Hacker News Reader

Comment by sgentle | Hacker News Reader

So, the argument is let's not go to Mars because we'd have to deal with cosmic rays. Instead, let's go to Titan, which has an atmosphere, but is ridiculously cold and rains methane. Also, we can't go there because it's nearly thirty times the distance. Plus we'd still have to deal with cosmic rays along the way.

I'm not convinced.

View on HN

Yup.

Frankly, if you can solve the cosmic ray problem for the journey to Titan, you also just solved it for colonizing Mars. Martian gravity is also closer to Earth's, so Mars still seems like the better fit in the immediate term.

Mars has way more sunlight (much closer to the sun and a much thinner atmosphere), which makes solar much easier. So equipment, supplies, and solar could be on the surface, and the radiation sensitive humans could be a few meters underground. As you mine for water you could dump the useless stuff on the surface and use the emptied space for living quarters.

Question is why live somewhere that's tougher than the top of MT Everest or either pole? Guess a population big enough to repopulate earth in case of an extinction level event would be a reasonable safeguard.

>Mars has way more sunlight (much closer to the sun and a much thinner atmosphere)

Mercury, Venus, Earth, then Mars.

(Mars is further from the sun and gets ~60% of our sunlight)

Mars vs Titan.

Ah, sorry, misunderstood.

But if you're only doing it to safeguard against extinction level events why not just set up multiple contingency populations underground here on this planet? They won't have to travel as far after the event.

I think the idea is to seed the extra planets BEFORE the ELE...

If an ELE hits, few would be around to make even that short trip to the bunker.

What kind of event is in your mind that gives people less than, say, an hour's notice?

Full scale nuclear war maybe? Much of the population would only have a few minutes notice at best.

Crazy as it sounds, full scale nuclear war is not an extinction level event. Catastrophic, no doubt, and might reduce the human population by a couple orders of magnitude -- but unlikely to kill off all the humans. There just aren't that many bombs (~17,000 is a high estimate) and the earth is really really big. "Nuclear winter" appears to be overdramatized in fiction.

There's quite a lot of semiserious discussion of exactly this question on the internet; this is just a rough paraphrase of the consensus. It can make for a fun couple hours googling.

How many does it have to kill to be an extinction level event? By the time we deal with the radiation sickness and the lack of civilization would we have enough people left for a breeding population?

I am not an expert in ELEs -- so I do not know... but I suspect if we are using that term, then its an event large enough to screw with the stability of all life populations on earth, thus I state that I doubt that people can evac in an hour - have you ever seen a city evac for a hurricane? let alone for an ELE? Yeah, they're all gunna die.

You misunderstand, I suggest creating a self reliant population actively living below ground (or at the bottom of the ocean). They have to be able to survive indefinitely without help from the surface, but so would a martian colony to weather an ELE.

Do these populations currently exist? Or are you suggesting we build them?

Have you looked into or thought about "breakaway civilization"?

I doubt such populations currently exist, though secrecy would be a requirement to defend against active attacks, so I suppose anything is possible. I'm also not necessarily suggesting we do this, but for those interested in colonizing other planets solely as insurance against major life impacting events on Earth it seems like this would be a more feasible near-term goal to achieve. It would also be an excellent test of the systems we'd need to deploy in the even more remote and hostile environments of other planets.

From my brief research, "breakaway civilization" is a keyword mostly associated with some extreme conspiracy theories concerning the Nazis and the inventions of Nikola Tesla?

I would say some nuclear submarines qualify.

The sad thing about the end of the cold war is that the governments are spending less resources on establishing such hidden underground societies

I love subs - they are awe-inspiring, amazing feats of engineering and terrifying weapons.

