hindred kilometers hight... hence pretty modest power needs to keep the air around.

...the problem is that 714 km up there's no effective gravity on the gas anymore. Nothing to provide a counter-force to its free expansion into the void. Simple fact of physics is that gas at any reasonable temperature has too much internal energy to be kept against Ceres by gravity alone. Only an Air-Shell will keep the pressure on the surface.

Look at it this way. What's the gravitational potential of Ceres at its surface? Just 133,450 J/kg. Earth is 62.5 MJ/kg and the Moon is 2.8 MJ/kg. The internal energy of air at 288.15 K is 291,800 J/kg - much less than the potential of the Moon or the Earth, but more so than Ceres. That air has enough energy to leap into space.

Of course as it expands the stuff does work against itself and it cools down. But, at the same time, it's absorbing heat from the Sun, so maybe it doesn't cool down very much at all. Thus why I assumed an isothermal atmosphere originally. And my point is that air at reasonable temperatures has enough energy to easily escape Ceres. The gravity of Ceres isn't enough to attenuate the gas at the altitude we want a plasma "shell" to operate.

Antius · 2008-01-20 16:35:49

A good analysis. At ionosphere heights, the average speed of the ions will greatly exceed those of ordinary atmospheric gas molecules, so the situation is even worse than you've suggested. The only thing constraining gas molecules from escaping is collision with other gas molecules. The atmosphere would evaporate like a pan of boiling water. But, only the molecules at the top of the atmosphere have a free path, so the whole process would take time and the species escaping would be ions.

A magnetic field would trap the ions and they would spin along the field lines until they reenter the atmosphere at the poles. Another potential problem is the temperature of the ions. Ions within the upper atmosphere tend to thermalise through collision with other ions and gas molecuiles which keeps their average temperature relatively low. As escaping atmospheric ions spread out across space, they would absorb energy from solar wind particles and UV. This will increase their average temperature far above that of the upper atmosphere. As the ions spiral down the magnetic field lines and reenter the atmosphere, they would reemit their accumulated energy as heat and light. If the catchment area of the ions is too large, they would emit enough stored energy to create a serious problem for anyone or anything living on the surface.

For outer solar system worlds that happen to be a long way from the sun, the magnetic field provides a convenient mechanism for increasing their catchment area to solar radiation. For Ceres, with a solar intensity ~1/9th that of Earth's it could end up litterally frying the place.

Antius · 2008-01-20 17:39:41

Here is a wacky idea. Sunlight is generally too weak to support a diverse ecosystem beyond the orbit of Mars. At Ceres distance from the sun, it is just 1/9th the value at Earth's orbit. To provide a 1 bar atmospheric pressure, we would need a column density 30-40 times that of Earth. The gravity is just too weak to make terraforming Ceres economic compared to sealed rotating habitats. Graals figures suggest that it is not feasible - the gravity is just too low to allow significant atmospheric retention.

One alternative would be to encase the world in a shell of metal. Sunlight is so weak at that distance from the sun that it almost wouldn't matter whether the shell was opaque or not. A few inches of iron will be a lot cheaper to provide than hundreds of tonnes per square meter of oxygen gas. Robots would roam the inner and outer surface of the shell. If any part of the shell were punctured by a meterorite, robots on the outer surface would gradually weld the hole shut, so the shell would have the ability to 'heal'. On the inner surface of the sphere, gas bag robots would roam. In respose to a large meteorite, the robots would accumulate around the mouth of the puncture and would inflate their gas bags, effectively sealing the puncture until the external welders repair the shell. A shell 1 mile from the surface could be anchored in place by steel supports spaced every 100km or so. Column density would be reduced to less than 3 tonnes per square meter for a 1 bar pressure. For a 300mb atmosphere of pure O2, column density goes down to less than 1 tonne per square metre.

The inner surface of the iron sphere would be painted blue or conditioned with glass and artificial lighting to provide a blue sky. Light would be provided by collections of LEDs or other light emitting devices. These could be combined to produce a precise solar visible spectrum, indistinguishable from real sunlight. Clouds could be produced by spraying water from pipes along the inner surface of the sphere.

