As I understand it the Earth’s magnetic field helps to divert the solar wind that would otherwise strip away our atmosphere. I also understand that Mars and Venus have fairly weak magnetic fields. Mars’s atmosphere is very thin (compared to our own) and Venus’s is slowly being blown away. A lot of us think, in our idle moments, of terraforming other planets.
Mars: Has a thin atmosphere. Assuming there’s some way of thickening it (and I don’t know of any except perhaps turning on the giant Martian nuclear-powered machine in a film whose name escapes me), what’s the use if it will only be blown away? If an atmosphere were somehow made, how long would it last under the solar assault?
Venus’s atmosphere is also under assault, but it’s much thicker than ours. At the current rate of loss, how long would it take to get down to two or three Earth-atmospheres pressure? If it does, then how could it be altered to support terrestrial life?
Atmosphere loss to solar wind is pretty slow, right? To human reckoning rather than geologically, I mean. If we have massive devices in place to thicken Mars’ atmosphere, surely we could easily keep up. Of course, every so often we would need to bring in a comet or something for resources, but that shouldn’t be too much trouble given the scope of the project.
One of the stock proposals for terraforming Mars is to redirect comets to hit the poles. That way both the comet and the icecaps would vaporize. Both are full of greenhouse gases that would warm things up and melt the icecaps even faster.
I’ve seen one estimate that an earth-like atmosphere on Mars would last about a million years before getting too thin to breathe. That’s not long in planetary terms, but in human terms it’s not really an emergency.
For a while, new technology was big on talk and big on delivery. Let man fly. No problem. Make super-powerful computing devices. Piece of cake. Put man on the moon. You tell me when.
These current plans like teraforming are so far out there that the talk should be left to science fiction novels. Even the beginning logistics let alone the science behind it are so far out of reach that we shouldn’t waste any energy thinking about it further.
Call me when we have a full-sized underwater city, the Sahara desert is fertile, and Antarctica is the world’s biggest exporter of tomatoes.
Given that we have very little grasp on how our own climate and atmosphere function over the long term, anything that could be said with regard to the terraforming of other worlds is highly speculative. We can assume that any tenative proposals–Sagan’s notion of reducing Venus’ atmosphere by seeding it with alge, or Zubrin’s plan to cover the Martian poles with carbon black or black alge to absorb heat and melt the ice caps, increasing atmospheric water–fail to recognize many of the regulatory mechanisms which will require adjustment and compenstation to force a conversion. Also, the issue of a significant magnetosphere (or the lack thereof with regard to both Venus and Mars) is a serious concern; even with a thickened atmosphere, ionizing solar radiation would pose a problem for long-term occupants, and their communication and electronic gear. And then you have to cope with boosting people up and gliding them down to the surface (assuming one of the purposes of colonization is resource exploitation and interplanetary trade).
My personal opinion on the matter is that by the time we have the technology and logistical capability to terraform worlds we won’t want or need to live on the surface of a planet. Worlds are (relatively) stable and secure, but they’re also massively inefficient uses of space and material. No doubt people will continue to live upon or visit the surface of planets, but extraTerran colonization, if it transpires, will most likely involve solar-orbiting habitats rather than modifying worlds to suit our needs.
But either way, that’s a long way off; at the current rate of progress, centuries. Meanwhile, we need to figure out how to preserve and protect the planet we have here; the one that we are specially evolved to inhabit.
Free science fictiony idea - when we have wormhole technology, open up a series of portals along Venus’s equator with the other end surrounding Mars’s equator. How long would it take for one million portals, each ten meters in diameter, to bring Mars up to near-Earth pressure? And if the process is repeated, how long before Venus runs sufficiently low that it can be colonized?
Venus Facts.
Much, much, much thicker than ours…95 Earth Atmospheres. I think getting rid of (condensing and boxing it up or bleeding it off into space) 93 of those atmoshpheres (primarily CO2) will be harder than controlling CO2 levels in our own atmosphere (obviously). That project would would take an incredible amount of time to make it hospitible. Do we even know of any type of bacteria that could even survive 900F temps?
And these two facts:
Venus circles the Sun every 224.7 Earth days.
One Venus day would equal 243 Earth days.
Means that there is virtually no magnetic field because the planet rotates very slowly (almost locking one side towards the Sun)…resulting in long term solar exposure followed by long term night. Those two components will not be fixable, and may doom the endeavour from the start.
Mars Facts.
Mars on the other hand, has less atmoshpere, but it would seem easier to add to the atmosphere to get it from 1% EA to 75%-90% EA considering that Mars has a smaller “volume” to fill, plus inhabiting a deeper valley would make it easier to attain acceptable atmospheric pressure.
Fact: Mars has a rocky interior that’s low in metal (iron sulfide).
No magnetic field is still problematic though.
Doesn’t Mars have the fundamental problem that it’s simply not massive enough to keep a decent breathable atmosphere? Plus, it’s outside the sun’s life zone.
As for Venus, wouldn’t we have to move it to a cooler orbit? And let’s give it a moon while we’re at it. Could we do that without affecting the Earth’s orbit?
If we ever got to the level of technology where we could move planets to new orbits or transport significant portions of the atmosphere of one planet to another, we probably wouldn’t need to do any of those things anymore, because by that time, we should also have the technology to build Ringworlds and Dyson spheres, or for that matter, modify ourselves so that we can survive comfortably in hard vacuum and feed directly on solar radiation.
That’s certainly speculative, but it seems likely that for any long-term space habitation or interstellar travel, humanity (or the inheritors begat by humanity) will have to be modified to withstand the environment of space (vacuum, radiation, et cetera) as well as eliminating the comsumptive and excretory faculties which, however well they may serve us on Earth, require a disproportionate amount of space and mass for space travel. And nobody wants to sign on the crew manifest as “Personnel, Lifesystems Engineering, Plumber, 3rd Class”.
Venus would be much tougher to terraform than Mars, because Venus is very, very hot. And there’s no real way to cool it down, other than blocking out the sun and letting it radiate heat away into space - a process that would take a very, very long time.