atmosphere is predominately CO2. Plants need CO2, so the possibility of growing our own food is very real.

Plants also need oxygen, nutrients and a hell of a lot of other stuff.
Also the atmosphere on Mars is pretty thin and the lack of magnetic field basically means you spend your time getting a lot of radiation fired at you with no protection.

The moon is dead, dry and desolate. Its atmosphere is so thin as to be nonexistent. There is little reason to go back, other than to say we went back. Mars has more potential. It has a thin, but appreciable atmosphere, and that atmosphere is predominately CO2. Plants need CO2, so the possibility of growing our own food is very real. It also has water; whether frozen or liquid is immaterial. Both of these factors means that we can seriously reduce the amount of supplies. Building anything on the moon is kind of like building a house in the desert because it is closer than the fertile valley. Sometimes it is worth it to take the longer trip.

Moon has low exit velocities, and a lot of helium to be mined and solar to be captured. We could well have a robot colony there if not a human one.

I also recall them saying they found water in some of the craters which are always in shadow.

The Moon is a useful jumping off point; a ground + orbital setup would give you a stable body to work from with low gravity. which makes it a logical place to build a ship yard type setup.
There is some protection from the Sun's constant radiation barrage too.

Heck, if you expand upon NASA's Asteroid Capture plan then it would be a good place to park rocks so we can mine them with a much lower risk to all involved.

Really we need a couple of things in place;
1) earth orbit jumping off point - effectively a way station for Earth <-> Space transit.
2) Moon based facilities for a longer range jumping off and industry
3) A shuttle service between 1 and 2.

I would say that all 3 are do able with our current levels of tech, and if not right now getting to the point it would be isn't a stretch, it'll just cost and countries seem unwilling or unable to either stump up the cash alone or work together to get it done - so, like much Sci-Fi, we'll probably be looking at the corporations to do it, which likely means the first solutions will be for resource collection rather than science.

"Plants also need oxygen"

You might be wrong there. Plants need CO2. The only "plants" which need oxygen are fungi and that's because they're fungi not actually plants.

The moon is dead, dry and desolate. Its atmosphere is so thin as to be nonexistent. There is little reason to go back, other than to say we went back. Mars has more potential. It has a thin, but appreciable atmosphere, and that atmosphere is predominately CO2. Plants need CO2, so the possibility of growing our own food is very real. It also has water; whether frozen or liquid is immaterial. Both of these factors means that we can seriously reduce the amount of supplies. Building anything on the moon is kind of like building a house in the desert because it is closer than the fertile valley. Sometimes it is worth it to take the longer trip.

Helium3, 'nuff said.

What did they find on Mars again, Water? Which earth has itself in abundance (or would have at least, if mankind wouldn't reproduce like a bunch of bunnies on blue pills)?

Both are barren rocks that cannot sustain life in their current form. Both have no atmosphere that would be close to thick enough to shield from radiation.

The moon is known to have large Helium3 reserves, which might be a huge boon when tackling the energy hunger of humankind in the nearer future. It is close enough to be a good target for low-cost space travel in the nearer future, and might actually be reachable with alternative, even lower cost ways of transportation like railguns (or "rail-ramps" in this case) in the mid future.

The Mars is still a big unknown when it comes to minable resources, sure water would be great... if the cost of getting water to earth is so high though, this will likely not help us in the future conflicts about water.

And Mars will remain an expensive target until somebody can construct some kind of engine which gets there in shorter time without burning lots of fuel, and can accelerate faster without killing its crew

Its not not science fiction like getting to alpha centauri, which would need a generation ship or some device to get around the lightspeed limit. But its still not even near break even for the near and mid future, not to mention profitable. Whereas the moon might be in the near future.

Which brings us to the real reason why there is no colony on the moon: cost vs. gain. If you need a zero gravity environment to work in for science and other stuff, an orbital station like the ISS is much better than a moon colony. Closer, thus saving on expensive fuel, semi-protected by earths magnetic field, kinda-mobile (if you invest the large sum to tow it even meters from its position, or burn all the fuel onboard )...

When you want to mine the Helium3, you need a) a technology that can use Helium3 (don't know if that exists yet), b) a way to mine the Helium3 and get it to earth cheaper than what you can ask for the Helium3, and c) make sure there is no competing resource that can match the efficiency/environmental footprint/energy density of Helium3 for a lower price.

Add to that the fact that the only reason why Mankind flew to the moon was the cold war between the US and the Soviets which made both superpowers invest ridicolous amounts in technologies and projects that would not yield any economical results for a long time, or ever.... and that the only reason why both the US and the Soviets even had the technology to do so was WW2 and the megalomania of german engineers (which ironically cost germany the war, but was incredibly useful for all the powers that snatched up german brain power and war criminals without a second tought as long as they seemed useful ).

Without the V-Weapons and Werner von Braun no American Astronaut on the Moon.

So basically, humankind threw money out of the window to finance megalomaniacal projects thought out by or derived from war criminals and the weapon industry during WW2 to fast forward decades in their space programs...

It was never something that could have lasted. What we saw in the 80's was the big "space bubble" burst, with people realizing that the space programs where just no economical at all.

What we are seeing now is that finally technology might be at a stage where space travel to near targets (like the moon) might become economical and safe (or safe enough) for the private sector and companies. That is a prerequisite for any colony. If you cannot support it for decades, why go through the trouble and set it up in the first place?

"Plants also need oxygen"

You might be wrong there. Plants need CO2. The only "plants" which need oxygen are fungi and that's because they're fungi not actually plants.

I think you might want to check your biology; the cells in plants require oxygen to produce energy, the same way animal cells do.
The difference, of course, is that plants can produce their own oxygen during the day using photosynthesis and, on earth, the amount of oxygen produced outweighs the amount of oxygen consumed but that is on earth.

The long and the short of it being you can't just dump plants in a CO2 rich environment and expect them to survive, which was my whole point.

"Plants also need oxygen"

You might be wrong there. Plants need CO2. The only "plants" which need oxygen are fungi and that's because they're fungi not actually plants.

.

Please read up on botany - several experiments have been done on plants in CO2 environments - mostly they can only survive in levels up to 25% - some plants die after being exposed to as little as 10%

Carbon dioxide (CO₂) is an important trace gas in Earth's atmosphere currently constituting about 0.04% (400 parts per million) of the atmosphere.

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The main component of the atmosphere of Mars is carbon dioxide (CO2) at 95.9%

no magnetosphere no party. sorry mates.

no magnetosphere no party. sorry mates.

Artificial magnetospheres?

I once read there is a simple solution, just let them dig an underground cave on mars or layer dirt onto the living quarters. The journey to get there will be the bigger problem.

One of the bigger reasons to live underground on mars is more to do with impact risk rather than solar radiation. The most logical choice seems to be using advanced probes that would go ahead of colonists and begin mine projects, collect and process metals on site, and then when the humans arrive they move into the tunnel systems built from mineral extraction.

Stuff that just makes a pretty light show on earth would be at risk of causing structural damage to a colony built on the surface, and also small enough to make it awkward to track reliably. So, digging in lets you kill two birds with one stone, three if you get a good mine yields out of the process as well.

"The difference, of course, is that plants can produce their own oxygen during the day using photosynthesis and, on earth, the amount of oxygen produced outweighs the amount of oxygen consumed but that is on earth."

Well -- why wouldn't that happen on Mars? There's plenty of light there.