I Terraforming Mars by using Europa

[James Minwell]

Hi,
Do you think there is any feasibility at all to terraform Mars be crashing Europa into it? Of course, you have the near impossible task of knocking Europa out of Jupiter's orbit and guiding into Mars without ruining its orbit...but if it worked maybe this would give Mars the extra mass, heat and water to sustain life (after 1,000 years or so) Thanks! or also maybe guiding asteroid to fly by Venus to help expel enough of its thick atmosphere to help terraform it?
Thanks!

 

[mfb]

The impact would melt the Martian surface and spread debris all over the inner solar system, which leads to many large impacts on Earth. I don't think that is a good idea.

The additional mass for Mars would be negligible. The additional water, after the surface cooled down sufficiently (that will take a long time), would be sufficient to cover all of Mars with an ocean with an average depth of 20 km. Olympus Mons might still be above the ocean.

Even if we ignore the logistics of the impact, I'm not sure if the result would be good. Why not deliver some of the water without the rest of the moon?

Mars still has a lot of water. It is just frozen at the moment.

 

[infinitebubble]

Terraforming Mars is useless until a magnetic shield to protect it from the Sun and it's effects are in place... much better than slamming a Jupiter satellite onto Mars which is an engineering feat we could never do.

https://www.space.com/31044-mars-terraforming-nasa-maven-mission.html

https://www.nasa.gov/feature/goddar...otect-astronauts-from-space-radiation-on-mars

 

[mfb]

Even without magnetic field, atmospheric losses would be small, and only relevant over millions of years. Way beyond the planning horizon we have today. We don't have to solve 40,000th century problems with 21st century ideas.

 

[James Minwell]

maybe with all that water it would drastically reduce the time needed to cool and additionally burn off a lot of that water so it wouldn't so flooded. or how about Venus? any way to reduce the thick atmosphere?

 

[mfb]

The impact energy would correspond to the energy Mars receives from the Sun in about 1 million years.
Sure, some water would escape, but probably not much, and water vapor is a very good greenhouse gas - it would slow down cooling.

or how about Venus? any way to reduce the thick atmosphere?

There are some ideas how to remove most of the CO2, but they are very speculative.

 

[Sherwood Botsford]

A linear accelerator (railgun) on the surface of Europa hurling 10 kg hunks of ice at Mars would be a better way: Would either vaporize when they hit atmosphere, or churn up some crust on impact. In either case the water ends up in the atmosphere as a greenhouse gas.

Magnetic field: It would take 250,000,000 A in a superconducting ring around the equator of Mars to generate a 1/2 gauss field. Yeah. Quibble about the geometry.

This is a small project compared to moving Europa.

 

[Daytah]

Terraforming Mars is useless until a magnetic shield to protect it from the Sun and it's effects are in place... much better than slamming a Jupiter satellite onto Mars which is an engineering feat we could never do.

https://www.space.com/31044-mars-terraforming-nasa-maven-mission.html

https://www.nasa.gov/feature/goddar...otect-astronauts-from-space-radiation-on-mars

Was wondering when someone would notice. Big surprise!
Daytah

 

[Sherwood Botsford]

I'm hesitant about saying 'never' when talking about engineering. In 1700 landing on the moon was a 'never' job.

While moving moons is beyond my current view of present and future technology, moving comets out of the Oort cloud is not.

***
Smashing Europa into Mars even if done at minimum velocity is likely to splash enough rocks that the whole inner solar system becomes a riskier place.

OTOH, firing off 10 Kg ice cubes (pick a size that will vaporize in the atmosphere) may be a way both to make Mars wet again, and to warm it up. Something like a rail gun with a resuable bucket, as Stine proposed for moving lunar rock to a Lagrange point in "The Third Industrial Revolution" A cubic km of water weighs a billion kg. 33 kg / second sends a km^3 per year.

 

[stefan r]

Hi,
Do you think there is any feasibility at all to terraform Mars be crashing Europa into it? Of course, you have the near impossible task of knocking Europa out of Jupiter's orbit and guiding into Mars without ruining its orbit...but if it worked maybe this would give Mars the extra mass, heat and water to sustain life (after 1,000 years or so) Thanks! or also maybe guiding asteroid to fly by Venus to help expel enough of its thick atmosphere to help terraform it?
Thanks!

