I’ve always wonderd if humans could live on planetary moons which have atmospheres. Take a rather large moon like Ganymede. Would a human colony be able to survive there? Sunlight is too low for growing crops-is there any internal energy sources that would substitute? Plus the cold-if they built caves under the surface, would that be OK? Or is Mars just about the only place where humans (albeit with great effort) could colonize?
The night sky from Ganymede has got to be spectatcular!
My understanding is that Ganymede, Callisto, and Europa: (a) effectively have no atmosphere (like our Moon, they have an ‘atmosphere’ that is a vacuum not quite as totally gasless as the surrounding space), and (b) they are substantially too cold. While Mars’s temperature ranges from just barely cold enough for CO2 to form ‘dry snow’ up to “Earthside brisk fall/spring day” on the hottest of summer days near the equator, the Jovian moons average temperatures 100 degrees or so colder. Colonizing them, and even more so Terraforming them, would be substantially more difficult than the equivalent for Mars.
Io, on the other hand, is uncolonizable for different reasons. An electromagnetic flux tube connects it to Jupiter and keeps the surface roiled. It would be like trying to build a home in the middle of Kilauea to attempt to colonize Io – not to mention that there is the potential for radiation poisoning from particles caught in the radiation belt that causes the complex surface conditions.
Doesn’t Jupiter also lack an equivalent of the Van Allen Belts to help ward off solar and cosmic radiation, or did I read that in a comic book somewhere?
Note to comics fans: No, I do not equate reading something in a comic book with reading something factually inaccurate.
To the contrary, Jupiter has a huge magnetosphere:
I’m probably thinkin’ of Mudd’s Planet, then. Thanks!
First of all, it is the magnetosphere, not the Van Allen Belts, which ward off charged solar radiation (mostly electrons). Van Allen Belts don’t provide protection (or at least, not much) from solar wind. The bulk of extra-solar cosmic rays are protons or charged alpha particles which have too much energy and are moving too fast to be significantly affected by the magnetosphere; when they impact molecules in the Earth’s upper atmosphere cosmic ray spallation results, which creates large numbers of energetic charged particles. (It is actually these, not the cosmic rays themselves, which present a background radiation hazard.) These actually feed and sustain the natural Van Allen Belts. The Starfish Prime high altitude nuclear test shot actually created an artificial radiation belt that put several satellites out of commission.
Second, as Cerowyn already noted, Jupiter has a massive and very active magnetosphere, and some huge radiation belts (and the afformentioned flux tube between Io and Jupiter), which does make transits in the inner Jovian system hazardous for robotic probes and lethal to unshielded humans. It’s a real problem when plotting swing-by maneuvers for probes to minimize duration in the high radiation areas.
Third, you may be thinking of Saturn, which does have a very modest magnetosphere and surprisingly low radiation hazard. Although further from the Sun, Saturn might be a more ideal spot to set up your orbiting resort hotel (though the rings aren’t nearly as impressive up close).
Fourth, the amount of Sunlight you’ll get at the orbit of Jupiter or further is insignificant, so you’ll definitely have to come up with some scheme for creating artificial UV light to grow crops, et cetera.
Personally, I have my doubts that even Mars would be suitable for colonizing. Once you’ve created the ability to support a sustainable population in space long enough to transit from Earth to Mars (assuming a low energy Hohmann transfer orbit) you’re probably pretty close to just being able to build and live indefinitely in orbital habitats. Once you can do this, planets–particularly ones lacking a substantial atmosphere or outside the Sun’s habitable zone–just aren’t that appealing, at least not for mass colonization. Science fiction stories about terraforming Venus or Mars, or “warping” to other systems to colonize “M-class” planets are fun, but by the time such a capability realistically exists I doubt we’ll have much use for planets. Living on a planet is the default because it is the environment which naturally supports us, but they’re a massive waste of resources and add great expense in terms of energy and work to get away from.
Stranger
I tend to agree with this. On Mars you have winds, dust, extreme cold, and other problems.
If the moon has significant amounts of water, it makes for a much more appealing home away from home. In particular, there may be uncollapsed lava tubes which could provide huge caverns suitable for colonization. Protected from cosmic rays, huge colonies could be built in these tubes if we can find some uncollapsed ones (or even one). You’re only a day and a half from Earth should something go wrong.
Asteroids might also make nice abodes if we can figure out a way to bore or melt our way into them. Or since many of them appear to be very loosely packed and possibly easy to mine, we might be able to make a form of concrete from the material and build large habitats on the surface.
Unless the nuclear waste dump detonates.
Well, the only reason I can see for a long-term, non-scientific reason for a Mars colony would be something happening on Earth that would make it less habitable. A serious shift in natural resources, some kind of disaster/nuclear winter, etc…If that were the case, then you would want to go to a place that, ideally, can be terraformed to replace all the resources you lost, or might lose in the foreseeable future.
Plus, people like gravity, and would tend to miss it if they lived in an orbital station (cause contrary to what a lot of science fiction writers think, I have serious doubts about artificial gravity ever being invented, aside from spinning sections inducing a centrifugal force.)
But Earth even after an ecological disaster on the order of the Cretaceous-Tertiary impact would be much easier to terraform back into a human-habitable world than Mars.
Of course artificial gravity isn’t going to happen, despite not really violating the laws of physics like other science fiction commonplaces like FTL/time travel. But what’s wrong with spinning habitats? Spin is perfectly acceptable if you need “gravity”.
If your entire ecology on Mars is under domes or in caves, and heat and light are provided by nuclear reactors, and the colonies are self-sufficient, why do you need to build the dome on Mars?
Here on Earth we are up in arms about a miniscule shift in the composition of our atmosphere. I’m not familiar with any plans for a “terraforming” process that could easily remove just a percent or so of carbon dioxide from our atmosphere. The think that we could just up and add an atmosphere to a planet that basically has none is quite a leap.
Also, Mars has no magnetic field. It’s atmosphere was scoured away by the solar wind since it has no protection from a magnetosphere. After we figure out how to produce an atmosphere there, we’d need to constantly replentish it.
I think terraforming Mars is going to be a bit more involved than we can handle.