Which of the Galilean moons could we Terraform, and why?

[lajoswinkler]

Ganymede has a higher surface gravity. It would help with the atmosphere retention. Ionizing radiation isn't that bad. 80 millisieverts per day is 4.16 microsieverts per hour. It's perfectly manageable (0.2 microsieverts per hour - that's my local dose here) and it will be orders of magnitude less if you're not tiptoeing through the tulips outside all the time and you mostly work inside.

Edited February 22, 2016 by lajoswinkler

[Spaceception]

6 hours ago, lajoswinkler said:

Ganymede has a higher surface gravity.

Yeah, by 2%.

[lajoswinkler]

48 minutes ago, Spaceception said:

Yeah, by 2%.

It's something.

[AngelLestat]

A thick atmosphere will reduce the radiation problem, and you need a really thick (full of greenhouse gases) atmosphere to provide some surface heat.
Water vapor is something that we can breath, but we need to prevent to form clouds or it will reflect the few sunlight we receive.
We need to search other greenhouses to help in this matter in a way that will not be toxic.
We can not solve the gravity problem, Io has the highest surface gravity, then the moon and other bodies.
So the only way to solve the gravity is with spinning habitats tilted, like a train habitat with tilted rails, the small difference in gravity between these moons does no really matter unless it helps to keep the atmosphere.
IO has internal heat that can be useful, no sure about its other resources.
 

Edited February 22, 2016 by AngelLestat

[Spaceception]

20 minutes ago, AngelLestat said:

A thick atmosphere will reduce the radiation problem, and you need a really thick (full of greenhouse gases) atmosphere to provide some surface heat.
Water vapor is something that we can breath, but we need to prevent to form clouds or it will reflect the few sunlight we receive.
We need to search other greenhouses to help in this matter in a way that will not be toxic.
We can not solve the gravity problem, Io has the highest surface gravity, then the moon and other bodies.
So the only way to solve the gravity is with spinning habitats tilted, like a train habitat with tilted rails, the small difference in gravity between these moons does no really matter unless it helps to keep the atmosphere.
IO has internal heat that can be useful, no sure about its other resources.
 

So if Io has an atmosphere about as thick as Earths. What would its RAD intake be, and what would its temperature be (Assuming it's mostly CO2)?

Also, Doesn't Io have the highest gravity of any Moon in the solar system?

Edited February 22, 2016 by Spaceception

[lajoswinkler]

If you elevate the temperature of those icy satellites, you'll have to deal with mud and seas.

[Spaceception]

7 minutes ago, lajoswinkler said:

If you elevate the temperature of those icy satellites, you'll have to deal with mud and seas.

So raise the temperature to where it's well below freezing (But still much warmer) so it's covered in ice, or well above freezing so that it's an Oceania.

[AngelLestat]

40 minutes ago, lajoswinkler said:

If you elevate the temperature of those icy satellites, you'll have to deal with mud and seas.

good point.

No sure why Titan has a 1.5bar atmosphere with lower gravity than Io, however this lost all its atmosphere in its orbit and then is sucked by jupiter magnetic fields.
But in any case, IO sulphur does not help, because combined with water reflect the light. (and there is no much water anyway).
I guess is no possible to terraform any of the bodies of the solar system without import elements from different places (no just the asteroids).

49 minutes ago, Spaceception said:

Also, Doesn't Io have the highest gravity of any Moon in the solar system?

that is what I said..  or no?

Edited February 22, 2016 by AngelLestat

[sevenperforce]

Someone should come up with a list of possible atmospheric compositions, temperatures, and pressures which are survivable for humans.

For example, is there anything other than nitrogen which will work as an inert gas? 

[fredinno]

This may be of use:

http://terraforming.wikia.com/wiki/Callisto

22 hours ago, peadar1987 said:

Well it's mostly water ice and rock, so you'd need a huge amount of gas. Your criteria require something that's common, noncorrosive and an extremely powerful greenhouse gas. It should also be readily available in the outer solar system, you don't want to be shifting large amounts of mass around the place.

