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Comment by jmyeet | Hacker News Reader

Sure let's continue unmanned exploration of Mars but manned exploration let alone colonization makes absolutely zero sense.

mars is nothing more than a further, more annoying version of the Moon. Similar gravity, less sunlight (ie further from the Sun), communication latency (~10 minutes vs 1.5 seconds), no magnetosphere (just like the Moon so you'll probably need to live underground) and just enough atmosphere to provide no benefits and be annoying (eg dust storms that obscure the Sun and blow dust all over your equipment).

The romantic view of living on an above-ground Martian city is no more realistic than Star Wars.

On a side note, laser propulsion is likely the means within reach of interstellar travel. If nuclear fusion is ever viable (and that's still an "if" not a "when") then it could be too. But if you accept that laser propulsion is the only or even just the best means of moving stuff around, it's further rason why a civilization will tend towards building a Dyson Swarm.

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The Moon has very little hydrogen, carbon and nitrogen, which Mars has in abundance. These are very important elements both for biology and chemistry. E.g. if you want to have a self-sufficient colony outside Earth, you could do it on Mars but not on the Moon.

Mars could be terraformed (in theory); the Moon never could.

With no magnetosphere would there even be a point to terraforming?

Terraforming is an engineering project on such a scale it's probably reasonable to assume advancements like radiation resistance/repair in humans and artificial magnetic fields. For example, this apparently feasible (but currently batshit crazy) proposal: https://www.universetoday.com/153368/an-absolutely-bonkers-p...

Maintaining an atmosphere is a lot easier than creating it in the first place, and can use the same process and machines. In other words just live with the slow loss and replace the loss gradually.

I think what I meant is with no magnetosphere we would all die of radiation exposure regardless if there was a terraformed atmosphere or not. Without a magnetosphere we'd all be living underground anyway, no point in terraforming.

A strategically placed powerful magnet outside Mars can protect from the solar wind. There is an orbit that places the orbiting body always on the line between Mars and Sun. Place a superconducting magnet there that generates a few Tesla. Due to the distance from the planet, even though the magnet will deflect more distant particles to relatively small angles, this should still be enough to keep Mars completely in the "shadow".

Of course you'll have to and solar-powered thrusters to keep it on the orbit, and fly regular missions to replenish fuel in the ion drives. But thil looks doable even with today's level of technology, given enough money.

The ‘intuitive’ strategy of building a compact electromagnet and placing it between Mars and the Sun at the first Lagrange point is unfeasible. The most feasible design is to encircle or wrap Mars at the equator with a superconducting wire loop. The resulting wire diameter could be as small as ∼5 cm. With this design, the magnetic shield would have a mass of ∼10^12 g and would require mining ∼10^18 g, or only 0.1% of Olympus Mons. https://arxiv.org/pdf/2006.05546.pdf

> The Moon has very little hydrogen,

That's not quite true. The Moon definitely has polar ice but it also likely has more water than that [1][2]. Nitrogen seems only to be present in trace quantities [3].

> Mars could be terraformed (in theory); the Moon never could.

Yes and no (on both). People who make this claim often don't understand the magnitude of what they're claiming. Here's just one perspective: molecular velocities in the atmosphere are (of course) a Boltzmann distribution. As such a small percentage of those particles achieve escape velocity and fly off into space (called the Jeans escape energy) in exactly the same way that liquid water cools by evaporation. That amounts to around one million tonnes per year.

Mars has a lower gravity so the loss would be greater at Earth atmospheric pressure and that's just the loss you need to account for and gas that you need to manufacture or produce. Earth's atmosphere has a mass of ~5x10^18 kg. The scale of producing this just in terms of energy consumption is insanely massive.

So when you're talking about this level of energy expenditure it doesn't really matter all that much if you do it on the Moon or Mars.

But what's more, terraforming would necessarily be extremely violent. Do it too fast and you cook the planet. The likely way of getting what you need there is by impacting large bodies from space into the Moon. You probably don't want to live there while doing that. The timescales are likely to be in the thousands of years.