Why Europa. Ceres is much closer to Mars and is not inside of Jupiter's gravity well. An object orbiting outside of Neptune's orbit would take much less energy to move into a more elliptical orbit. You could time perihelion so that one of the gas giants pulls an object into a lower or more elliptical orbit which intersects Mars orbit.

... if it worked maybe this would give Mars the extra mass, heat and water to sustain life (after 1,000 years or so)

Building a space habitat with larger surface area than Mars would take significantly less energy. Would be available for occupation when completed and could be completed in a sequence of smaller pieces.

... also maybe guiding asteroid to fly by Venus to help expel enough of its thick atmosphere to help terraform it?
Thanks!

I don not see how asteroid flybys will help remove Venus's atmosphere. If you expend the energy and effort lifting CO₂ off of Venus why not use it? Carbon fiber objects can be manufactured using less energy than is required to lift the carbon off of Venus. Carbon is scarce on Mercury and on Earth's moon.

Breathable air floats in CO2 the way helium floats in Earth's atmosphere. If you feel strongly that someone should occupy Venus you could put them in a dirigible or balloon. There are difficulties with that idea but removing the atmosphere is very difficult. Venus poses some geology problems. Venus's rotation is so slow that with a thinner atmosphere the surface temperature would go through extreme swings.

...OTOH, firing off 10 Kg ice cubes (pick a size that will vaporize in the atmosphere) may be a way both to make Mars wet again, and to warm it up. Something like a rail gun with a resuable bucket, as Stine proposed for moving lunar rock to a Lagrange point in "The Third Industrial Revolution" A cubic km of water weighs a billion kg. 33 kg / second sends a km^3 per year.

A 10 kg ice cube would sublime in the vacuum of space. Free water molecules would interact with the solar wind and most (all?) of it would miss Mars.

 

[mfb]

A 10 kg ice cube would sublime in the vacuum of space. Free water molecules would interact with the solar wind and most (all?) of it would miss Mars.

Let's see. We start with a liter-sized sphere of ice (easier to calculate later), let's say we want to keep evaporation below 1 cm of surface layer to keep most ice. Here is a model. Sublimation will only be interesting closer to Mars where the block of ice is warmer, let's take 1 year = 10000 hours with relevant sublimation. To stay below 1g/cm², we need a temperature below 165 K. Note the extremely logarithmic scale: The temperature we need doesn't change much if we change the evaporation rate a lot. Let's take 160 K, that gives an additional safety factor of ~3.

What is the albedo of our ice? This website suggests 0.73 in the visible light and 0.33 in the near infrared for "bare non-melting sea ice thicker than 0.5 m". I'll assume 0.6 for sunlight here, should be conservative. Emission should be close to a perfect blackbody. Then our sphere has an equilibrium given by $\displaystyle 0.4 \frac{L_{sun}}{4 \pi R^2} \pi r^2 = 4 \pi r^2 \sigma T^4$ where the radius r of the ice cancels out. Simplified: $\frac{L_{sun}}{ 40 \pi T^4 \sigma} = R^2$. Plugging in T=160 K leads to R=1.9 AU. Mars is at 1.38-1.67 AU. Solving in reverse, we get 180 K, or an evaporation rate that is a factor ~20 larger. This evaporation rate will only be reached very close to Mars, however. We can also aim for Mars' aphelion, at 172 K we are very close to the original target of 165 K.

If this calculation is accurate (I doubt it), then sending kg to ton-scale objects might work. Evaporation and its effect on the trajectory should be quite predictable.

This does not take solar wind or similar effects into account.

 

[stefan r]

Let's see. We start with a liter-sized sphere of ice (easier to calculate later), let's say we want to keep evaporation below 1 cm of surface layer to keep most ice...

If this calculation is accurate (I doubt it), then sending kg to ton-scale objects might work. Evaporation and its effect on the trajectory should be quite predictable...

We could bag the ice. Then we just need vapor pressure to be below the pressure that pops the bag. Polyethylene contains hydrogen too.

A linear accelerator (railgun) on the surface of Europa hurling 10 kg hunks of ice at Mars would be a better way...

This is a small project compared to moving Europa.

Anyone know how 1,000,000 rail guns shooting 10 kg compare to 1000 shooting 10 tons and 1 shooting 10,000 tons? The only detailed descriptions I have read assumed an Earth based launch. Most also assume a human or sensitive instruments in the payload.