I highly recommend watching various documentaries on them. I think I have consumed every sub dock I could find online.

https://www.youtube.com/watch?v=wHIS1I9tv78 is a great one. Also, note that the engineering needed to make the Global Explorer was new and significant. I think that with the making of that ship, the CIA gained a lot of know-how for sea-ops, which likely played at least a minor factor into their ability to make requirements/requests into the design of the Jimmy Carter sub, which is largely believed to be the sub they use to splice undersea cables/or cut them...

https://en.wikipedia.org/wiki/Project_Azorian

All their surface infrastructure might not survive, whereas you do get that on Mars.

We could even call them Vaults and give them numbers!

I'm going to start saving up on bottle caps and water purifiers.

But people do live near the north pole. If the tech becomes cheap enough, a few people would live on Antarctica, as well (political boundaries and policies permitting).

If it's possible, a few people will go just about anywhere. Islands, deserts, mountains, poles...

Faced with the reality of living in a mine for the rest of their lives, no-one who is keen on colonising Mars would actually then sign up for it. Who would agree to basically imprison themselves on the off-chance of being the seed of a new humanity if the earth is made uninhabitable (an already unlikely proposition)?

Humans live in a ridiculous variety of environments as it is - an extinction event would have to be utterly catastrophic to wipe out all breeding populations.

.i na vacri la .mars. .u'i

> if you can solve the cosmic ray problem for the journey to Titan, you also just solved it for colonizing Mars.

Not necessarily, if the solution involves "go faster to reduce exposure". Going faster seems a lot more feasible than creating the appropriate protection.

Even if we find a way to go faster by a decent multiple, your looking at over a year of radiation exposure known to cause substantial brain damage. The shielding tech will still need to be researched... so might as well just stick to Mars

A penny sized hole in a space suit on Mars could mean a quick death. The lack of an atmosphere on Mars would make it exceedingly difficult to set up a colony there.

>A penny sized hole in a space suit on Mars could mean a quick death.

Also true for Titan (surface temperature -179 degrees Celsius).

thermodynamics isn't instant like that, and you'd be dressing in layers. It's much different than a hole in a pressurized suit

Mars has an atmosphere, it's just not breathable by any life form from Earth.

Here's how you solve the cosmic ray problem on Mars: put sandbags on the roof. Done.

It wasn't a proposal -- it was a thought experiment.

Let's do X is not a proposal?

No, that's the headline or title.

The final paragraph makes it pretty clear that it's really encouraging the readers to think about how precious our home planet is:

> There is no quick way to move off the Earth. We will have to solve our problems here.

Still trying to figure out why under the moon surface isn't an open topic for these guys. From there you could go to anywhere else. Other than travel time, the risks of Titan and Mars voyages should be the same, yes? Neither one has a realistic rescue option for the stay or duration of trip

The surface of the moon is dramatically more hostile than the surface of Mars by every metric, and it's almost as hard to get to the moon as it is to get to Mars. Building a long term permanent colony on the moon would be far more difficult than doing so on Mars.

As long as you can manage the travel, Mars is by far the more desirable target for colonization, both short term and long term. Elon Musk believes that his ITS can cut travel time down to 2-3 months, which seems reasonable, even if your craft's shielding isn't the greatest.

Can you give some examples for how the moon is more hostile? I've always thought that for both you need a pressure suit but that the temps and radiation numbers were similar? Sure it's 21 days of hot then 21 days of cold instead of 24.5 hours but that seems much easier to deal with than the communications delay and travel times?

The long days + nights pose problems beyond just temperatures. It means having to store a lot of energy to deal with the long nights, meaning either big batteries (heavy and hard to get out of Earth's gravity well) or nuclear reactors (riddled with political issues). The 24.5 hour days on Mars can easily be handled with small batteries, or if need be power generated by fuel extracted on Mars.

Gravity on the moon is also a big issue for long term habitation. It's only 16.7% of Earth's gravity, which is a far cry from Mars' 40% and is much more likely to cause physiological issues with the human body. 40% gravity may be enough for negative effects to be mostly offset by exercise, but 16.7% is much more doubtful. Crews would likely need to be regularly cycled, making it impossible for anybody to live on the moon permanently.