[1]: https://www.nasa.gov/press-release/nasa-s-sofia-discovers-wa...

[2]: https://www.planetary.org/articles/water-on-the-moon-guide

[3]: https://en.wikipedia.org/wiki/Geology_of_the_Moon#Elemental_...

> mars is nothing more than a further, more annoying version of the Moon.

I would say the opposite. Compared to the Moon, Mars has:

- A day-night cycle more suited to humans that’s nearly identical to that of Earth (Moon colonies will need to be in polar areas to avoid long stretches of no sunlight)

- A more temperate climate with less dramatic temperature swings

- Gravity likely high enough for most processes and machines developed on Earth to work correctly

- No sharp, statically charged regolith

- An abundant, readily available source of Co2 for use in production of fuel, oxygen, and other materials

The primary downside is longer transit time, but that can be overcome with smart planning and could be seen as a boon in the long run since it’s a forcing factor in developing self-sustainability — moon colonies will likely remain Earth-dependent for much longer than they need to simply due to how convenient it is to get things shipped from Earth.

Another downside of Mars is its having relatively less sunlight. You'll need quite significantly more solar panels to harvest enough power.

Even if Mars has enough uranium and thorium, it'll be quite a long time before mining and enriching it would be locally possible so as to power a nuclear reactor. Local production of solar panels looks a bit more feasible.

With this mindset we won't get very far as a species. It was probably already a mistake to climb down from the trees, right? But seriously, what else we should do as humans? I just can't imagine we will sit on our asses because that's a reasonable thing to do.

If the benefits of going to Mars only results in a new generation of humans to fall in love with space, that's already good enough.

Also don't forget all the cool technology that will spin off from this endeavour.

Being able to afford human space exploration is a really good sign since that indicates that we don't have any limiting factors to hold us back. The reverse scenario is way more depressing.

> With this mindset we won't get very far as a species.

I assume you're saying this in good faith but it's really a straw man argument because it's a false dichotomy. For one there's the obvious: I'm not saying "go nowhere". I'm saying "the Moon makes more sense to colonize than Mars". Also, that doesn't preclude ever colonizing Mars. A Moon-first policy just makes way more sense.

Another flaw: why do we even need to colonize a planet? It actually doesn't make much sense if you really think about it. I'm firmly in the camp that thinks humanity's future is in a cloud of orbitals aka an eventual Dyson Swarm.

It's way more efficient in terms of living area pre unit mass. It requires no energy tech more sophisticated than solar power. It requires no material that we don't already have. You don't have all the problems with getting into and out of large gravity wells. Gravity (ie spin gravity) can be exactly Earth normal.

> Another flaw: why do we even need to colonize a planet? It actually doesn't make much sense if you really think about it. I'm firmly in the camp that thinks humanity's future is in a cloud of orbitals aka an eventual Dyson Swarm.

It seems odd to quibble about which rock we should colonize when you think this far ahead.

Any species that lives in a "cloud of orbitals" or a "Dyson Swarm" is going to have colonized other planets in its solar system, if only as a temporary experiment. The thing to do now is push farther out and explore. Any rock will do but Mars has more romance to it and, for better or worse, that's a requirement.

I reacted to "colonisation makes absolutely zero sense" which is also a stretch.

I agree that a Moon colony makes sense, but I think both will happen. What we must see is that our future will take parallel evolutionary paths and that will involve colonisation of planets too, whatever that means. Why not have a permanent settlement on Mars? We have people living in the harshest environments already. It will probably be a good exercise to learn our limits. Maybe we can't have healthy, viable offsprings on Mars and we will settle with cloud cities on Venus.

It's probably not the best idea to pick a winning scenario, let's try everything till we can.

I think that yeah, in the long term, humanity’s future in space is in human-made crafts.

That’s a long way down the road, though. Before that, we need to develop a huge amount of infrastructure in space, and doing that will be extremely expensive so long as we have to fight Earth’s gravity well to do so (even accounting for things like cheap reusable rockets).