If the rail is on the surface (or in, under, and out of) how often is a launch window open? How many degrees spread can we get adjusting the velocity and still hit Mars? Could you launch toward Jupiter or away to get 2 windows?

If they launched 1 projectile with 9,990 tons of ice and a 10 ton rocket vehicle with sun shield/solar array they could correct the aim in route to Mars. They could electrolyze some ice to make H₂LOx fuel. A rocket burn close to Mars would still dump most the hydrogen into Mars' gravity. So the shuttle would disconnect from the ice ball and fly back to Europa.

A hydrogen tank might work out better.

Should be easier to shoot ammonia Ice from Callisto than water ice from Europa. Ammonia has more Hydrogen per kilo. Callisto has water too. Just getting Mars wet does not recreate an Earth like atmosphere.

 

[Tryannosaurus]

Most of these ideas seem to require more advanced technology than we have today and some don't have the practicality to actually work, like rail guns, you'd need quite a lot of rail guns shooting 10 KG of ice to warm and make Mars wet again. You'd have to get there and assemble the thing, not counting the resources you'd have to spend building all those rail guns. This project would be a logistical disaster. By the time we'd be capable of doing this in a short amount of time, terraforming Mars would be a piece of cake. The original idea of crashing Europa into Mars is even more impractical.

Why couldn't we just build a machine that freezes salt water from our oceans and a rail gun that shoots this frozen salt water? We could actually have a use for our ocean water that mostly gets unused, much more practical than shooting ice from Europa

 

[mfb]

Shooting things through an atmosphere is very difficult. And while it would slow down the sea level rise a bit if done on a terraforming scale, I think most people would like to keep the water here.

Installing a railgun on a moon is orders of magnitude easier than moving the moon.

 

[Tryannosaurus]

Shooting things through an atmosphere is very difficult. And while it would slow down the sea level rise a bit if done on a terraforming scale, I think most people would like to keep the water here.

Installing a railgun on a moon is orders of magnitude easier than moving the moon.

Surely shooting ocean water on to Mars won't do deplete our plentiful supply of it, also it's ocean water, no one cares about it too much, if we were to shoot fresh water there'd be a problem. Also you wouldn't have to literally shoot our entire ocean over to Mars, just enough so the ice caps melt and warm the planet.

On the bright side it'll "reverse" all the damage done to the sea level in the past years and even decrease sea levels before the Industrial Revolution. Gigantic amounts of sea water don't have to be sent over to Mars as Mars has frozen water at its poles anyways.

I think it's a feasible way of terraforming Mars over a period of time. We'd just need a strong enough cannon to shoot ice at escape velocity without it melting in the atmosphere. Another solution could be to make a orbital station that gets supplied with frozen sea water. This station could include a lot of cannons which wouldn't have to be as powerful as they would be on the ground. Much less energy would be needed to shoot the payload. The method of supplying the station could be thought of later like how the ISS is supplied

 

[mfb]

Surely shooting ocean water on to Mars won't do deplete our plentiful supply of it, also it's ocean water, no one cares about it too much

Mars' surface area is 1/3 the surface area of Earth's oceans. If you want to shoot 1 million km³ of water there, about 1/3 the water in the Martian ice caps, enough for a 9 m layer of water on Mars, you would reduce the ocean levels by 3 meters. That would make a lot of people very unhappy.

If you just want the impact to heat Mars, there is no need to use water, every random asteroid will do the job as well.

 

[Tryannosaurus]

Mars' surface area is 1/3 the surface area of Earth's oceans. If you want to shoot 1 million km³ of water there, about 1/3 the water in the Martian ice caps, enough for a 9 m layer of water on Mars, you would reduce the ocean levels by 3 meters. That would make a lot of people very unhappy.

If you just want the impact to heat Mars, there is no need to use water, every random asteroid will do the job as well.

A 3 metre drop in sea level might be a little troublesome for people but this is a small matter compared to the terraforming of Mars, a feet mankind has never accomplished before, if people don't sacrifice something to gain something else we'll never progress. The 3 metre reduction in sea levels may introduce more land to the planet and helping to reduce over population. The benefits far out weight the side effects of 3 metre reduction in sea levels

 

[mfb]

A 3 metre drop in sea level might be a little troublesome for people

A little troublesome? If we had this drop now and suddenly it would probably start an unprecedented recession and maybe even wide-spread famine because large parts of the global trade would stop working. If you can anticipate it you can dig every harbor deeper, but that would be a giant project on its own.