Power could be provided on a planetary scale by large fusion reactors. The capital costs of fusion reactors decreases with increasing size and the specific power output increases. Plasma leakage also decreases with increasing size. The implication is, that fusion reactors in the tens or hundreds of gigawatt size should provide power at low cost.

qraal · 2008-01-21 05:58:06

Hi Antius

I'd like to see hard data on growth in low light before I have a real opinion on the "not enough sunlight for growth" claim you make. Plants with plenty of sunlight often have a hard time using it because of evaporation and over-heating. And how much of the Sun's incoming energy do they actually use? Perhaps in low light they can be tweaked for higher efficiency. That's my particular take on this matter.

But to illumine Ceres wouldn't take a vast soletta anyway, so I think the difficulty is more imagined than real. Consider a transparent shell at synchronous altitude (lowest stress position for it IMO) - the shell also acts as a light collector through tricky surface coatings and bounces incoming light towards the surface. Easy. If we can make a transparent shell 2400 km wide then we can do the optics too.

Problem is: what sort of bursting strength do we need to keep the air in?

nickname · 2008-01-21 07:11:53

Cyanobacteria will grow at 1/9 light levels, they do in the water column on Earth.
Since the surface of Ceres above 0c would be water we would select it.
Not much point in looking at surface plant endurance for a place that won't have a surface.

Antius · 2008-01-21 07:43:20

Hi Antius
I'd like to see hard data on growth in low light before I have a real opinion on the "not enough sunlight for growth" claim you make. Plants with plenty of sunlight often have a hard time using it because of evaporation and over-heating. And how much of the Sun's incoming energy do they actually use? Perhaps in low light they can be tweaked for higher efficiency. That's my particular take on this matter.
But to illumine Ceres wouldn't take a vast soletta anyway, so I think the difficulty is more imagined than real. Consider a transparent shell at synchronous altitude (lowest stress position for it IMO) - the shell also acts as a light collector through tricky surface coatings and bounces incoming light towards the surface. Easy. If we can make a transparent shell 2400 km wide then we can do the optics too.
Problem is: what sort of bursting strength do we need to keep the air in?

Ceres equatorial illumination levels are 0.075kwh/m2/day. That is comparable to winter illumination levels in England. Crops will grow under those conditions if provided with adequate water and optimum temperatures. But growth is generally retarded by lack of light. Further from the sun than Ceres and sunlight becomes too weak to be of great value. Even at Ceres distance, the productivity of the ecosystem would be low and would become zero abovce a certain latitude. So the holding capacity of Ceres would be much smaller than an equivelant amount of land on Earth, or even on Mars. Yet the difficulty of terraforming ceres might be an order of magnitude higher.

I realised today that a roofed world would be exceptionally vulnerable to impacts. A large explosion on the surface, would send shockwaves through the atmosphere, ripping off the iron roof hundreds of kilometres from the impact site. So a roofed world house isn't really a sensible option. This would also be a problem for sealed O'Neill type colonies. As a metoer passes through the outer shell, it would compress the air within the habitat and fracture the hull. Rather like a bullet passing through an apple, the meteor would not leave a neat hole.

qraal · 2008-01-21 14:11:38

Ceres equatorial illumination levels are 0.075kwh/m2/day. That is comparable to winter illumination levels in England. Crops will grow under those conditions if provided with adequate water and optimum temperatures. But growth is generally retarded by lack of light. Further from the sun than Ceres and sunlight becomes too weak to be of great value.

Perhaps, though I would still like to see hard data.

Even at Ceres distance, the productivity of the ecosystem would be low and would become zero abovce a certain latitude. So the holding capacity of Ceres would be much smaller than an equivelant amount of land on Earth, or even on Mars. Yet the difficulty of terraforming ceres might be an order of magnitude higher.

What do you think of improving plant efficiency? Another thought I had was the attenuated light levels parallel the low light of the lower levels in a gallery forest.

I realised today that a roofed world would be exceptionally vulnerable to impacts. A large explosion on the surface, would send shockwaves through the atmosphere, ripping off the iron roof hundreds of kilometres from the impact site. So a roofed world house isn't really a sensible option. This would also be a problem for sealed O'Neill type colonies. As a metoer passes through the outer shell, it would compress the air within the habitat and fracture the hull. Rather like a bullet passing through an apple, the meteor would not leave a neat hole.

O'Neill colonies and roofed Worlds would need active defense systems, like automatic lasers and/or kinetic interceptors (rapid-fire rail-guns, which don't yet exist.) But also a multi-layer Whipple shield of nanotube fibre would stop most impactors.

nickname · 2008-01-22 06:59:18

I think an artificial roof on ceres wouldn't work simply because of the air leaks.
If you add up all the joins such a structure would need the escaping atmosphere would never be controllable.

