Which Planets & Moon are Habitable in the Solar System?

Let’s say we suddenly developed super-fast propulsion systems that could transport massive quantities of oxygen and food to the far reaches of the solar system.

Which of the solar system’s planets and moons could we settle–today and, say, 100 years from now?

Is the dark side of Mercury cool enough–or would the solar radiation and cosmic rays prove too damaging?
Yes, Venus has crushing atmospheric pressure, but could it be counteracted somehow?
Same with Jupiter’s moons: Would the radiation be too harmful?

My guess is:
Mercury: no
Venus: no
Mars and moons: yes
Asteroid belt: yes
Jupiter: never moons: not for long periods
Saturn: no Moons: not for long periods
Uranus and Neptune: no Moons: yes.
Pluto: yes

Next, guesstimate if any technology that might be developed in, say, the next 100 years would make a difference. (Too difficult to guess technological development? Tough. Do it anyway!)

Unless you actually did see it, you might have just missed the Discovery Channel (?) special ‘95 Moons and Counting’, narrated by John Lithgow. It covered the habitability of many of the moons around the solar system.

Uranus’ and Jupiter’s moons seem the most promising, due to possible water content. Phobos is also considered, due to its proximity. They posited new versions of extreme sports – swimming like a dolphin in low-gravity oceans, ballooning in a methane atmosphere, rock-climbing on enormous cliffs on which you weigh only a few ounces, etc.

I think some of these would be habitable now, as long as the transport systems you mention could be put in place. After all, we’ve had space stations operating for a number of years.

First off, Mercury doesn’t have a “dark side.” It was once thought to, but radar experiments in 1965 showed this not to be so. Mercury rotates three times for every two revolutions around the sun. So it’s right out – surface temperature varies between 90 and 700 Kelvin.

The problem with Venus is not only the pressure (90 atmospheres, for those keeping score at home), but the temperatures of 400 to 740 K and the clouds of concentrated sulfuric acid. Extremely inhospitable, to say the least.

MArs, maybe, with some serious expenditure for habitats. And lots of water, which is heavy and expensive to transport. But Phobos and Deimos are both pretty small, and have eccentric, unstable orbits.

Jupiter’s moons are a mixed bag – some are too hot, some are too cold. Some have lots and lots of active volcanos. And I mean active, like 300 km plumes of lava on Io. Bad idea.

Pluto is way too small and way too cold. The warmest it gets is about -200 C. Oh, and it’s atmosphere freezes from time to time. Like, most of the time.

In 100 years? Who knows? Some of our resident futurists can speculate on that.

There is evidence of considerable liquid water on the ancient Martian surface, and some evidence of liquid water flows in the relatively recent past. The polar ice caps should also contain significant reservoirs of water.

According to what I’ve read, Mars is the only likely candidate, unless you count domes or underground habitats. It’s no good right now (cold, almost no air, and nothing breathable anyway), but the idea of terraforming it by dropping comets on the (somewhat hypothetical) icecaps is pretty straightforward, even with current technology. It would take a major engineering effort to get going, but no big scientific breakthroughs. Once Mars had some atmosphere, it would warm up enough for liquid water, and we could start seeding it with bacteria and eventually plants to produce oxygen. (Yes, it’s a long-term project.) IIRC, the proponents of the idea say that the atmosphere would leak away after only a million years or so, but that’s not really an emergency.

Anything else around is likely to be too hot or too cold, or too small to hold an atmosphere, or even, as the gas giants are supposed to be, lacking any kind of solid surface.

Maybe permanent space stations with a self-sustaining ecology would be easiest.

don’t forget Charon, Pluto’s little friend. which gets a yes we probally could (though we know almost nothing about it)
----but why would you want to…

Mercury maybe with a solar shield,
forget venus, jup, sat, nep, urn

moon,mars +2 ‘moons’, astroids, many other ‘moons’ probally


Yes, let’s allow domes for inhospitable temperature extremes. And maybe even caves for radiation–if that would work.

My question about some of these moons is that even if water is plentiful, how can you possibly drill 100-200 miles underneath the surface of a distant moon? Do you fabricate the drill shafts and bits on site? How? I think the deepest wells on Earth are maybe 4 miles deep.

The Jupiter system is no good. Jupiter is an intense source of radiation at levels that are lethal to humans.