From this page: https://en.wikipedia.org/wiki/Global_warming_potential I'm thinking your best bet is probably Nitrous Oxide: https://en.wikipedia.org/wiki/Nitrous_oxide. Boiling point of -88 celsius at atmospheric pressure, so should be a vapour at Callisto's surface temperature of roughly -100. Global warming potential of roughly 300 times that of CO₂. Nonflammable, and not particularly corrosive at low enough partial pressures.

The main problem with this would be finding suitable amounts of nitrogen. Oxygen could be cracked from the water of Callisto. Probably your best bet would be to redirect a small Kuiper Belt object, or a Neptune Trojan onto a collision course.

So now some numbers (all data from the excellent Wolfram Alpha: wolframalpha.com). In order to walk outside with no pressure suit, you need about 7% the atmospheric pressure of earth. Atmospheric pressure depends on the weight of the air column above you, which depends on the gravity of the body, so on Callisto, with a surface gravity 12.6% that of earth, you would need a column of air above you with a mass 55% of what you have on earth. Luckily, Callisto has a surface area just 14% of earth, so assuming the atmosphere is thin in comparison with the radius of the moon, it will need an atmosphere with a mass of (0.55*0.14) that the mass of the earth's atmosphere, which gives you 4*10¹⁷kg. You'd only need to import 2/3 of this if you were reacting it with locally sourced oxygen, so you end up with roughly 3*10¹⁷kg. That's a big chunk of ice, but there are probably plenty of them in the Kuiper Belt or at the Trojan points of Uranus and Neptune, and it's only 3 millionths the mass of Callisto itself. Redirecting such a huge thing takes a tremendous amount of energy though. Giving it a kick of just 100m/s, which might be enough to bring gravity assists from Neptune into play, would take 1.5*10²¹ J of energy. To do it over the course of 10 years would require a constant input of 5*10¹³W, or 50TW. Earth's current annual energy consumption is about 16TW.

Once you smash your KBO into Callisto, you drop huge reactors onto the surface to process the atmosphere and the water ice into N₂O and wait for them to do their jobs.

This is a monster of a project, and it's not going to be happening any time soon!

The best GHG is Sulfur Hexaflouride.https://en.wikipedia.org/wiki/Sulfur_hexafluoride#Greenhouse_gas

22 hours ago, peadar1987 said:

Yep, but the further in towards the sun you get, the less icy and more rocky the bodies. If you're looking for any old impactor, a Jupiter Trojan would be your best bet. If you want lots of nitrogen, you're going to have to go further out to either Uranus/Neptune Trojans, or KBOs.

The alternative would be to try and mine it from Callisto instead, although that is in itself a mammoth task. The world's largest open pit mine has removed 1.2*10¹²kg of iron ore since operations began in the late 1800s: https://en.wikipedia.org/wiki/Hull%E2%80%93Rust%E2%80%93Mahoning_Open_Pit_Iron_Mine

You'd need 25,000 of these mines to just dig up the mass of the atmosphere you would need. That's before you start to consider how much of what you dig up is actually useful material for producing an atmosphere. I'd be inclined to say doing the job in one go with a massive suitable impactor is the easier of the two options.

Well, you can just first melt the planet with a glass covering (essential to keep the atmosphere in) and then https://www.google.ca/search?q=density+of+liquid+ammonia&ie=utf-8&oe=utf-8&gws_rd=cr&ei=CT3LVoavNMLAjwOV6pCIBg https://www.google.ca/search?q=density+of+water&ie=utf-8&oe=utf-8&gws_rd=cr&ei=9TzLVur0FIjSjAO8866IAw

mine that ammonia, now ammonia gas (ammonia bils at -33.3C) from the atmosphere. Extract the hydrogen, expel the nitrogen. Use the hydrogen to combine with carbon for GHGs, or use it as rocket fuel.

22 hours ago, cantab said:

Callisto is probably the best bet because it at least doesn't need a radiation shield.

Regarding global warming potential, keep in mind it's defined based on Earth. Many gases are effective warmers on Earth because they "close the window", absorbing wavelengths that carbon dioxide and water vapour let through. Building an atmosphere from scratch the considerations will be different and a mixture of gases will be needed.