Either the moon or mars could serve as the “stepping stone”, but I think Mars is better situated for that due to having a wider variety of raw resources available and being overall less harsh than the moon while also having a dramatically weaker gravity well and practically nonexistent (aerodynamically speaking) atmosphere that would allow launching of vastly larger and oddly shaped crafts into orbit. From there, it’s much more feasible to start looking into mining asteroids and building city-ships.

The fundamental problem is if you need to live underground in self-sustaining terrarium environments there is plenty of land to do that on Earth. No need to add an expensive and difficult spaceflight on top of your problems. Not to mention completely eliminating a huge safety factor you enjoy from doing this on Earth.

Ultimately: what does Mars offer that you can't get on Earth or the Moon? Is it worth the extra trillions of dollars worth of expense and effort? Even if you're talking about surviving dinosaur-killing asteroid impacts the subterranian or subsea self contained colony offers many advantages over an offworld colony.

Gravity is higher, which is important for Humans. Also the resources are more diverse. And you can study Mars better from the surface of Mars than from the surface of the Moon (duh...).

I'm not a massive fan of Mars colonization. But I do get the appeal of getting manned missions there. Some science really can't be done as well or cheaply by robots alone. Though even with Humans on board, much of the work will be done by robots anyway.

> Some science really can't be done as well or cheaply by robots alone.

I'm struggling to imagine how a "lab full of equipment, life support, beds, bathrooms, comms, and return rocketry" doesn't ($-wise) translate much better to "many, many more teleoperated robots with miniaturized labs operated from orbit or Earth with frequent sample return round-trips".

Boots on the ground is a moral victory, but I don't see the science victory until you get enough equipment / personnel there to get a thriving ecosystem of thought in-situ. Not to mention: Astronauts are rarely the scientists that study the place they are going.

Now an ISS around Mars? That makes a lot of sense to me.

Humans can get a lot more work done, just by their dexterity, flexibility and ability to learn and adapt. For robots, even simple tasks have to be pre-planned, in this case sometimes years in advance.

It is conceivable that you could build a robot/machine that can collect one type of sample and do one type of analysis cheaper and quicker than a Human. However, human astronauts can do multiple types of these, maybe even adapt them on the fly.

for this, teleoperation from orbit seems reasonable. It's not been tried however.

Mars has water and more “acceptable” temperatures, I believe. This doesn’t have to be a mutually exclusive endeavor. We can put a base on Luna and colonize Mars. Maybe the Moon is the stepping stone to Mars?

This doesn't answer the question of why you'd want to put people on Mars in the first place.

Disaster recovery, the penultimate in off-site backups of humanity itself.

If that really is your goal then build a colony at the bottom of the ocean or deep under ground here on Earth - at sufficient depth there is literally nothing that could endanger such colony, it's functionally equivalent to being on mars without the idiotic travel cost.

Just put the DC backup in that rack in the corner, should be all we need.

Plausible, but I remember when I did my degree, one of the examples given about the importance of choosing a good site for “off site backups” was a company whose main site was one of the WTO twin towers, whose off site was the the other tower on the grounds that they couldn’t conceive of anything that would affect both without also destroying civilisation as a whole.

Well sure, but that's always a question of what are you trying to defend yourself against(what kind of scenario is the backup helping with). Twin towers are probably good enough for any kind of fire/electrical failure/theft/vandalism, but not for a meteor strike, war or as we've seen - terrorism. It's not that people in your example were stupid and didn't see it - just that most likely they didn't consider those dangers as important to have a backup for(if a war breaks out or a meteor strikes New York you probably have bigger problems).

It's the same here - most of the "human extinction"-scale events really don't touch a base that's 10km under water or under ground. Nuclear war or meteor strike? nope. Earthquakes? There are places safe from that. Solar flares? Nope. Deadly virus? Quarantine everyone arriving like you would with the journey to Mars.

Terrorism remains the main risk, but it would have been the same risk on Mars too.

And most importantly - it teaches us how to run an independent colony deep underground, which is important because despite all the Sci-Fi films showing us otherwise, the base on Mars would really have to be underground because of radiation risk.

