Some thoughts on solar-system engineering:
One idea out there is to change the orbit of a good-sized asteroid or comet — about 100 kilometers in diameter — so that it swings by one of the inner planets and then back out to, say, Jupiter. As the cosmic tow truck passes our target planet, it uses its gravitational attraction to tug the planet in the desired direction, then hurtles back to slingshot around Jupiter, picking up more energy in the process. Repeat a few thousand times with a few score asteroids and there you go: Mars in your backyard.
This technique has been proposed as a way to drag Earth away from the ever-brightening sun that otherwise will eventually snuff out life on our planet. It has some downsides, though. One is that each time the asteroid comes by it’ll exert a tidal force ten times greater than the moon’s, wreaking havoc on the oceans and weather. Another is that some Poindexter on the relocation team is bound to make a unit conversion error along the way, and when the asteroid slams into the Earth — well, that’ll be a real pisser. Luckily, we don’t need to worry about things like that if we’re moving Mars or Venus: if we make one planet go boom, we’ve still got a spare.
Once we get the planet where we want it, though, we’ve still got our hands full. However bad the environment on Earth is, Venus’s is worse. Atmospheric pressure is roughly 92 times ours, the planet has no free oxygen or water to speak of, and the surface temp is hot enough to melt lead. Mars has an extremely thin atmosphere but its temperature, while chilly, isn’t so bad, and it’ll get warmer when it’s closer to the sun. That alone might cause enough melting at the Martian poles to release ice-bound CO2 and create a greenhouse effect. If not, we can always try focusing the sun’s rays with orbital mirrors or crashing (smaller) asteroids into the ice.
I don’t see a calculation of what would happen to Venus’ surface temp if it were farther out. Most terraforming plans of either planet don’t generally include moving them to a better location, but it’s worth thinking about — it is, after all, the first three rules of real estate.
Why don’t we disturb the orbits of some of those asteroids in the belt between Mars and Jupiter to send them crashing into Mars? We could build Mars’ mass up to near that of Earth so it could hold an atmosphere. We could even give Mars a real moon. I’m sure as we built its mass and therefore its gravitational attraction, it would help our cause by sucking in some of the nearer asteroids without our help.
It seems to me that what’s heating Venus is internal fission reactions rather than the Sun. Maybe all Venus needs is a Moon to stabilize its spin and some time to cool down.
Why don’t we disturb the orbits of some of those asteroids in the belt between Mars and Jupiter to send them crashing into Mars? We could build Mars’ mass up to near that of Earth so it could hold an atmosphere
The mass of mars is 10.7% of the mass of earth.
The mass of the entire asteroid belt is about 0.5% of the mass of Mars.
So, no.
Dfens:
That’s actually the vital question: what portions of Venus’ temperature are due to (1) the additional solar energy at it’s orbital distance, (2) internal heating ala Earth’s, and (3) ‘greenhouse effect’.
Moving the planet only cures (1).
I don’t have a link or citation, but Jeff (Geoff?) Landis at NASA (and Analog) has been half-jokingly suggesting colonizing the upper cloud deck of Venus for several years. If I remember, it turns out that at the altitude that the pressure is about 1 Earth atmosphere, the temperature range is approximately Earthlike as well. I don’t know about the H2S04 content, though.
The mass of the entire asteroid belt is about 0.5% of the mass of Mars.
So, no.
Paul, why do you always have to be such a party pooper, what with your numbers and facts and stuff? 😉
Has anyone calculated the chemical effect on the atmosphere that would result from reducing (1)? Some things would tend to precipitate out, I would think, and behave differently as liquids than as gases. Having more interaction with the soil would also cause chemical changes, for good or bad.
Some info if you want to read further: this was Greg Laughlin’s idea (and by the way, today he has some Alpha Centuari related news on his website: http://www.oklo.org) Laughlin has written extensively about the stability of the solar system — whether Mercury can be expected to stick around for the long term, for example. There are some counter-intuitive results when you do modeling. Naturally, moving the Earth or Venus will have an impact on the stability of the rest of the solar system (!) You can find more info on all of this doing a google search on the archives at oklo.org and also by searching google’s archives for “Laughlin” and “moving the earth” and such. (For those visiting oklo.org, note that changing our solar system is very much related to finding and understanding other solar systems.) Another fun tidbit: Charles Stross mentioned that one of his upcoming stories will involve a way to move the Earth which is related to Laughlin’s proposal.
Here’s the paper: http://arxiv.org/abs/astro-ph/0102126
That’s actually the vital question: what portions of Venus’ temperature are due to (1) the additional solar energy at it’s orbital distance, (2) internal heating ala Earth’s, and (3) ‘greenhouse effect’.
Internal heating is negligible for the terrestrial planets. IIRC, heat flow out of the earth is on the order of a terawatts; insolation reaching the surface is around 100,000 TW.