More direct, though, is a big lens or mirror in space. There may also be a significant contribution from the waste heat thrown off by whatever machinery is making the atmosphere.

The next question is what is the atmospheric escape like? "Jeans escape" is the loss of gas molecules that are travelling above the escape speed of the body they are on, and so if they are in the exosphere they fly off and never come back. On Earth it is very slow for anything but hydrogen and helium. But on Callisto, supposing an Earth-like exosphere temperature of 1000 K, it will be faster. The full formula is complicated, but it looks like Callisto would lose oxygen a thousand times faster than Earth loses hydrogen. So I think around 100 million tonnes a year will stream off into space.

Doing a little more maths, though, that is only about 1 millionth of the likely total mass of a Callistan atmosphere. So despite the atmosphere being totally unstable on geological timescales, if we can make it then keeping it "topped up" should be trivial.

Yeah, we probably need a casing, like for terraforming the moon- which would solve the GHG problem by the gas acting as a GHG.

[Spaceception]

27 minutes ago, AngelLestat said:

No sure why Titan has a 1.5bar atmosphere with lower gravity than Io, however this lost all its atmosphere in its orbit and then is sucked by jupiter magnetic fields.

that is what I said..  or no?

It's further away from the sun (And far away from Saturn), so its weak gravity can hold on to an atmosphere.

You did, I was speed-reading, so I didn't read it thoroughly the first time.

Edited February 22, 2016 by Spaceception

[fredinno]

9 hours ago, lajoswinkler said:

Ganymede has a higher surface gravity. It would help with the atmosphere retention. Ionizing radiation isn't that bad. 80 millisieverts per day is 4.16 microsieverts per hour. It's perfectly manageable (0.2 microsieverts per hour - that's my local dose here) and it will be orders of magnitude less if you're not tiptoeing through the tulips outside all the time and you mostly work inside.

Actually, no, Ganymede still needs a hull to keep the O2 N2 in if we want to keep it at Earth temperature- even though the gases are retented at current temperatures.

Ganymede is also ammonia deficient, so it will be have to be mined from Castillo- first warming it up by adding SH6, or CH4 (the former would be easiest due the the massive heating potential of it- it's the most effective GHG, but there is some CO2 on Ganymede and Castillo you can mine Carbon from for CH4.)

http://onlinelibrary.wiley.com/doi/10.1029/2002JE001956/pdf

It looks like ganymede may be marginally better.

[fredinno]

1 hour ago, AngelLestat said:

A thick atmosphere will reduce the radiation problem, and you need a really thick (full of greenhouse gases) atmosphere to provide some surface heat.
Water vapor is something that we can breath, but we need to prevent to form clouds or it will reflect the few sunlight we receive.
We need to search other greenhouses to help in this matter in a way that will not be toxic.
We can not solve the gravity problem, Io has the highest surface gravity, then the moon and other bodies.
So the only way to solve the gravity is with spinning habitats tilted, like a train habitat with tilted rails, the small difference in gravity between these moons does no really matter unless it helps to keep the atmosphere.
IO has internal heat that can be useful, no sure about its other resources.
 

 

1 hour ago, Spaceception said:

So if Io has an atmosphere about as thick as Earths. What would its RAD intake be, and what would its temperature be (Assuming it's mostly CO2)?

Also, Doesn't Io have the highest gravity of any Moon in the solar system?

 

27 minutes ago, AngelLestat said:

good point.

No sure why Titan has a 1.5bar atmosphere with lower gravity than Io, however this lost all its atmosphere in its orbit and then is sucked by jupiter magnetic fields.
But in any case, IO sulphur does not help, because combined with water reflect the light. (and there is no much water anyway).
I guess is no possible to terraform any of the bodies of the solar system without import elements from different places (no just the asteroids).

that is what I said..  or no?

Titan can hold its atmosphere because it is so much colder, so the N2 is less energetic than on the warmer Io. Radiation doesn't help. Hell, we could terraform Ganymede and make it like Titan relatively easily, methane seas and all, (but you have to bring the methane, or create it from mined Carbon and Hydrogen from elsewhere) Ganymede doesn't have those methane seas due to its formation around Jupiter being too hot for methane to precipitate.