Even a double layered roof will leak just as bad as a single layered roof because of the difference in bar pressure of the inside to outside.
The area between the two layers will simply pressurize to whatever the lower layer is, then leak to the outside at the same rate as a single layer.

Antius · 2008-01-22 17:40:42

I think an artificial roof on ceres wouldn't work simply because of the air leaks.
If you add up all the joins such a structure would need the escaping atmosphere would never be controllable.
Even a double layered roof will leak just as bad as a single layered roof because of the difference in bar pressure of the inside to outside.
The area between the two layers will simply pressurize to whatever the lower layer is, then leak to the outside at the same rate as a single layer.

All atmospheric retention methods are likely to be highly imperfect on Ceres. The biosphere would require occasional topping up with fresh gas, just as the Earth does. The question is, would leakage rates from a 0.1-1tonne/sq metre column density physically contained atmosphere, exceed those of a 100tonne/sq meter magnetically confined atmosphere?

The problem with any sort of roof world is that it is exceptionally vulnerable to damage and very difficult to engineer in a safe and sustainable way. Even relatively small impacts would tend to be disproportionately destructive and it would be very difficult to protect a 1000km diameter world from all impacts with the sort of reliability that one would need to create a biosphere on geological timescales. Multiple independent cells would work much better than a single world house, given that each could be seperated by a barrier of vacuum. But then we should ask the question as to why the cells need to be on Ceres in the first place? Why not just build self-enclosed colonies in space and use rotation to produce whatever gravity you need and mirrors to provide however much sunlight is needed?

Any form of natural terraforming even with the aid of super-strong magnetic fields, would be extremely expensive on Ceres. There are uncertainties as to whether it would work at all and the value of the land created under such a deep and poorly transparent atmosphere is open to question.

I think the same will end up being true of many other potential terraformable worlds. Some of the icy worlds in the outer solar system have gravitational fields considerably deeper than Ceres. But these worlds would be constrained to being as cold as Siberia, even with the aid of significant artificial illumination. Soil would be available in limited quantities from meteorite dust, but ambient temperatures would be far too low for anything to grow. Holding capacity of the land would be low at best. So we come back to growing things in greehouses under artificial conditions, not really a great step forward from having domes on a non-terraformed world. Again, it is difficult to see how the value of the land could ever justify the cost of carrying out such an enormous terraformation effort.

At this point somebody usualy chirps up that a terraformed iceball would be sustainable on geological timescales whereas man made space based habitats would not. But it is questionable whether a terraformed dwarf planet would really offer that many advantages in terms of endurance to catastrophe. A large impact would devastate any ecosystem established on the world, kill the vast majority of people living there and would very likely blow away a significant portion of the atmosphere. And we shouldn't forget that most such worlds will require considerable human maintenance to maintain life permitting conditions. A terraformed Triton or Pluto would need artificial illumination as a substitute for sunlight (which is only 10 times brighter than moonlight at their distance from the sun). Could we engineer such a complex system to be invulnerable to catastrophic impacts on a geological timescale?

A large impact would very likely destroy an O'Neill habitat in its entirety. But the fact remains that we would not be living in just one such habitat but thousands or millions. As such we have a large degree of redundancy. The bottom line will come down to cost. Do we spend x producing y square miles of tundra or the same amount of resources producing a far larger quantity of far more desirable land?

nickname · 2008-01-22 18:43:27

Antius,

Oh i agree that most of the places in the solar system that could be altered to suit us would take such an effort and cost to do that they probably will never be done.
And what is the resulting world after many thousands of years of effort?
Probably like you say a poorly lit and cold place like Siberia in winter.
Not to many people vacationing in Siberia in winter. LOL

Most of those worlds just a few meters under ground and it's a completely different way to set up a colony.

Even on Mars it makes quite a bit of sense to just select a crater and build what you want inside it.
Then bury the entire thing in a few meters of soil.
Easy warming, radiation protection, internal pressure problems are resolved just doing that.
Growing plants can be a totally indoor thing with power from solar panels on the surface or a small nuclear reactor on the surface.

I have a feeling that is how mankind will slowly move to the places in the solar system.