Sure, you can, but as I said: Many people wouldn't be happy about it. And where is the point? There is so much water available elsewhere.

 

[Tryannosaurus]

A little troublesome? If we had this drop now and suddenly it would probably start an unprecedented recession and maybe even wide-spread famine because large parts of the global trade would stop working. If you can anticipate it you can dig every harbor deeper, but that would be a giant project on its own.

Sure, you can, but as I said: Many people wouldn't be happy about it. And where is the point? There is so much water available elsewhere.

As of right now you've already anticipated that sea levels would drop, so a huge project of digging the most important harbors essential to global trade routes deeper wouldn't be too hard even with our current technology, the hardest part would be to fund the project, but logistics and funding can be worried about later as that's too complicated. We could start digging our main harbors deeper while the station or whatever platform we're shooting from is being built. Our planet is the closest planet that contains water to Mars, it would be much faster getting our water and shooting it to Mars than it would be say a distant frozen Moon like Europa. And on Earth the project would be much more controlled due to the ease of access to it, if something went wrong we could fix it much faster than if it were elsewhere.

Returning back to my solution to your predicament, digging the main harbours such as Singapore, Hong Kong, Dubai and all the large ports essential to trade routes. This would still allow for global trading to be possible, even though smaller ports will be dug deeper later, the trading system of the world won't be hurt too badly. What's stopping us from doing a big project? Funds? Let's forget about that.

Though I do agree there would need to be a lot of planning involved in executing two gigantic global projects side by side. But what's stopped mankind from doing these large feets? Might as well try...

 

[mfb]

Our planet is the closest planet that contains water to Mars

Mars has water.

Shooting through the atmosphere is very difficult, evaporation would be a huge issue at 1 AU, and the moons of Jupiter have a much lower escape velocity.

Returning back to my solution to your predicament, digging the main harbours such as Singapore, Hong Kong, Dubai and all the large ports essential to trade routes. This would still allow for global trading to be possible, even though smaller ports will be dug deeper later, the trading system of the world won't be hurt too badly.

This would never fly simply for political reasons even if it wouldn't cost any money.

 

[Tryannosaurus]

Mars has water.

Shooting through the atmosphere is very difficult, evaporation would be a huge issue at 1 AU, and the moons of Jupiter have a much lower escape velocity.This would never fly simply for political reasons even if it wouldn't cost any money.

The in atmosphere energy needed for shooting can be ignored if we use the method I propose of having a orbital platform to shoot from, no need to shoot from the surface of Earth, either that or establish a Moon station to shoot from. Establishing a station in the Moon wouldn't only help to terraform Mars, we could use that as a base to mine the Moons resource rich surface, containing elements not usually found on Earth, such as Helium-3, we could get two birds with one stone, as Helium-3 can be used in nuclear fusion, which if scientists figure out how to control the super heated plasma, could completely solve our issue of climate change.

And I try to avoid politics in these debates as they ruin many many ideas that could be plausible without it, but I guess it's unavoidable. It's nice to theorise things like this without issues such as logistics, funding and politics as they require a lot of re analysing

 

[mfb]

The in atmosphere energy needed for shooting can be ignored if we use the method I propose of having a orbital platform to shoot from

You still have to get the water to the platform. Installing a railgun and solar cells on one of Jupiter's moons sounds easier.

Helium-3 fusion processes are harder than DT fusion, and DT fusion is sufficient to satisfy every foreseeable energy demand.

 

[Tryannosaurus]

You still have to get the water to the platform. Installing a railgun and solar cells on one of Jupiter's moons sounds easier.

Helium-3 fusion processes are harder than DT fusion, and DT fusion is sufficient to satisfy every foreseeable energy demand.

It may sound easier but if you look into practicality, you'd have to assemble the rail gun at the Europa robotically, and maintenance of the rail gun would be near impossible, if something went wrong there would be no way to fix it. Having one on the Moon or orbiting Earth would be much easier to maintain and take control of.

 

[litup]

Terraforming Mars is useless until a magnetic shield to protect it from the Sun and it's effects are in place... much better than slamming a Jupiter satellite onto Mars which is an engineering feat we could never do.

https://www.space.com/31044-mars-terraforming-nasa-maven-mission.html

https://www.nasa.gov/feature/goddar...otect-astronauts-from-space-radiation-on-mars

That problem will go away if and when we find room temp superconductors, I calculated 4 turns of super wire wrapped around the equator and fed with about 50,000 amps will generate a field about equal to Earth's. And the nice thing is the current lasts for a long time, at least till the field gets attacked by solar flares, I imagine that would suck out some current and require replacing but it would work. So it just comes down to superconductor development and engineering. I imagine it would work with just 100 degree K stuff we have now also but would require a massive refrig system taking a LOT of energy to maintain.

