Habitable planet discovered...
- Thread starter Joel_Kirk
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ProtoAvatar
Fleet Captain
Mars and Venus both don't have magnetic fields.
Mars's atmosphere was stripped from the planet, Venus's, not - not even close.
The magnetic field alone does not determine how much atmosphere the planet will have.
As for Mars - even if, after being terraformed, he will loose atmosphere, an atmosphere replenishment every hundred thousand years (barely an effort for people who can terraform a planet) would solve the problem.
The problems with terraforming Mars are the cost and the time of this undertaking.
It would be much cheaper and faster to build O'Neill colonies - and they would have other advantages: no delta V (as opposed to a planet), increased confort, potential economic prosperity (from surface mining asteroids, as opposed to burrowing the ground on a planet for resources).
It doesn't seem to be a problem that if it takes 'a hundred thousand years' (your arbitrary measurement) to strip a planet's atmos then it's highly likely that it will take that amount of time to build it up in the first place.
As to magnetic fields - Mars is too light to hold on to any atmosphere without a magnetic field, Venus isn't but any useful atmosphere has been stripped.
As to magnetic fields - Mars is too light to hold on to any atmosphere without a magnetic field, Venus isn't but any useful atmosphere has been stripped.
I'm guessing that when you say no delta V, you mean there's no significant gravity field for a ship to escape?
I'm not sure that O'Neill colonies are as attractive an option as you think they are. They don't really create any of their own resources, you're having to ship all the required materials from Earth to construct them (though asteroid and comet mining mitigates this somewhat). They're totally unshielded by their environment from natural disasters, though surface colonies might have to contend with severe weather conditions.
There might be some things I'm missing out in terms of their advantages though, besides their mobility and near lack of delta V required for leaving them.
ProtoAvatar
Fleet Captain
Hardly.
The solar wind is not particularly efficient at stripping an atmosphere from a planet. My hundred thousand year estimate was on the pessimistic side, Deckerd.
And, even today, we have physically feasible ways of terraforming Mars that can build up Mars's atmosphere in considerably less time than 100000 years - a few thousand years, at most.
You are arguing that Venus has a dense atmosphere and Mars almost no atmosphere because Venus has more mass than Mars aka MASS is the determining factor, NOT magnetic fields (a departure from your previous position).
ProtoAvatar
Fleet Captain
You can picture delta V as the energy expended to escape a gravitational well.
You could never mine Mars, export these resources and make a profit (due to this energy expenditure).
You could easily make a profit from mining asteroids, you being stationed in a relatively nearby O'Neill colony.
You don't lift resources from Earth's gravitational well (expending energy) to construct O'Neill colonies.
You have all the resources you need to construct such colonies and to assure their economic self-sufficiency in asteroids, etc (far more than are to be found on Earth or on any other planet).
As for 'natural disasters' - a space structure the size of O'Neill colonies can easily be shielded from radiation better than we are here on Earth; asterois and other objects are highly improbable to hit O'Neill colonies (hitting Earth is far more probable) because of the relatively small size of these colonies, because you are free to choose where to build them, because active anti-asteroid/object measures are FAR easier to implement than they are from Earth, etc.
In conclusion, building O'Neill colonies has many advantages over terraforming planets and almost no disadvantage.
ProtoAvatar
Fleet Captain
Deckerd - Venus has a lower mass than Earth's, has no magnetic field and has an atmosphere densed than Earth's.
Earth's mass is more than large enough to 'hang on' to its atmosphere with or without its magnetic field.
As for Mars - most likely, the primary reason it lost its atmosphere was its lower mass; or, perhaps, a cataclismic collision was the cause.
The lack of a magnetic field may have accelerated the process; it was not the primary reason for Mars losing its atmosphere.
ProtoAvatar
Fleet Captain
These instruments only have to be lifted ONCE, and their weight is small enough that you can easily launch them from Earth.
You have to lift at least as many (and as heavy) Earth-made instruments if you want to terraform a planet.
If you don't beleive me, go to wikipedia (or other sources) and check the physical characteristics of Venus, Earth and Mars.
You'll find my description accurate.
ProtoAvatar
Fleet Captain
What i said about the need for Earth-made instruments in order to terraform a planet is easily applicable to living in a dome (you have to build) on a planet or simply building a colony on a habitable planet.
In my opinion, the future of space colonization lies with O'Neill style colonies.
Terraforming is a byzantine enterprise that provides no advantages over said O'Neill colonies.
As for habitable planets:
First of all, you'll have to get there - and interstellar travel is a LOT harder than what's shown in star trek;
You'll never find a planet with the exact conditions from Earth; you will probably find life, and here ethical and ecological considerations come into play.
Between the tidal locking, close distance to its sun, and at least 3 earth masses, it is mostly speculation as to tha habiltable part.
Thanks for the link, SPCTRE-- good one.
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