So yeah, sure, run an underground base for a few decades then you can just transplant the technology to Mars - don't start with Mars first.

> don't start with Mars first

On that part we definitely both agree :)

Although, I would say that developing the tech to colonise Mars can be a useful rallying point for tech useful to Earth (if you can put a city of a million on the red planet, you can also put it in the middle of the Himalayas or Antarctica or the Sahara), in the same way that Tesla is useful as a rallying point for electric cars despite all the people I hear complaining about the build quality.

Except 8 billion starving desperate people trying to get it.

For instance if people were starving or hiding from fallout, those doomsday shelters the rich are building for themselves would likely be overran by the locals who helped build them or heard all about them from town gossip.

How are those 8 billion starving people getting into a base 10km below the surface of the ocean which requires a specialized submarine to get to? How is this any more realistic than 8 billion starving people getting to Mars?

And finally - I hope you aren't suggesting that the base on Mars is a way to escape "8 billion starving people".

You don't have to get to it to affect it. Eight billion very pissed off people can probably figure out how to drop rocks on the rich billionaire haven in an ocean trench.

A few of those people getting access to a submarine or just building a robot to go down there is a lot more likely than them building a vehicle and equipment to land on Mars and assault the habitat there.

I think we're talking about different kinds of scale here. A habitat that could be destroyed by "a few people building a submarine" isn't a backup policy for humanity. Not here, not on Mars, not anywhere. I'm imagining a proper city-sized habitation for few million people - with industry and agriculture to support it. A truly separate colony that trades with the rest of Earth when it needs to, but can survive on its own.

Also I really don't like how the arguments so far are about preventing the starving people from coming over and messing things up. It strikes me as very "we need to keep the pleb out" kind of thinking, no different than what some rich people are doing.

I can think of some things that would require them to stay there, unable to surface, for thousands of years. Having the ability to mine asteroids and create additional colonies and space stations seems better to me.

....just mine around your base? Create tunnels that span the entire planet if you must? How is all of this not easier than something as exotic as asteroid mining?

Even if the entire surface is irradiated(somehow) you can still launch things into space with underground railguns. It's not what we currently use, but it's easier to imagine this than building a base on Mars with current(or near future) technology.

Wouldn't earthquakes and even volcanoes still be an issue? I also imagine being at the bottom of the Gulf of Mexico was of no help when the dinosaur-killing asteroid hit.

Plus where does your energy come from? You don't have solar. You need to make your own light to grow food. Geothermal is possible I guess but the ocean is terrible for corrosion and building. The high pressure at the bottom of the ocean makes everything worse.

What's the ultimate, then?

Interstellar

Heck yes

With a "humanity" like this, maybe a bad idea... Maybe fix some of the bugs first with that money? Mars does not run away, you know...

Mars might not, but the technological/resource window of our civilization could. And we should not risk it.

We're better off riding it out in a bunker or something on earth. It's easier to build something self sustaining on earth that can survive anything, than build the same thing anywhere else.

We can do both. Even Musk’s plan is aiming at 10s of hours of 2020 global GDP spread over the best part of a century.

Why do anything?

This is a very flippant comment, but I will try to respond anyway - we simply haven't achieved a post scarcity society yet. Maybe we will at some point, but we just aren't there yet. So right now our time, money and natural resources are quite simply limited. So maybe it's not that we shouldn't have a base on Mars - it's just that maybe that shouldn't be the first step in human habitation in space.

What about motivating humans to strive for greatness? Being curmudgeon underground mole people sounds a lot less likely to inspire the next generation to strive to excel at STEM education. I think even just trying to colonize mars could inspire tens of millions of the next generation when they look up at the sky. A large majority of those won't go into the space colonization field and most will instead contribute to improving our lot and maybe even attempting to get to a post scarcity society.

I genuinely had a good laugh at the idea that simply by building an underground colony, the inhabitants would become "curmudgeon underground mole people".