I see I am not the only one to think of superconductor rings on Mars but my calcs show a lot lower current needed for multiple turn loops.

 

[stefan r]

...Our planet is the closest planet that contains water to Mars, it would be much faster getting our water and shooting it to Mars than it would be say a distant frozen Moon like Europa. And on Earth the project would be much more controlled due to the ease of access to it, if something went wrong we could fix it much faster than if it were elsewhere...

What "close" means is a bit weird in a solar system where everything is rotating. Should at least check delta V. On this map it shows Earth to Mars 12.16 km/s and Europa to Earth 6.86 km/s (Europa Mars a bit easier). Ceres to Earth transfer is only 4.37 km/s.

The absurd plan assumes a launch complex capable of firing a cubic km or ice. Things could go horribly wrong with thousands of units but the construction crews will still be working on hundreds of thousands more at the site. So repairs and upgrades could be a minor inconvenience. Removing a small part the surface of a planet or moon is a far larger infrastructure than we have in place on Earth today.

 

[nikkkom]

What is technically feasible in foreseeable future (a few ~100s of years) is nudging some long-period comets which already pass near Mars, into colliding with it. The necessary dV to adjust orbits is small if you do it far away from perihelion, say at something like Neptune's distance from Sun.

To reduce damage to Mars, a very oblique entry into atmosphere may be best. Also, mining into the comet and putting in a several megaton fusion bomb(s) would allow you a controlled disintegration at a controlled altitude in Mars atmosphere. Another possibility worth looking into is aerocapture of the comet into a Mars orbit, and gradual dismantling (however I have doubts it can survive g forces intact).

 

[litup]

What is technically feasible in foreseeable future (a few ~100s of years) is nudging some long-period comets which already pass near Mars, into colliding with it. The necessary dV to adjust orbits is small if you do it far away from perihelion, say at something like Neptune's distance from Sun.

To reduce damage to Mars, a very oblique entry into atmosphere may be best. Also, mining into the comet and putting in a several megaton fusion bomb(s) would allow you a controlled disintegration at a controlled altitude in Mars atmosphere. Another possibility worth looking into is aerocapture of the comet into a Mars orbit, and gradual dismantling (however I have doubts it can survive g forces intact).

If it didn't survive g forces there would still be smaller chunks that could be de-orbited and anyway, I would think if something of that magnitude was to be done, it would be done before humans arrive so nobody would get hurt.

There still would be an ethical issue to deal with: We don't know if there is life there, but if there is, and we start slamming down comets raining destruction of the hypothetical eco-system, could we ethically do that to life on another planet in our zeal to terraform Mars?

 

[mfb]

in foreseeable future (a few ~100s of years)

Do you think people in 1800 could foresee how our world looks today?
I expect the world to change much more in the next 200 years than it did in the previous 200 years.

I would think if something of that magnitude was to be done, it would be done before humans arrive so nobody would get hurt.

We will probably have the technology to go to Mars within 20 years. Deflecting comets will take longer.

Concerning possible life on Mars: That is actively studied.

 

[nikkkom]

There still would be an ethical issue to deal with: We don't know if there is life there, but if there is, and we start slamming down comets raining destruction of the hypothetical eco-system, could we ethically do that to life on another planet in our zeal to terraform Mars?

I don't have ethical issues with killing bacteria and such. I brush my teeth every day :D

Cordoning off Mars forever just because there might be some bacteria is completely unreasonable decision on cost/benefit metrics. However, I fully expect that enviro-nuts will promptly go off the rails on this issue and label anyone who disagrees with them "murderous fascists hell bent on exterminating poor oppressed Martian bacteria" and such.

 

[mfb]

I don't have ethical issues with killing bacteria and such. I brush my teeth every day :D

Cordoning off Mars forever just because there might be some bacteria is completely unreasonable decision on cost/benefit metrics. However, I fully expect that enviro-nuts will promptly go off the rails on this issue and label anyone who disagrees with them "murderous fascists hell bent on exterminating poor oppressed Martian bacteria" and such.