The increase in temperature from increased insolation would go as (insolation)^1/4 power, assuming no change in albedo or IR emissivity. In actuality, Venus has a higher albedo than Earth, so (if I’m calculating this right) the amount of solar energy absorbed there per unit area is close to that of Earth.
We can conclude the high surface temperature of Venus is due to the very thick atmosphere, retarding escape of what solar energy is deposited there. A very high temperature difference ends up being needed to reach equilibrium.
The problem with any planet other than Earth is gravity. Our biology has evolved under a constant 1 g for billenia, so I’d be pretty surprised to discover no odd dependencies on that. It’s not like sunlight or food access where we have been exposed to a range of stress; it’s always 1 g down here.
We already know 0 g is fatal given time, but we don’t even know for sure if Venus’ 0.91 g is good enough. I hope it is, but I suspect that (barring technological manipulation of local gravity) only O’Neil cylinders will be appropriate for long-term off world settlements.
I do like the idea of colonizing Venus’ upper cloud layer though. It has much to recommend it. We could crash a couple of the larger iceteroids into it first to lend its atmosphere harvestable moisture.
I do like the idea of colonizing Venus’ upper cloud layer though. It has much to recommend it. We could crash a couple of the larger iceteroids into it first to lend its atmosphere harvestable moisture.
One of the more attractive potential exports from Venus is deuterium (the D:H ratio in its atmosphere is two orders of magnitude higher than on Earth), so diluting that deuterium with a large amount of imported water may not be wise.
Maybe we could use this method to pull the Moon back in towards us and maintain our 24 hour days.
Doing some back of the envelope calculations while trying to sleep a few months ago I figured that the amount of energy that might be derived from dropping a couple of cubic mile asteroid into the sun would liberate enough energy to power a 30,000 ton space craft up to the speed of light. That’s without considering relativistic effects; something always best to ignore when falling asleep.
This is based on the same non relativistic calculation that a pound of anything moving at light speed has about the same amount of kinetic energy as is held potentially by 5 megatons of TNT. Now all I have to do is figure out how to capture that energy and get the patent filed. I will work on that part while others figure how to get the asteroid to crash into the sun in the first place.
I once had an idea that’s right up the alley of this thread. Smash Mars into Venus using the orbital alteration method described, to create a planet with a more similar Earth like mass, the goal being a more Earth like gravity as a result. The creation of a second Earth, if you will. The actual gravity of the second Earth I would not not be able to figure. Venus’ gravity seems high enough as it is that the value of this effort would be marginal, but, as the saying goes, there’s no place like home.
Adding Mercury to the mix would give you a planet with 98% of the mass of the Earth, although how that translates into a specific amount of gravity I would not know. Did a small amount of googling, and here’s a someone’s minor proposal to smash Mercury into Venus, to create a moon, a magnetic field, and a better spin, and those ideas can transfer to the second Earth concept. Not that I’m seriously proposing this; I also favour manufactured colonies with 1g artificial spin gravity rather than terraforming or extreme terraforming, but that’s still a decision left to the future, hopefully.
http://www.halfbakery.com/idea/Crash_20Mercury_20into_20Venus
Why does this have to be done in one go? Mars would be livable, most likely, if it had around the mass of Earth – and Venus is useless for the foreseeable future; the lack of H2O in its atmosphere is just the start of it.
Make exponential growth work for us – send a few dozen von Neumann machines (probably nanotech-based, by the FOTM) to Venus and let them rip, with a command that say 50% of each generation travels to Mars and disassembles itself wherever it lands.
Granted, the resulting planet would be a tad unstable.
Perhaps I should have said “nearer” instead of “near” but none the less, a more massive Mars would be better for our purposes than what we currently have. Since most of the mass of the asteroid belt is concentrated in just a few larger bodies, maybe we could use smaller asteroids like billiard balls to change the orbits of the larger asteroids and send them into a collision course with Mars. I mean, why the hell not?
As for Venus, the sulphur dioxide clouds reflect most of the sun’s energy. That’s why it’s such a bright star. Moving it further from the Sun is not going to change its temperature much if at all. Also since it is so close to us, putting it into an orbit closer to ours carries a small threat to our planet. That doesn’t sound too smart to me. It would be better to do initial experiments of that sort on a planet with a little more room to work with.
No, no, no. Smash Mercury into _Mars_. Throw Ganymede in there too for good measure. These two planetoids (especially Mercury which is particularly dense) both have magnetospheres. Try to round out Mars orbit a bit too while in the smashing process. Then wait a billion years and then hope that Mars now has a nice magnetosphere to protect the whole planet and hold the atmosphere in. Little Ceres will make a nice moon, that seemed important to life here on Earth, so let’s bring it into orbit. Finally toss in some comets for water and terraform the atmosphere as necessary. Enjoy your new planet, now warmed by a brighter sun after all this time! Piece of cake, eh?
Venus is fine. We can live in oxygen balloons in its upper atmosphere, with locally generated magnetic fields. We’ll have to bring our own oxygen, but pressure and temperature at that height is actually quite nice.