I would personally love such a habitat, and would market it as a Safe Space for The Curmudgeonly(TM).

I don't see how it's any different than the parent comment in terms of being flippant. Should one meet any thing that humans may strive for with "why do that if we haven't done X first"? Why start a new startup if you haven't solved post-scarcity society?

We don't need to have a post-scarcity society before progressing science and technology by trying to and succeeding in colonizing Mars. Similarly we create plenty of technology while also not solving the post-scarcity "problem". Adding more resources or more people to solving a problem doesn't mean that it makes the problem easier or more likely to be solved. So you're creating this idea that we can't do X until we've done Y, when the truth is we can do X and Y.

Strategically I think we should create an international moon base first before going to Mars, but we can do both.

How long do you think until we can set up a base on Mars? Let alone other planets in the Solar system? 50 years, 100 years at the very least. If we don’t get started now, when will be the right time?

We flew to the Moon 50 years ago, logically there would have been human on Mars by now. That didn’t happen, so the next best time is as soon as possible. Like now.

As for limited resources, how much money do you think we spend for space exploration? We waste a lot more money and resource for other things. We should cut down those instead. Let’s take a trivial example. Do you think gaming is a waste of resource? Why don’t we cut down gaming?

That's not my point, I think either I didn't explain myself properly or people are missing it. What I want to say is that currently we have very limited resources(on the planetary scale) - no we don't have to wait for post scarcity to try, but I just don't understand why we're trying for Mars first instead of the moon, which is simply more achievable, cheaper, and fulfils all the goals of getting kids and adults excited about science again.

Why did Homo Erectus leave Africa? Why did early humans cross the land bring into the Americas? What could have possibly possessed the aborigines to cross the ocean to Australia?

Because its cool. Because its interesting. Because it is baked into our monkey brains to want to explore.

If people want to push the frontier, why are you such a grump about it?

I'm positively certain that in all of your examples people have pushed into new areas because of food, to find new land to live on, to find riches, to find the promised land or other mythological reasons. Somehow I don't imagine aborigines crossing the ocean because "it's cool".

You know what we're going to find on Mars? Rocks. A whole lot of radiation. No breathable atmosphere and freezing temperatures.

Imagine the most hellish place on Earth - that's still better for humans than the most pleasant place on Mars.

Would it be "cool" to stand on Mars? To stand on another planet? Of course it would. And I firmly believe that we should continue our planetary explanation - but making plans for human habitation on Mars when we haven't even been back to the Moon in 50+ years is literally just stupid. Put a base there, learn how to make it self sufficient and then let's talk about Mars.

Like if you could build something awesome on Mars it would pretty much universally be easier to build it in North Dakota.

Sure. It's easier to build in North Dakota than it is in the Swiss Alps, too, but people do that in part because they like the Alps.

There are going to be people for whom the idea of a frontier life in a place of natural, untouched beauty appeals. We've always had those folks. Some of them find life is harder than they expected; some thrive.

There has always been new opportunity at frontiers.

Mars is just harsher than anywhere on earth. There's less of everything other than space and harmful radiation (and you sort of have to make the space that you want/need when you get there...)

> I'm positively certain that in all of your examples people have pushed into new areas because of food, to find new land to live on, to find riches, to find the promised land or other mythological reasons

First of all, you can’t be positively certain of those. We don’t have access to the reasoning of why the Vikings decided to cross the Artic to America, or Polynesians crossing the Pacific.

Second of all, let’s say they did go to look for food. Are you sure they ran out of land to grow food, or forest for hunting that they had to look for new land? The answer is quite resounding no. Likewise, we don’t have to exhaust all of the resource on Earth before exploring other planets.

Finally, what were those mythological reasons you listed there, if not the desire of human being to explore?

>>Are you sure they ran out of land to grow food, or forest for hunting that they had to look for new land? The answer is quite resounding no.

The answer is an absolute and resounding yes, because that's exactly what hunter gatherers do - they move with the herds and where the food is. This isn't just an educated guess, we know this because there are still hunter tribes on Earth right now which do exactly this.