Even if you completely ignore ethical questions (and I don't think you should), there are huge scientific and even economic benefits of studying very foreign life - we would learn much more about life in general.

 

[nikkkom]

Sure. But nothing prevents studying Martian life while Mars colonization is underway. It's certain to be different enough from Earth bacteria so that "contamination" of Earth origin should not be a huge problem for analysis. Real-world example: Genesis' spacecraft crashed on landing and contaminated its samples with Earth materials, however analysis was still largely successful.

 

[Tryannosaurus]

Surely crashing a few puny comets to the surface of Mars would do nothing to the so called bacteria living on Mars, if there is life on Mars then it would need to have adapted to the harsh Martian climate and solar flares and other cosmic events, dust storms, high carbon dioxide levels and such, a few comets crashing would be the least of their worries...

 

[litup]

Surely crashing a few puny comets to the surface of Mars would do nothing to the so called bacteria living on Mars, if there is life on Mars then it would need to have adapted to the harsh Martian climate and solar flares and other cosmic events, dust storms, high carbon dioxide levels and such, a few comets crashing would be the least of their worries...

But what if we found surviving pockets of higher life forms, squidy things in a buried lake or hydrovent?

 

[stefan r]

Surely crashing a few puny comets to the surface of Mars would do nothing to the so called bacteria living on Mars, if there is life on Mars then it would need to have adapted to the harsh Martian climate and solar flares and other cosmic events, dust storms, high carbon dioxide levels and such, a few comets crashing would be the least of their worries...

The less it effects the climate the more useless the action.

Plants on Earth evolved to grow in shade usually die when they get too much sun. Desert plants tend to develop root rot when you water them. Tundra will not grow in the tropics, tropical plants die when leaves freeze. Climate change is highly disruptive and makes it very difficult to study what the ecology was like before disruption.

Any organism starves if some other organism eats its food. Organisms die when they are eaten. Few organisms that are adapted to a martian atmosphere would be able to survive for long in a Earth atmosphere. The likelihood of competing against organisms that are adapted comes close to zero.

 

[rootone]

Getting several billion tonnes of water off of Earth would require several billion tonnes of rocket fuel, and a fleet of rockets numbering several thousands.

 

[mfb]

Why would you launch this with rockets? There are better ways to get huge amounts of matter into orbit or beyond. They are not worth the investment today, but with larger demand they would be built.

 

[stefan r]

Getting several billion tonnes of water off of Earth would require several billion tonnes of rocket fuel, and a fleet of rockets numbering several thousands.

Would be impressive rocket if it can lift a million tons. Space shuttle could launch almost 4 tons to GEO. The shuttle program launch 134 times.

Lifting water off Earth is much harder than Ceres, Europa or a lot of comets.

Pluto-Charon may have been demoted from planet status but there is lots of water and nitrogen.

 

[DET]

Terraforming Mars is useless until a magnetic shield to protect it from the Sun and it's effects are in place... much better than slamming a Jupiter satellite onto Mars which is an engineering feat we could never do.

https://www.space.com/31044-mars-terraforming-nasa-maven-mission.html

https://www.nasa.gov/feature/goddar...otect-astronauts-from-space-radiation-on-mars

Has anyone ever come up with an even semi-plausible method of restarting Mars' magnetic field?

 

[rootone]

Has anyone ever come up with an even semi-plausible method of restarting Mars' magnetic field?

Assuming we understand the mechanism for Earth's magnetic field correctly, the method would need to create something similar for Mars..
That is we would need to liquify the core then spin it up.
It doesn't break any laws of physics but the amount of energy involved would be enormous, and certainly well beyond any present technology.

 

[Jon Richfield]

Most of these ideas seem to require more advanced technology than we have today and some don't have the practicality to actually work, like rail guns, you'd need quite a lot of rail guns shooting 10 KG of ice to warm and make Mars wet again...
...

Why couldn't we just build a machine that freezes salt water from our oceans and a rail gun that shoots this frozen salt water? We could actually have a use for our ocean water that mostly gets unused, much more practical than shooting ice from Europa

IMO when terraforming Mars (as opposed to more promising options like Venus and Mercury say, or colonising spacecraft or asteroids) is discussed, religious rage takes over where rationality leaves off.

