Submitted by Pornelius_McSucc t3_113l5ul in space
Pornelius_McSucc OP t1_j8r4c9t wrote
Reply to comment by zolikk in Terraforming a magnetosphere possible? by Pornelius_McSucc
Well the biggest reason I can see, is that energy is finite in our solar system and artificial methods would take a lot. If we made some system to harness the sun's energy like a dyson swarm it could make it possible on a planetary scale, but it's a close margin otherwise with nuclear energy. You're right as far as everything else goes, an artificial field is more practical and less of an undertaking.
zolikk t1_j8r5syc wrote
Of course all this depends on what "level" civilization we are assuming, i.e. how much energy and what ability to move resources at large scale there are.
To just terraform the surface of Mars we don't need so much. Of course it's huge compared to what we can do now, but it's nowhere near dyson swarm capability levels. Technically it's probably enough to just dump a lot of atmosphere (lots of oxygen of course) plus water (from small icy asteroids e.g.) onto Mars; once it has a thick enough atmosphere with enough water vapor it will warm up through greenhouse effect.
No need for a magnetosphere.
If you still wanted one, even an artificial one, that would take a bit more effort. Not a big deal for a type II civilization, but still you do not need to wait until then to terraform Mars. You can just terraform it the "easy" way as above, even if it's not permanent you don't care, and then you might "fix it" later when you've advanced more - if you even care about it at that point.
To be honest I don't think any self-respecting type II civ would bother with a dyson swarm. That was conceptualized before the notion of nuclear energy was even mainstream understanding. If you're on that level of energy harnessing, using a dyson swarm is pointless; the Sun is an absolutely terrible "fusion reactor". You would instead use artificial fusion yourself. Would take fewer resources than a dyson swarm, you could create as much power as you want (easily more than the Sun itself, even if you just use fuel from Jupiter and leave the Sun alone as a token "natural reserve") and it would be a concentrated, on-demand power source. Of course at this point a project like "terraforming Mars" would become like a school science project.
Pornelius_McSucc OP t1_j8r66kb wrote
I thought the absence of a magnetosphere basically equates to the planet's surface being sterilized, and the UV rays from Sol fuck with essential compounds in a bad way. The dyson swarm being an obsolete concept is interesting, I appreciate knowing that now.
zolikk t1_j8r77xq wrote
I don't think it's in any way critical to that. Those kinds of harmful waves, from UV to gamma, are mainly helped by having a thick enough atmosphere - its exact composition can matter too though (mainly for UV absorption). But initially all this requires is just dumping a lot of gas of your desired makeup onto Mars. The medium term stability of that atmosphere depends mainly on chemical (and eventually biologically driven) reactions near the surface...
Mars has weaker gravity so it won't be able to help hold onto the thick atmosphere long term. This is where a magnetosphere helps, because it can protect molecules in the upper atmosphere from being ejected by solar rays when in normal conditions they wouldn't reach escape velocity. But Mars' gravity is too low anyway, even with a magnetosphere it wouldn't be able to hold an Earthlike atmosphere forever.
The "easy" solution is to just keep adding required gases into the atmosphere. Which, if you were able to do it the first time, you can probably keep doing. This would still be a matter of millions of years, it's not like your Martian biosphere suddenly runs out of oxygen just because you forgot to add this year's oxygen supply.
Pornelius_McSucc OP t1_j8r86h2 wrote
I honestly think the better move for a permanent terraform would be Venus, and Mars would work well with a "temporary" terraform like you describe. Venus is the only planet with real potential to be a sister Earth. There are multiple processes theoretically possible that would convert its atmosphere to the right composition and lower the temperature, at an exponential rate. These methods in conjunction could completely change Venus in a matter of a few centuries. The biggest thing it seems would be to accelerate its rotation. Which is a lot more difficult for a type 1 civ than all the other tasks such as adding water and converting the atmosphere. The energy and technology required to exert a meaningful positive rotational force on the planet is well, astronomical. And you also have to consider that to turn on the geological magnetism you may need to divert a moon to Venus. But I think Mars could be great practice for these things on a planetary scale.
zolikk t1_j8r90fu wrote
A funny notion concerning Venus, connected to the "necessity of a magnetosphere", is that Venus also happens to have no magnetosphere. Yet it is fully capable of maintaining a thick atmosphere over geological timescales. Despite being hotter and closer to the Sun, its gravity does the job of keeping the atmosphere on the planet. Well, other than H and He, which will be blown away by solar wind (though the Earth loses these over time as well).
Venus doesn't have water, which indeed might be related to its lack of magnetosphere. Water vapor in the upper reaches of the atmosphere can ionize, and the H can be blown off by the solar wind. This might be how Venus lost all its water in the first place, and why it has so much CO2 gas, because without water it won't become bound to rocks like it does on Earth.
So, naturally, the "simple" task of terraforming Venus is probably to "just add water". And yes, you are right, Venus might be a much better early candidate for terraforming due to this. It is closer to the Sun, it has the right gravity etc. Mars is a better candidate for early human (artificial) habitation, but if we can terraform Mars we can probably also terraform Venus and it'd produce better results. And I don't think you really need to accelerate its rotation (unless, again, you're trying to make a magnetosphere perhaps?)
kerfitten1234 t1_j8rewyz wrote
Venus wouldn't be quite that simple. Water vapor is a greenhouse gas. Any attempt to add water to Venus would cause it's temperature to go up, not down. You'd have to cool Venus down first, then add water.
drgath t1_j8rurkx wrote
Out of curiosity, what ways exist to cool down a planet like Venus, if you can’t just add lots of ice?
kerfitten1234 t1_j8rvx4o wrote
Put a ring on it to shade the surface. A polar ring at about the right altitude might also give it a more earthlike day/night cycle.
danielravennest t1_j8tm679 wrote
> the "simple" task of terraforming Venus is
To drag several cubic km of metallic asteroids to Venus orbit, heat up chunks with concentrated sunlight, and roll it into thin sheet metal. Then use it as a sunshade to block out the Sun from the whole planet.