>>Finally, what were those mythological reasons you listed there, if not the desire of human being to explore?

We have historical records of entire tribes moving purely due to religious reasons, either believing that land somewhere else is sacred, or that the land they are on currently is condemned. If you think your deity lives over the horizon, then you get on your boat and go in that direction. Yes ultimately it's a desire to explore, but it's not just because it's "cool".

According to [1]:

> Temperatures on Mars average about -81 degrees F. However, temperatures range from around -220 degrees F. in the wintertime at the poles, to +70 degrees F. over the lower latitudes in the summer.

Bear in mind the atmosphere is <1% the pressure of Earth's, basically a vacuum. This actually means you'd barely feel 60mph winds (which, interestingly, was one of several flaws in The Martian book and movie) so hypothermia probably wouldn't be a huge issue from the air but still matters if you contact something solid.

It's unclear where the water on Mars is. It's definitely on the poles, which means you're at the lower end of that range, but there may also be water ice in more equatorial latitudes.

[1]: https://www.weather.gov/fsd/mars

Agreed, if an extinction level event happened on Earth, we'd be better off riding it out underground, than moving off planet.

I agree going to Mars is never going to be a useful for evacuation, but it could help if we where already there.

Most plausibility the long duration space flight should prevent the common cold from making the trip which would also prevent many hypothetical super plagues from doing so as well. In theory you could do the same on earth, but it’s unlikely for a self sustaining underground colony to consistently maintain that level of quarantine for new arrivals.

However getting a self sustaining population on Mars that could survive indefinitely is currently just science fiction and making the trip is the least difficult hurdle for changing this.

To be clear, off-planet colonization isn't an evacuation strategy. It's a continuation strategy in the event that humanity is wiped off the Earth.

You'd probably live underground if on mars anyway.

Earth obliteration is a certainty on a long enough timeline, before the Sun goes out. There's no question of riding things out underground at that point. We'd have to be elsewhere.

I strongly disagree and I dare say this is an incredibly short sighted view.

Pushing forward to living on Mars will unlock tons of technological and scientific advances that will only help us better live here on Earth, and Mars. The mother of invention will always been necessity. We simply don't need a lot of the tech that will be created, until we try to live off-world.

So much technology and scientific know-how, came out of the Apollo program when we pushed towards visiting the Moon.

This will be even greater when we move towards colonizing and living off-world rather than just visiting.

Let's accept this premise (which amounts to essentially "we don't know what we don't know") and I'll ask a natural follow up question: what is the difference between colonizing the Moon and colonizing Mars in terms of problems we'd need to solve and thus technology we'd likely gain?

The ISRU profiles of both bodies are significantly different and Mars has much higher gravity.

The Moon is, first and foremost, a weapons platform, and any every competent military sees it as such. There will never be a functioning colony on the Moon until the Earth is unified under a single government.

Mars is far enough away that colonization is possible, and the technology needs are so dramatic that we’ll have to develop a comprehensive deployment plan to bootstrap self-sufficiency from the start. Despite 150 years of industrialization on Earth, we still lack an experimentally tested plan to reboot.

> The Moon is, first and foremost, a weapons platform

This just isn't true. To quote Isaac Arthur, "there is no such thing as an unarmed spaceship". Kinetic energy is all the weapon you need.

Any colony on the Moon or Mars would need to be essentially self-sufficient from day one because the cost of getting payloads to eitehr are so vast to be uneconomical.

The Moon is the ultimate high ground in the Earth-Moon system. A mass driver that can fling rocks at the Earth is an extremely potent and easily maintained weapon. Much simpler than nukes. Could be remotely operated.

I think it really comes down to the distance. Mars is much further away. I believe the shortest one-way trip is 9 months (or maybe it's 2 years?) which means the colony/outpost must be 100% self-sustaining for at least that period of time. It will also require new technologies to make sure that humans can make the trip (sane and healthy) and that engineer products to last for that trip. Also, communication. We'll have to invent different communication procedures and technologies to support a colony on Mars. I think it'll also lead to new propulsion methods because eventually humans will want to make that trip go much faster. Of course the same can be said for the moon, but if the trip currently takes a few days you can only do it so much faster compared to how much more quickly you might be able to shorten a trip to Mars.

