It has an "atmosphere" It's 0.00628 atm according to Wikipedia. That's effectively a vacuum. You can't have liquid water on Mars.

So you can grow plants in some kind of transparent pressurized place... Just like on the Moon.. or on a space station

You can pressurize a chamber using the thin atmosphere, rather than being restricted to the gasses you bring with you.

You can use ISRU and atmosphere resource extraction to generate rocket fuel on the surface of mars, rather than being restricted to the rocket fuel you bring with you.

Ultimately, the answer is Mars has the necessary resources and when you look into the details just makes more sense and is easier.

You can produce fuel from lunar regolith as well.

http://www.wickmanspacecraft.com/lsp.html

But it's still much easier to grab even a thin gas than it is to mine anything. An extremely convenient source of both carbon and nitrogen is going to be a huge benefit in terms of trying for long term sustainability. The Moon does have plenty of oxygen in various minerals and hydrogen in the polar ice but you need more than that.

>That's effectively a vacuum.

That depends entirely on the effect in question.

You'd have a hard time pressurizing the moon's atmosphere to harvest it for propellent.

this effective vacuum gives a 10m column of water equivalent of radiation protection. you'll really like it compared to the moon.

To me, the 2 day vs 6 months commute outweigh that. Then again I haven't done the math.

In the long run, there should of course be settlements on both bodies.

When the pilgrims originally sailed to North America from England, it took on the order of two or three months. A six month trip to Mars seems reasonable in that context.

Yeah, but they went to fertile land.

A space colony would have much more need to get supplies from Earth.

Once we've learned how to run a space colony on the Moon, building a second one on Mars would be much easier.

The pilgrims didn't have to worry about being subjected to deadly cosmic radiation. They could also bring various tools with them and build habitats in their new home using readily-available materials, and grow food there from seeds (though they should have picked a more southerly landing spot...). They also didn't have to worry about having pressurized environmental suits just to walk around outside once they made landfall.

No, they just had to worry about weird diseases, storms destroying their boat en-route, not having any clue where they'd land or what the territory would be like, and being attacked and killed by angry natives. Oh and they were doing it all with pretty basic "science".

None of those problems exist on Mars. Others exist, but you can't just directly say it was easier.

The commute may be long, but at least there is an abundance of lanes.

Once you get there, what do you do? Just go back?

I assume different people do different things...

Tourism would be an obvious sustainable Moon industry. That does fit your description :)

How many tourists visit Admundsen-Scott, and what percentage of its operating costs do you think it covers?

Will it really be sustainable? How many people will want to go twice?

highest hike in our solar system - Olympus Mons!

What do people do on Earth? Live, thrive, expand, explore. All that stuff.

There are other important reasons for this that don't make such a great subject for a public presentation, such as getting away from Earth's political and military sphere of influence and achieving greater redundancy in case a large asteroid impact event happens on the Earth/Moon system.

> and is larger

I see this as a disadvantage; the major difficulty of space exploration is getting out of the Earth's gravity well. I don't think it's wise to fall back into another one.

Elon actually addressed this, you only need the booster from Earth. For all interesting targets the spacecraft can launch by itself and get back to Earth.

The point of the booster for Earth is both to get out of Earth's gravity well and through its atmosphere (both of which are far less of a problem on Mars).

What if that gravity well has the resources you need to get out of it?

The moon also has a small gravity well, but no real resources to help you escape it. Mars has a bit of a gravity well, but has many more resources to help you escape that gravity well.

Once you've solved dealing with Earth's gravity, Mars will be a cakewalk by comparison.

Mars has no magnetic field so you get cooked with radiation.

Mars' soil contains tons of perchlorate at levels which are very toxic to humans.

TBH Venus seems like a better candidate for long term terraforming.

You can build floating complexes in it's upper atmosphere, and it has enough oxygen and water locked in it's atmosphere and we might be able to fix the rotation and the density of the atmosphere in one go by using the atmosphere to speed up the rotation of Venus. While both of these are quite "far fetched" technically, as far as terraforming goes we aren't any closer to terraforming mars than Venus, and at least for Venus we don't need to figure out how to give it a magnetic field.