Ganymede's current surface temperature and gravitation allows for us to make it a second Titan, much more easily than a fully terraformed Ganymede or Castillo

https://en.wikipedia.org/wiki/Methane

https://en.wikipedia.org/wiki/Ganymede_%28moon%29

26 minutes ago, sevenperforce said:

Someone should come up with a list of possible atmospheric compositions, temperatures, and pressures which are survivable for humans.

For example, is there anything other than nitrogen which will work as an inert gas? 

Yes, any inert gas, like the noble gases (except Radon and element 118, which are radioactive) will do. CO2 might even work, though then you'd have to sacrifice your Earth-like atmosphere, and wear O2 masks (CO2 will enter the blood stream and eventually kill you at very high concentrations), which would ruin the point of terraforming.

[sevenperforce]

14 minutes ago, fredinno said:

Yes, any inert gas, like the noble gases (except Radon and element 118, which are radioactive) will do. CO2 might even work, though then you'd have to sacrifice your Earth-like atmosphere, and wear O2 masks (CO2 will enter the blood stream and eventually kill you at very high concentrations), which would ruin the point of terraforming.

CO₂ will kill you even at relatively low concentrations. It's also an eye/mucus membrane irritant at high concentrations.

[KerikBalm]

On 2/21/2016 at 5:52 PM, Spaceception said:

Which Galilean moon would be best for Terraforming, and how? Btw, I'm not being strict, the atmosphere only needs to be thick enough so you don't need a pressure suit, and the temperature just needs to be high enough so you only need warm clothing (Winter clothing you'd wear in the pacific NW, and an oxygen mask.

Discuss, and please stay on the topic of Terraforming

 

As that graph above demonstrates: None.

None of the moons have a high enough escape velocity to hold on to atmosphere at any temperature that would be bearable with "winter clothing" at approximately 1 atmosphere.

On top of that... even if they could hold on to such an atmosphere, it wouldn't be warm.

Titan is the best you can hope for, and that atmosphere is nowhere near warm enough to go out with just a gas mask and some fur coats

[andrewas]

5 hours ago, fredinno said:

Yes, any inert gas, like the noble gases (except Radon and element 118, which are radioactive) will do. CO2 might even work, though then you'd have to sacrifice your Earth-like atmosphere, and wear O2 masks (CO2 will enter the blood stream and eventually kill you at very high concentrations), which would ruin the point of terraforming.

If you want to terraform a planet, you need nitrogen, plant life depends on it. If you just want to make it inhabitable by humans, you can get by with other gasses, and grow some crops by providing nitrates in the soil, but without natural nitrogen fixation there can never be wild plants.

[fredinno]

1 hour ago, andrewas said:

If you want to terraform a planet, you need nitrogen, plant life depends on it. If you just want to make it inhabitable by humans, you can get by with other gasses, and grow some crops by providing nitrates in the soil, but without natural nitrogen fixation there can never be wild plants.

Indeed, but you can always spray nitrates, then use modified bacteria to run the nitrogen cycle entirely without fixation, with all the nitrogen inthe cycle being recycled via decomposition. https://en.m.wikipedia.org/wiki/Nitrogen_cycle

[KerikBalm]

What sort of modifications do you suggest to the bacteria?

I see a lot of people throwing around genetic modification as if it willjust get around any problem.

Granted in this case of just nitrogen fixation on a unspecified planet isn't as bad as the earlier suggestion of "introducing genetically modified microbes to convert the atmosphere,"

Any microbes you send to the surface of any of those moons, are just going to die. There's not a genetic modification you can make to have them survive. The only place they might survive is in the liquid water mantle. The only liquid water mantles that are close to reachable are in Enceledus (no a Gallilean moon) or Europa.

None of the moons can support an atmosphere that would allow the bacteria to survive on the surface. The closest you could hope to terraforming would be to have the underwater environments somewhat resemble Earth's oceans. There's no environment that can be made for us there. To be very very generous... maybe an environment could be made where a deep sea invertebrate from Earth (like those that cluster aroun volcanic vents) could survive.