On a time scale of 40 years the atmosphere will cool down. It takes so long because not only is the atmosphere much more massive than Earth's, but the surface rock layer just below the gas is also at the same temperature, and has to lose heat too.
The high ground on Venus will preferentially be cooler and lower pressure, so that's where you can start doing stuff.
3d_blunder t1_j8vhssr wrote
Getting Venus to spin at a comfortable rate is IMO the big sticking point: doing so would probably involve so much energy the planet would be pure lava and take millennia to cool down.
northaviator t1_j9782ch wrote
Venus turns to lava regularly, on a geologic time scale. It's why there aren't many craters on Venus.
3d_blunder t1_j97s6ki wrote
TIL! Still, what mechanism could we use to increase its spin? If it happened to blow a big chunk of the atmosphere away I think that's a plus, no?
I'm still surprised that "total sun-shading" seems to have a consensus cooldown period of less than a decade.
kerfitten1234 t1_j8rei53 wrote
Uv rays don't give a shit about the magnetosphere, they are blocked by oxygen molecules in the atmosphere. That's where the ozone layer comes from.
danielravennest t1_j8tl8u1 wrote
The combination of a magnetic field and atmosphere protect the Earth's surface from high levels of radiation. The atmosphere does most of the work.
An equivalent mass of anything will do the same job, more or less. Build a habitat dome with 4 meters of glass, and you are protected. This can be multiple panes for practical manufacturing and safety. Or an equivalent amount of dirt piled on the dome with sunlight piped in through side windows.
If you pump up the atmospheric pressure to Earth levels, it will be more than enough. Mars' lower gravity means you need more atmosphere thickness to generate the same pressure.
RollinThundaga t1_j8sds4p wrote
You're thinking of Ozone, which will be synthesized via photochemistry and lightning once an atmosphere is in place.
Edit: we also produce it as a lower-atmosphere pollutant, so maybe we'll be good if we run a coal plant on Mars for a few centuries 🤷♂️
Advanced_Double_42 t1_j8tm6c2 wrote
99.86% of the solar systems mass is in the sun. Over 70% of that is hydrogen that could be used for fuel.
I can't imagine a Type II civilization ignoring such a massive resource. Even if they simply end up "mining" the sun for hydrogen that they use for fusion reactors elsewhere. If they are not taking full advantage of their star, I don't think they can even be considered a fully-fledged Type II
zolikk t1_j8tmhth wrote
Yes, I imagine such a civ would just scoop up hydrogen from the Sun and run something like an artificial CNO cycle in reactors with that fuel. It makes more sense than using a dyson swarm.
What I meant there is that you can out-power the Sun's output easily even without that, by using the fuel on outer gas giants too. So technically you do not need to do anything with the Sun in order to "reach Type II" (it's defined by power generation, regardless of source).
northaviator t1_j978d89 wrote
It would be far easier to get your H2 at An Ice giant.
Advanced_Double_42 t1_j9f28ud wrote
Of course, but when all the H2 in all of the gas giants has been mined and fused, there will be ~500x more waiting in the sun.
danielravennest t1_j8tk770 wrote
> artificial methods would take a lot.
Mars is orange because of rust. Turn the rust back to iron, magnetize it, and point all the magnets the same way. No energy required to maintain.
The core of Mars is about 1500 km down from the surface. The mantle density is about 3.5 tons per cubic meter, which at Mars gravity produces a rock pressure of 13 MegaPascals (MPa) per km. Basalt, which is volcanic rock that Mars has lots of, has a maximum compressive strength of 338 MPa. So by the time you get 26 km down, the rock will definitely fail and your drill hole will collapse.
The best steel has about 5 times the strength, but 2.2 times the density. So if you use it to line a drill hole, it will collapse under its own weight at 58 km. You are now 3.9% of the way to the core. The core is out of reach with known technology, so forget doing anything to it.
YpsilonY t1_j8rhdx1 wrote
Without doing the math, I'm pretty sure you could run an artificial magnetic field or just keep topping up the atmospheres for millions of years using less energy than it would take to move Ceres or melt Mars's core.
Pornelius_McSucc OP t1_j8ri2tj wrote
I think it is half the opposite because all you would need for heating the core is a BIG nuke unless you did it electrically. It is however likely that it would take less energy to just top up the atmosphere than to move Ceres to guarantee the core would be functional.
YpsilonY t1_j8rxy16 wrote
So my back of the envelope math says heating Mars' core from 1400°C (estimated temperature, exact value unknown) to the melting point of iron of 1538°C would take 8.21*10^20J or 2.2 billion TWh. So 100.000 times the current worlds yearly energy consumption.
How you produce that energy is kind of irrelevant, but assuming we use a perfectly efficient hydrogen bomb that somehow converts all it's mass into energy using deuterium tritium fusion, we'd need approximately 10.000.000 tons of hydrogen. Half of that deuterium and half tritium. That sure is one Big nuke ;)
Pornelius_McSucc OP t1_j8rybhw wrote
Well that no longer seems practical.
RollinThundaga t1_j8sde9w wrote
"Energy is finite" but Jupiter and Saturn are literally made of mostly Hydrogen. Even ignoring stellasers and solar sails, there's enough fusion fuel to last a long time, and more than enough for a continuous Kuiper belt mining operation.
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