Venus also has no magnetic field. It has much stronger gravity as well, requiring larger rockets to take off from it, and it is quite difficult to mine resources from due to the high temperatures and pressures at the surface, meaning all materials for a colony would need to be sent from Earth.

Venus has an induced magnetic field which while isn't as good as what we got on Earth, is better than what you have on Mars.

https://en.wikipedia.org/wiki/Atmosphere_of_Venus#Induced_ma...

Additionally the current theory is that if Venus will be sped up to below 56h per rotation it would regenerate it's intrinsic magnetic field which should be near earth levels.

And while Venus does have higher gravity than Mars, it's still lower than Earth's, and overall the delta V for venus insertion orbit is slightly lower than what you need for Mars.

"Additionally the current theory is that if Venus will be sped up to below 56h per rotation it would regenerate it's intrinsic magnetic field which should be near earth levels."

That's great and all, but how exactly do we realistically speed up the rotation of a _planet_?

One of the more "probable" and more or less energy sane suggestions would be using mass drivers to eject the atmosphere at high speeds to induce spin.

The mass of the venusian atmosphere is high enough for this to actually work and still leave you a lot of atmosphere to work with, it will take 20-30 years but it still doable.

And pointing those canisters at Mars or the moon. Once you've hit Venusian escape velocity you might as well move that atmosphere somewhere else that needs it.

But compressing acidic gasses makes the corrosion problem worse, doesn't it? How do you deal with that?

Nothing says "I love you" like super-compressed canisters of acid hurtling through space at interplanetary speeds :)

I think you have a good candidate for the Portal 3 story line there.

A fleet of masses attached to solar sails imparting a little bit of momentum as each one passes by.

This is planetary engineering. It's not supposed to be fast.

Unless, of course, you are a Kardashev II civilization.

same way it actually slowed down: mess with the atmo.

Easier to live in Mars with some radiation and lower temperatures (and pressure) as opposed to 400C and acid rains of Venus

No one is suggesting living on the surface until it's terraformed, the dense atmosphere allows for easy construction of floating platforms.

As far as terraforming goes, Venus is just a better candidate for long term colonization.

oh ok, i'm 30 mins behind live.

> and is larger

Mars is much smaller than Earth. From Wikipedia: "Mars is less dense than Earth, having about 15% of Earth's volume and 11% of Earth's mass, resulting in about 38% of Earth's surface gravity."

See: https://en.wikipedia.org/wiki/Mars

Larger than the moon.

Parent was making a size comparison to the moon.

It's still much larger than the moon.

I wonder if the 1-way ticket to mars would appeal to older folks who can survive the trip, but don't have the physical strength for much adventure on earth.

Ref: Old man's war.

Nice idea, but I assume anyone recruiting for space travel is going to insist on people who are very fit and in 100% good health, which usually means fairly young people. Certainly there could be some older people, but probably not a majority.

Which is why the ISS is populated by PhDs in their 40s?

Of course you want the first colonists to not be sickly, but they won't need to be Olympic decathletes in their 20s. Equipment for lifting heavy objects can be sent more cheaply than people (it can go slowly and doesn't need life support).

I think for a venture like this maturity and patience is going to be more important than physical strength. There will be a lot of tedious tasks with long checklists that need to be followed near exactly to succeed. There will be a lot of disappointment and frustration when things fail or timelines slip. There will be the irritations of being stuck in a small social circle with a few people you intensely dislike but have to depend on for survival.

Add in the fact that your sperm or eggs will probably get exposed to large doses of radiation until they figure out how to get to Mars faster, and it will be far less attractive to anyone who is planning to have kids someday.

With substantially less gravity, you can lift 2.6x the weight as you can on earth. People in their 40-50s in good health with moderate strength, good maturity, advanced skills, and already-grown children are good candidates. And yes, with the radiation they'll get hit with, it's better than kids burning away their lives.

> There will be the irritations of being stuck in a small social circle

in my own personal experience, this thing works worse for older folks, who get territorial, grumpy and so on. But we aren't discussing folks in their 40s, rather 50s and 60s

And 97% of the land mass: http://www.wolframalpha.com/input/?i=mars+surface+area+%2F+e...