The sheer efforts in trying to terra form even Mars the easiest candidate are very daunting.
Just warming Mars is an effort beyond anything mankind has done, after that is complete bringing up the nitrogen content so the gas balance can be non lethal.
Waiting a few 10,000s of thousands of years for cyanobacteria to convert C02 into oxygen so the C02 and oxygen levels are safe for land life, then a few more 1,000s of thousands of years for land life to cover Mars so it's safe for animal life.

Seems like such a big effort when a few holes in the ground produce the same results on a small scale.

Some day someone might come up with an anti gravity machine that makes terra forming a much more simple procedure.
That machine would also make visiting other stars a much more simple procedure, so maybe we will never terra form anything.
Or maybe just nothing in our solar system.

qraal · 2008-01-22 19:55:28

Hi Guys

I think the distinction between terraformed, orbiformed and artificial worlds is pointless. Arguing for one or the other is stupid because neither has been achieved yet. The first habitats will be on natural bodies, but if we're talking asteroids they won't stay "natural" for long, as the whole thing is either mined or converted. I've often wondered just what O'Neill style Free-Space colonies were supposed to live off in terms of natural resources - which they don't have. Why is an L4 colony preferable to a Moon City? Or a multi-level converted asteroid? Our gravity-prejudiced preferences focus on big, flat living spaces, and that's what O'Neill wanted to dangle as a carrot to the human race, but his was a Utopian dream with no idea what real "life in space" would mean.

So I tend to remain very sceptical of the whole O'Neill thing, as much as I loved the art-work and romantic idealism when I was a kid. Now it just seems like - literally - castles in the air. If people choose to live in low gravity then they'll find ways around its deletrious effects and the idea of rotating cylinders and spheres full of empty air will just seem silly and wasteful.

At the same time I suspect there will be an urge to shame other celestial bodies to something more like Earth, and efforts to do so on a mass-scale. Whether it's via orbiforming, World-Houses or terraforming is not ours to decide here and now. We're trying to delineate the possible not set-in-stone what's desirable.

As for Ceres, physics is telling us that a gravity-constrained atmosphere isn't possible. I don't believe the magnetic field thing will work either, but my magnetic theory skills are pretty weak. I suspect the required fields would be intense and unlikely to be produced on a planetary scale. Maybe someone will invent a Jack Williamson-style "paragravity generator" to terraform asteroids, but for now only shells, domes and tunnels will work to keep air in - on whatever scale the Belters desire.

nickname · 2008-01-24 06:33:48

qraal,

Antius probably has a pretty good point about gravity and humans.
I bet we are very poorly adaptable to much less than 1g for long periods of time.

Even short space shuttle rides tend to point out that fact that we immediately start to adapt in unhealthy ways.

I have the feeling that people staying on the moon or Mars for long durations will be sleeping in centrifuges to compensate.

Those first visitors to Mars might find that a 18 months stay is a death sentence.
18 months at 1/3 g we just don't know the results on a human body.

I also agree about the terra form, orbiform or artificial world distinctions being silly.

In my opinion we have no candidate for terra forming in our solar system.
Venus is the only place that has the right stuff and size for terraforming, but we won't be terraforming it in any near future.

We already have one world Titan that is a good example of what to expect in the outer solar system with altering moons.
Siberia in winter is a much nicer place than Titan.

We have no reason to make spinning space stations or living in spinning asteroids, although the idea is interesting the reasons to do either eludes me.
Above ground domes will only work on places with decent bar pressure (titan).
So we are left with only holes in the ground as our option.

Holes in the ground are a pretty good option though for asteroids, moons and planets.
Holes in the ground are cheap, require little cost or equipment and little startup time.

The Swiss cheese plan for colonization.

Gregori · 2008-01-25 01:54:05

Since we're talking about absurd things here:

Who here think Ceres would look nice parked in Mars Orbit? Give mars a decent sized moon for a change!!!

Terraformer · 2008-01-25 06:07:50

Absurb things? What absurb things? Nothing absurb here.

Shame other worlds to something like ours? What?

Antius · 2008-01-25 06:23:29

Bed rest provides a good simulation for the decay of the body under weightless conditions. Most people recover from extended periods of bedrest, but muscletone deteriorates quite rapidly, begining within 6 hours or so. My girlfreind wrote her final year dissertation on the effects of microgravity on the human body. Eighteen months in 1/3rd g certainly won't be a death sentence, but will result in varying degrees of muscle loss which may take some months to recover from.