The surface of the moon is exposed to much higher levels of radiation by two counts: first, it's closer to the sun, and two, it has no atmosphere. Mars' surface radiation is a good deal lower thanks to extra distance and its atmosphere, as thin as it is, cuts down on that number significantly. Furthermore, with 24.5 hour days there are frequent breaks from exposure to solar radiation whereas moon colonists would be faced with 21 days of high exposure followed by 21 days of low exposure.

There's also the matter of resources. Raw material is both far more plentiful and more accessible on Mars; there's an atmosphere to pull gases from for oxygen and fuel and entire lakes of frozen water on Mars, whereas moon settlers would need to use expensive, complicated, and failure-prone machinery to process regolith. There are craters with some frozen water on the moon, but relying on those greatly limits the number of prospective colonization sites and will eventually be exhausted if population counts rise from outpost numbers to something more closely resembling a permanent colony.

There are other factors as well, but these four are some of the largest.

In addition to kitsunesoba's excellent answer, consider the potential hazards of lunar dust: https://www.sciencedaily.com/releases/2008/09/080924191552.h... .

That isn't to say that Martian dust won't be an issue, of course...but perhaps one that is slightly less problematic.

Hopefully we can develop some light materials for radiation protection. So we can have radiation-proof domes and suits on Mars.

I have to wonder if the recently discovered ice deposits on mars would do the job

https://www.nasa.gov/feature/jpl/mars-ice-deposit-holds-as-m...

If this really is just a metre down and 80% water it's got to be an attractive target - relatively easy to mine (once surface is cleared, just use heat) and a hollowed out underground structure with 1m of ice above would be an effective radiation shield:

http://space.stackexchange.com/a/1826

... and once you're there, water is water, plus water can be used to make fuel.

I'm wondering how contaminated are raw materials on planets without a solid magnetosphere. Could it be that most of the water out there is too radio-active for consumption?

Things get contaminated by radioactive material, not by radiation exposure [0]. And of course obligatory xkcd [1].

[0] https://www.mirion.com/introduction-to-radiation-safety/radi...

[1] https://what-if.xkcd.com/29/

So, your biggest problem in a reactor cooling pool is "lead poisoning", eh? :-)

Anyway, worth pointing out that cosmic rays are little groups of neutrons (and adjoining protons). I don't know about the half life of the resulting products, though, or how often a heavy nucleus collides with another nucleus, vs simply bashing through electron bonds.

The trouble there is that, in order to attenuate high-energy radiation like the cosmic rays under discussion, you need something that's either extremely dense or extremely thick, and ideally both - dense so a speeding particle is more likely to hit it instead of zipping past between the atoms, thick so that Bremsstrahlung X-rays get absorbed before they reach human tissue susceptible to ionization injury.

Both of these are physical necessities, and both militate directly against the idea of a light, comfortable radiation-proof suit or dome. They're also not something that can be solved by incremental improvements in materials science - as sensible to imagine that we're just an unknown number of iterations away from main battle tank armor with the mass and density of Styrofoam, and for precisely the same reasons.

I'm completely out of my depth here, but couldn't we develop some kind of force field to do this? I'm thinking something along the lines of a Faraday cage, but for the GCRs.

Is anyone researching this line of thought?

It might not be impossible, but we'll need to develop some new physics first.

A magnetic field (Van Allen belt, or analog on other bodies) deflects lighter charged particles better than heavier ones (with a greater mass-to-charge ration). E.g. - helium ions (alpha particles) vs iron nuclei as mentioned in the article.

Otherwise, pure mass over your head is the best defense.

Light materials are physically impossible (absorption shield will be heavy anyway), but some energy shield that will deflect radiation could be a solution both for colonies and for spaceships.

I would imagine that shielding a ship be easier than shielding an entire colony (unless of course one accepts the underground colony approach)

Also, the rad dose-rate on Mars is utterly harmless.

Reply on news.ycombinator.com