To summarize, many of the problems are similar but at much greater scales. I mean, hell we actually put people on the moon. No human has set foot on Mars.

My guess (and possibly hope) is cheap industrial scale deployments of Sabatier carbon capture.

I always thought the "but look at all the science we got out of it" line was rationalization. The Moon race happened because it was a contest. The reason I would buy for either Moon or Mars colonies would be access to resources in the belt.

In terms of fuel requirements, Mars and the Moon are about the same distance away, since Mars can utilize aerobraking and the moon has to use fuel to slow down.

> mars is nothing more than a further, more annoying version of the Moon.

This is simply wrong. Mars has had the geological processes necessary for ore formation. Whereas the Moon largely lacked those processes. Furthermore, Mars is rich in volatiles. It is likely Mars has everything needed to sustain human civilization. The issue is developing the extraction technologies and proving mineral reserves on Mars.

I also think Dyson swarms are the future. But I think the Mars effort is helpful towards getting there.

Elon's public motivation for Mars is basically a human backup plan. And for that, it probably may be the best shot of the next 100 years. It seems like a million people living and working on Mars is more likely to survive a worst case scenario that a million people in rotating space habitats.

But how is the Moon not a sufficicent backup plan?

How can a moon civilization support itself without the Earth?

The Moon has abundant iron and aluminium. Carbon and hydrogen are possibly an issue but capture a comet or two and that problem goes away. I'm not sure what the state of phosphorus is but luckily we don't need all that much of it.

What would we need from Earth? What would be economical to ship from Earth?

> but capture a comet or two and that problem goes away.

So the moon colony needs to be capable of making the things to go and capture a comet, and more comets in the future to replenish supplies, to support itself. That's a very large civilization.

The dust on the moon is extremely abrasive, the temperature fluctuations are more extreme, there is no atmosphere that provides protection against meteorites and high energy particles (not that mars has a thick atmosphere, but it is better than nothing), and the gravity of the moon would be a lot harder for humans to adjust to.

There is a future where some scarcely few people set foot on Mars and survive with a fleet of robots. The rest of us can experience Mars through virtually reality. I think this is a likely outcome.

Well stated!

Humans can be surprisingly useful still, even if we are very costly to maintain. https://en.wikipedia.org/wiki/Moravec%27s_paradox

I'm hopeful about artificial magnetic fields - modern superconducting magnets could do wonders in orbit with solar power.

Or here's sending ions from Phobos to do it: https://arxiv.org/abs/2111.06887

Even without superconductors.

If I was in change of a lunar colonisation plan, first thing I’d do is send up a rover with some limited ability to process lunar regolith — at a minimum into aluminium, preferably also PV. This rover would slowly crawl around the moon (doesn’t need to be the equator, but at least 5.14+6.68° from the poles to avoid being in darkness at the wrong time of year), leaving a fat conductor behind it. If the rover needs human interaction, it’s only a few seconds of light lag.

Once the processing has circumnavigated the moon, the conductor is already in a desiccated vacuum on non-conductive rock, so no extra insulation needed for that to be an HVDC line.

Then send some transformers and as much PV and industrial equipment as you want, because now the 14-day-long lunar night is easy to get through. The current going through the conductor gives you a free magnetosphere whose strength goes up the more PV is connected.

If you can’t build such a rover, you’re probably not ready to colonise the moon in the first place.

I don't disagree with your assessment of building aluminium conductors but my argument is that this isn't even really necessary. Living underground just makes so much more sense and is much, much easier. There is strong evidence of extinct lava tubes on the Moon. Sealing one of those up and pressurizing it is just so much easier, practical and incrementally scalable.

^This 1000x Almost nobody appreciates how truly inhospitable mars is. human technology is hundreds of years at the least from being able to live there sustainably, if it’s possible at all.