All quite unnecessary really; freezing water from Earth's oceans and shooting the ice to Mars indeed! As someone pointed out, pointed out, parts of Mars have large quantities of brine, even in comparison to some parts of the Atacama desert. All the colonists need do is install a few open-cast frozen-brine mines and power generators, and brine desalination plants, and Robert is your mother's brother. Of course, grabbing a bit of H2, NH3, and CH4 from Jupiter and various moons would be equally easy.

Mars will be ours, and flushing green around our colonial cities.

Or something...

 

[DET]

Assuming we understand the mechanism for Earth's magnetic field correctly, the method would need to create something similar for Mars..
That is we would need to liquify the core then spin it up.
It doesn't break any laws of physics but the amount of energy involved would be enormous, and certainly well beyond any present technology.

Looking at the earlier suggestion to put a superconducting ring around Mars -- would that not gradually heat the core through hysteresis, for instance? Granted, the time scale would be ridiculous. But maybe multiple lines of attack? Superconductiong ring providing inductive heating, plus H-bombs dropped down a deep shaft, plus microwave energy being beamed to the poles and used in some kind of either heating or further induction...

I'm just spitballing, and I freely admit I haven't a clue.

 

[mfb]

The global thermonuclear arsenal is about 6*10¹⁸ J (number from here), divided by the mass of Mars we get 10 µJ/kg. If you somehow manage to heat 10% of Mars only you get 0.1 mJ/kg. Utterly negligible.

As comparison: It is about the energy Mars receives as sunlight every 10 seconds.

 

[stefan r]

Looking at the earlier suggestion to put a superconducting ring around Mars -- would that not gradually heat the core through hysteresis, for instance? Granted, the time scale would be ridiculous. But maybe multiple lines of attack? Superconductiong ring providing inductive heating, plus H-bombs dropped down a deep shaft, plus microwave energy being beamed to the poles and used in some kind of either heating or further induction...

I'm just spitballing, and I freely admit I haven't a clue.

If you build huge superconducting rings why would you heat Mars' core? Would already be a huge magnet.

The only reason to bother with the magnet is to avoid some of the ionizing radiation. Detonating nuclear bombs is not a way to reduce exposure to ionizing radiation.

Microwaves are usually considered safe radiation but microwaves do not penetrate. You will only get convective flow if the inside is hotter than the outside.

 

[Sharky1]

I like the idea of sending some of Earth's ocean water to Mars. I'm not sure about railguns and the like though.
I assume by the time we are ready for anything even remotely close to this we should have an operating space tether/elevator.
Could it even be possible in the future to siphon the ocean water up through the middle of a space tether and send it on to Mars from there? Once in space and frozen you could then shoot it to Mars however you like.
Probably need multiple space tethers to keep the weight down too.

 

[stefan r]

...
Could it even be possible in the future to siphon the ocean water up through the middle of a space tether and send it on to Mars from there? Once in space and frozen you could then shoot it to Mars however you like.
Probably need multiple space tethers to keep the weight down too.

Hydrogen is much lighter than water. Methane is also lighter and can easily be converted to water on other planets. I have doubts about the friction on 40 million meters of pipe. One large pipe will transport more fluid without bursting. A space tether pipe material would have to be much stronger than a space tether material because internal pressure adds stress.

Materials that exist could build an elevator on Europa, Ceres, or a bridge from Pluto to Charon.

You might like the space fountain idea. If hydrogen ions or molecules are the particle stream then you could collect some in space instead of sending them back down.

 

[Tryannosaurus]

I like the idea of sending some of Earth's ocean water to Mars. I'm not sure about railguns and the like though.
I assume by the time we are ready for anything even remotely close to this we should have an operating space tether/elevator.
Could it even be possible in the future to siphon the ocean water up through the middle of a space tether and send it on to Mars from there? Once in space and frozen you could then shoot it to Mars however you like.
Probably need multiple space tethers to keep the weight down too.

Finally someone who understands me, by the time we got through political trouble and annoyances on Earth, we'd most likely have the technology to have a space elevator sort of contraption or a way to siphon water up to a planetary space station or at least a Moon base, firing frozen water from the Moon is MUCH easier than from Earth due to the Moon having negligible, but building a space tether to Mars may be out of reach for quite a while, that's not counting it being worth it or not, by the time the construction was completed we'd probably have been able to cover Mars with water

But why terraform Mars when even if it had water would still be relatively uninhabitable? I mean if Mars lost its magnetic field once, who's to say it will lose it again once we resort it? Unless we made the magnetic field nearly as strong as Earth's, the magnetic field would most likely be lost. Also the fact that Mar's atmosphere is basically carbon dioxide might make it a little hard to breath in don't you think?