Since (in the US) you can’t even build a shed on land labeled “wetlands” (=swamp) here on Earth, I don’t see how terraforming Mars would be acceptable when the time comes :rolleyes:


So long as you do it peacefully, it is not prohibited. From the Outer Space Treaty of 1967:

The only other restriction seems to be that, when on other celestial bodies, you must play well with other children, and don’t bring home any space germs:

I suppose the phrase “harmful contamination” might provide a window for Space Environmentalists, but in the absence of any defining law, I would think that pretty much anything goes.

Yes, I guess I did ignore environmental preservation in my post, and wouldn’t advocate terraforming anything until we’re sure there isn’t any native life or other interesting features.

tsunamisurfer, with some sort of enclosure and enough power, we could plant a colony just about anywhere that we could tolerate the gravity. But where’s the fun in that? I want to go outside!

Except Venus–crushing atmospheric pressure, lead-melting temperatures, corrosive air blasted by 300-mph winds. Not exactly the Bahamas.

I suppose a follow-up question would be: can anyone envision man EVER standing on the surface of Venus? Or is it a complete write off?

(Realistically, what society would fund a space program to another star system, say, 30 light years away, that even at near relativistic speeds, would mean a 100-year payback for the taxpayers who fund the program? Will humanity ever been THAT forward thinking? (Why do I feel someone is going to say “wormholes”?)

Hmmm. if you have super fast propulsion then things are interesting. You could divert comets into hitting Mars, depositing water, which is incidentally a greenhouse gas. You could drop very dark comet nuclei (like Kuiper Belt objects, those super-comets out past Pluto) onto the polar regions, releasing more water and CO2. You could probably warm Mars up a lot that way. And it’ll hold that atmosphere
for a long time. You could even do this to the Moon; pick up comets high in oxygen and nitrogen and bombard it until it has an atmosphere. It would hold a good atmosphere for a long time too. You’d need to drop another comet onto it every century or two, but you could lower it down slowly and let it relaease more air.

Hey, this is fun! What else can we do?

Hmm. My understanding was that terraforming Mars is a nice fantasy, but it’ll never actually work, even given lots and lots of time. This is supposedly because its internal magnetic dynmo thingy has stopped, killing its magnetic field. And without a magnetic field, Mars isn’t shielded from the solar wind, which strips away the atmosphere. So we’d need to restart the dynamo first, which seems, um, somewhat out of our reach, technologically.

I do think we’ll have had a handful of people on Mars in 100 years’ time, but large-scale settlement is probably a long way off. It’s my opinion that we’re not going anywhere until we sort things out down here on Earth.

John Varley has several stories set in a future history where Venus (and much of the solar system) has been colonized. The people running around on Venus have some pretty advanced technology helping them, though (magnetic force-fields keeping the hotile elements out).

Nah, not really. Io would be out, for that reason, and also because it’s the most geologically active body in the solar system! But the rest of the Galilean satellites would probably be fine, and the outer irregular satellites would be safe as houses, radiation-wise.

Whoops, missed this the first time through.

Actually, there’s next to no wind at the surface of Venus, just a few km/h at most. The whole surface is pretty close to the same temperature. The 300-mph winds are at the cloud-tops.

You gonna make something of it? :frowning:
FWIW, my orbit is good for another 50 million years…long enough to support a colony for a short lived species like you humans.

Wetland regs are for the protection of an important ecological habitat, not to mention the benefits of flood control, water purification, etc.

If Mars is indeed a dead planet, then terraforming would be the beneficial creation of a viable habitat. The Mars Environmental Protection Agency and the Army Corps of Martian Engineers should not mind. But perhaps the pro-lithic special interest groups will have something to say about it.

(If Mars has some bacterial life or whatever, then we’ll have some ethical questions to consider about colonization there as I discussed in a past Great Debate.)

oops, I meant :mad: !


Phobos and Deimos certainly are unsuitable for colonization, but not because their orbits are “eccentric.” In fact, these two moons have almost the most perfectly circular orbits of any bodies in the solar system. It’s one of the mysteries of the Martian system, because except for the orbits they seem to be captured asteroids.

To the OP and others interested in this topic, I recommend the book Terraforming by Martyn Fogg. It reads like a textbook; in fact it IS a textbook, but it keeps fantastic speculation to a minimum and all of its ideas are based on current or easily-extrapolated technology. He covers the possibilities for every planet and moon, as well as O’Neil colonies and such “paraterraforming” concepts as doming over craters or roofing over Martian canyons.

Luna (our moon) could be terraformed more easily than most people think. Wouldn’t it be neat to someday look into the sky and see another blue-green world winking back at us?