If terraforming is in the cards, stands to reason it would be first tried in our own backyard. Mars is the best contender for it. Actually it might be useful in other respects than being livable. The vision is far less romantic if you consider it a distant future project.

At least Venus has a magnetosphere. How are you going to terraform a planet that can't retain more than 6.5 millibars worth of atmosphere? Build a big-ass bubble around the planet to deflect solar wind? Nuke the core of the planet to re-melt it and get a magnetic field back?

Watch any of the videos on terraforming Venus by Isaac Arthur on YouTube.

A brief summary of proposed methods and their feasibility and a link to further literature may do a bit better at getting your point across than the name of a youtube channel that close to 0% of the people reading this are going to seek out at your say-so.

> a link to further literature

See above.

Nuking the core is neither sufficient nor necessary for the magnetosphere. Not sufficient because all of the nukes together are orders of magnitude too little to melt it, not necessary because a spinning ball of liquid metal is a really inefficient way to make a magnet.

IIRC one of the plans for an artificial magnetosphere for Mars only needed a 1 GW supply to the magnetic coil.

The core nuking thing I pulled out of my ass but I guess it sounds serious given a sufficiently fantastical context.

Doing a little more reading I came across the superconducting latitudinal "wrap the planet in a solenoid" thing, as well as magnets at L1 etc. I guess that's possible, but that's more of a 2000-years-out sort of set of ideas.

There's a philosophical debate to be had about how far out humans should be thinking when expending resources. If you build for tomorrow, you solve yesterday's problems. If you build for the next millenium, you solve nobody's problems.

> 2000-years-out sort of set of ideas.

Nah, if we really cared we could do either in like a decade or two depending on the Starship timeline.

> If you build for tomorrow, you solve yesterday's problems. If you build for the next millenium, you solve nobody's problems.

Essentially agree; this is why I don’t buy into longtermism: https://kitsunesoftware.wordpress.com/2020/01/08/morality-th...

If our species declared Total War Against The Lack of a Martian Magnetosphere, I could see that happening. However, that implies that our species are in a state of development and coordination that would largely obviate the existential need to create a "Planet B" as people imagine it.

Thanks for the link to the blog post, I enjoyed it.

Ya I think that we'll fail to make any measurable impact on global warming in our lifetimes, because it's much easier to sabotage movements than to invest in them. So we'll inevitably reach for a solution that's a sure thing, and the only one I know of that's scalable is a 1-10 atom thick sunshield at the L1 Lagrange point. It's a problem similar in scope to a light sail, so there's no mystery to it other than trying to grow the dang thing in space.

So if Earth gets a sunshield, it's no more difficult to grow one for Venus. Then eclipsing it and getting it to room temperature would only take a matter of weeks maybe? That would reduce the atmospheric pressure too. Seems like an orders of magnitude easier problem than waiting around for Mars to warm up and pressurize. Although on that note, we could build a giant reflector at the L2 point behind Mars to have room temperature immediately there too.

Looks like a solar sail can be as light as 0.00002 kg/m2, the Earth has a cross section of about 125 million km2, or 1.25e14 m2, so that's 2.5 billion kg or 2.5 million metric tons. Of course there's always a way to make a thinner sail, and we may not need to block all of the light, so I think a million metric tons is a reasonable estimate. Sounds like a lot, but a locomotive is 1000 metric tons, so 1000 train engines or 10,000 heavy launches to save Earth doesn't seem unreasonable. Also we probably only need 1% of that area to have a measurable effect on climate, and that way we wouldn't have to see the shadow either. So we're talking 10 train engines or 100 heavy launches.

https://en.wikipedia.org/wiki/Solar_sail#Materials

I'm not firmly in the terraforming camp, but something I'd like to point out is that humans don't need exactly 1 atm. About 0.5 atm would be sufficient. It's analogous to what is found in Bolivia's altiplano. Mar's gravity is sufficient to hold onto oxygen and nitrogen.

True, although if you've fixed the "atmosphere gets stripped away" problem, you've achieved the hard part.

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