[fredinno]

1 hour ago, KerikBalm said:

What sort of modifications do you suggest to the bacteria?

I see a lot of people throwing around genetic modification as if it willjust get around any problem.

Granted in this case of just nitrogen fixation on a unspecified planet isn't as bad as the earlier suggestion of "introducing genetically modified microbes to convert the atmosphere,"

Any microbes you send to the surface of any of those moons, are just going to die. There's not a genetic modification you can make to have them survive. The only place they might survive is in the liquid water mantle. The only liquid water mantles that are close to reachable are in Enceledus (no a Gallilean moon) or Europa.

None of the moons can support an atmosphere that would allow the bacteria to survive on the surface. The closest you could hope to terraforming would be to have the underwater environments somewhat resemble Earth's oceans. There's no environment that can be made for us there. To be very very generous... maybe an environment could be made where a deep sea invertebrate from Earth (like those that cluster aroun volcanic vents) could survive.

No,I meant making it so that the nitrogen cycle is completely inside the soil, being recycled via decomposition.

[andrewas]

Is it possible to make it completely contained in the soil? Could we avoid all leakage to the atmosphere? And is it evolutionarily stable? It'd suck to set up this modified biosphere and find, in a thousand years, some bacterium has decided to dump nitrogen into the atmosphere. 

[sevenperforce]

I wouldn't be so sure about selling genetic modification short. Granted, gene modification is not as simple as dial-a-microbe, but it is pretty powerful. It's powerful because the range of extreme conditions under which how "wild" bacteria can survive is simply huge. Besides, you can splice genes in from different kingdoms, or create genetically modified fungi, or certain types of algae, or any other range of possible creatures. Earth's biodiversity is just simply gigantic as it is.

All you really need is to identify one biologically-active potential reaction, and then you can combine different species or even different kingdoms to create the chain you want. I'm thinking of something like a symbiotic yeast-bacteria colony...

Edited February 23, 2016 by sevenperforce

[fredinno]

3 hours ago, andrewas said:

Is it possible to make it completely contained in the soil? Could we avoid all leakage to the atmosphere? And is it evolutionarily stable? It'd suck to set up this modified biosphere and find, in a thousand years, some bacterium has decided to dump nitrogen into the atmosphere. 

Well, a terraformed moon woud need mainenance to be habitable already- and Ammonia feriliser is pretty common nowadays. It should be possible to spray nitrates every 1000 years while minimising leakage.

[Rakaydos]

On 2/21/2016 at 9:04 AM, peadar1987 said:

Callisto actually has the lowest dose rates:

Edit: I also read the full stop as a comma. There is an error in earth's value as well, it is ten times lower than shown here

 

Given an artificial atmosphere that perfectly converts ionizing readiation into thermal energy, how much heat would Europa and Ganamede receve from this radiation?

[peadar1987]

1 hour ago, Rakaydos said:

Given an artificial atmosphere that perfectly converts ionizing readiation into thermal energy, how much heat would Europa and Ganamede receve from this radiation?

Not much. A Sievert/second is a Watt per kg. Most of the energy hitting Europa is alpha and beta which doesn't pass through people, so a person on Europa's surface would be absorbing energy at a rate of maybe a couple of milliwatts. Unfortunately, the individual packets of energy are powerful enough to cause ionisation and DNA damage, so it doesn't take much total energy to seriously mess you up.

[Rakaydos]

Just now, peadar1987 said:

Not much. A Sievert/second is a Watt per kg. Most of the energy hitting Europa is alpha and beta which doesn't pass through people, so a person on Europa's surface would be absorbing energy at a rate of maybe a couple of milliwatts. Unfortunately, the individual packets of energy are powerful enough to cause ionisation and DNA damage, so it doesn't take much total energy to seriously mess you up.

Actually, I was talking about turning the hazardus radiation into benificial heat for the terriforming effort. I'm asing about the planetary warming made possible by turning the planet's entire atmosphere into a radiation absorber.