 

[mfb]

We cannot restore the magnetic field of Mars. We don't have to do so either.

Also the fact that Mar's atmosphere is basically carbon dioxide might make it a little hard to breath in don't you think?

Getting some oxygen into the atmosphere is easier than large amounts of water.

 

[stefan r]

...by the time we got through political trouble and annoyances on Earth, we'd most likely have the technology to have a space elevator sort of contraption or a way to siphon water up to a planetary space station

I believe the space elevator is a materials science problem. What political opposition do you know of?

...firing frozen water from the Moon is MUCH easier than from Earth due to the Moon having negligible, but ...

Water is in short supply on the moon. Highly unlikely that any lunar water will be fired to Mars. It is possible that rockets traveling to Mars will burn fuel collected on the moon. Rocket fuel would not add any water to Mars' surface.

If you mean lifting water from Earth to the Moon and then relaunching to Mars then no it is not easier. A direct shot would be much lower energy. Flying past the moon for a gravity assist could help.

a space tether to Mars may be out of reach for quite a while, that's not counting it being worth it or not, by the time the construction was completed we'd probably have been able to cover Mars with water

The mass of a Mars skyhook attached to Phobos would be much lower than the mass of an ocean. A cubic kilometer of water would not be an ocean. A million tons of water compared to 10,000 tons of materials. Most of the material for the Phobos skyhook could be acquired on Mars and likely on Phobos.

...
But why terraform Mars when even if it had water would still be relatively uninhabitable? I mean if Mars lost its magnetic field once, who's to say it will lose it again once we resort it? Unless we made the magnetic field nearly as strong as Earth's, the magnetic field would most likely be lost. Also the fact that Mar's atmosphere is basically carbon dioxide might make it a little hard to breath in don't you think?

Removing the CO2 would be much easier than bringing in Nitrogen. The pressure is less than 1% of Earth's atmosphere. Ejecting carbon into space from Mars would be the same energy scale as escaping Jupiter's gravity from Europa. Depositing coal would be much lower energy and mechanically easier. Overall may be more than 1000x less effort. Terraforming would also include adding plants which need the CO₂ so removing would be counter productive.

Of course Europa is short on Nitrogen. But we can repeat this nonsense using Titan instead.

 

[mfb]

Phobos has a mass of 10¹⁶ kg. You are fine with moving that to a significantly higher orbit (and probably moving Deimos as well, another 1.5*10¹⁵ kg), but you are worried about 10¹² kg for a cubic kilometer of water?

10¹⁶ kg of water, corresponding to the mass of Phobos, could give Mars a uniform 7 cm layer of water. Or many reasonably sized lakes in many interesting places.

 

[stefan r]

Phobos has a mass of 10¹⁶ kg. You are fine with moving that to a significantly higher orbit (and probably moving Deimos as well, another 1.5*10¹⁵ kg), but you are worried about 10¹² kg for a cubic kilometer of water?

10¹⁶ kg of water, corresponding to the mass of Phobos, could give Mars a uniform 7 cm layer of water. Or many reasonably sized lakes in many interesting places.

My first thought when I read that was "I said skyhook not elevator". A skyhook hanging off of Phobos does not require any moving of Phobos.

Then I looked at the numbers. Going from Phobos to Deimos takes 745 m/s delta v. I believe that figure includes take off and landing. Is also overkill for anything in between including geosynchronous (areosynchronous?) . Delta V launching from Earth's surface to low Earth orbit is around 9,000 m/s.
9000/745 = 12

Tsoilkovsky rocket equation:
Δv = v_exh ln(m₀/m_f)
or
m0/mf=e^(Δv/v)
To get 12 times the delta V the mass ratio needs to increase by e¹² which = 1.7 x 10⁵ So order of magnitude estimate the 1 km³ of water takes 10x more fuel even if just moving to LEO. The starting mass and final mass need to include rocket engines and tanks which could be worse for the water lift. Phobos is not made out of rocket fuel so it is not that simple. But if you have a large cable you can catapult material and plug it into the Tsoilkovsky equation.

Maybe you could also use a tether to catch and de-orbit the ice from Europa. I am inclined toward thinking Phobos is well placed right where it is now. :)