Lunar and Martian conditions will clearly be less severe than microgravity. Martian gravity may be sufficient to prevent severe deterioration of the body if a modest amount of exercise is taken each day. This would become an integral part of Martian culture. Generally, a sedentary lifestyle can be expected to have more severe consequences on Mars than on Earth.

Antius · 2008-01-25 07:01:41

Hi Guys
I think the distinction between terraformed, orbiformed and artificial worlds is pointless. Arguing for one or the other is stupid because neither has been achieved yet. The first habitats will be on natural bodies, but if we're talking asteroids they won't stay "natural" for long, as the whole thing is either mined or converted. I've often wondered just what O'Neill style Free-Space colonies were supposed to live off in terms of natural resources - which they don't have. Why is an L4 colony preferable to a Moon City? Or a multi-level converted asteroid? Our gravity-prejudiced preferences focus on big, flat living spaces, and that's what O'Neill wanted to dangle as a carrot to the human race, but his was a Utopian dream with no idea what real "life in space" would mean.
So I tend to remain very sceptical of the whole O'Neill thing, as much as I loved the art-work and romantic idealism when I was a kid. Now it just seems like - literally - castles in the air. If people choose to live in low gravity then they'll find ways around its deletrious effects and the idea of rotating cylinders and spheres full of empty air will just seem silly and wasteful.
At the same time I suspect there will be an urge to shame other celestial bodies to something more like Earth, and efforts to do so on a mass-scale. Whether it's via orbiforming, World-Houses or terraforming is not ours to decide here and now. We're trying to delineate the possible not set-in-stone what's desirable.
As for Ceres, physics is telling us that a gravity-constrained atmosphere isn't possible. I don't believe the magnetic field thing will work either, but my magnetic theory skills are pretty weak. I suspect the required fields would be intense and unlikely to be produced on a planetary scale. Maybe someone will invent a Jack Williamson-style "paragravity generator" to terraform asteroids, but for now only shells, domes and tunnels will work to keep air in - on whatever scale the Belters desire.

Zero-g clearly has a lot of advantages for large-scale engineering. And solar power is available all of the time without interuption in free space. So the O'Neill idea makes a lot of sense from this point of view. Raw materials will be relatively expensive, as they would need to be imported from the moon or asteroids, but energy would be relatively cheap.

I personally think that the habitats will end up being different from what O'Neill imagined. Initially they will be a lot smaller than his 500m diameter sphere and will tend to be engineered to optimise their interior volume. The sphere will be decked out internally to provide maximum possible habitation space for the minimum capital investment. The sort of Earth-like internal spaces he envisaged would be expensive to engineer even if lunar/asteroid materials were cheap. They will also be dosy places to live, given that high cost of providing the 3t/m2 cosmic ray shielding, will probably neccesitate unshielded habitats initially.

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#51 2008-01-18 15:35:48

Re: Ceres

#52 2008-01-18 16:46:14

Re: Ceres

#53 2008-01-18 18:07:09

Re: Ceres

#54 2008-01-19 05:02:44

Re: Ceres

#55 2008-01-19 07:43:18

Re: Ceres

#56 2008-01-19 08:34:19

Re: Ceres

#57 2008-01-19 17:25:46

Re: Ceres

#58 2008-01-20 04:47:26

Re: Ceres

#59 2008-01-20 14:10:38

Re: Ceres

#60 2008-01-20 15:22:24

Re: Ceres

#61 2008-01-20 16:35:49

Re: Ceres

#62 2008-01-20 17:39:41

Re: Ceres

#63 2008-01-21 05:58:06

Re: Ceres

#64 2008-01-21 07:11:53

Re: Ceres

#65 2008-01-21 07:43:20

Re: Ceres

#66 2008-01-21 14:11:38

Re: Ceres

#67 2008-01-22 06:59:18

Re: Ceres

#68 2008-01-22 17:40:42

Re: Ceres

#69 2008-01-22 18:43:27

Re: Ceres

#70 2008-01-22 19:55:28

Re: Ceres

#71 2008-01-24 06:33:48

Re: Ceres

#72 2008-01-25 01:54:05

Re: Ceres

#73 2008-01-25 06:07:50

Re: Ceres

#74 2008-01-25 06:23:29

Re: Ceres

#75 2008-01-25 07:01:41

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