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  Suggesting that humans might find refuge on Mars after 
  messing up Earth is “ethically and technically absurd,” says 
  McKay. “I think we need to take the view that failure is not 
  an option. The notion of Mars as a lifeboat makes the Titanic 
  look like a happy ending.”
Much as I admire Musk's drive to not only explore but colonize Mars, I have to agree with this sentiment. Viewing Mars as a "backup" for Earth is like relying on the Commodore 64 in your closet as a backup in case your MacBook Pro gets fried.
Given the recent sentiment here you might think some people would prefer a c64 over a mbp.
I really need the D-sub game controller ports. Like I'm supposed to buy $50 of dongles just to hook my controllers up to a new computer? Ridiculous. I'm switching to C64 instead.
Humanity is not the only thing that can 'mess up' earth. If we had 10 years warning that a small rogue planitoid say 300 miles wide was going to hit earth we would not be able to stop it. Sure, this is an ultra low risk but having a backup is still useful.
Interesting point on the planetoid. You don't think in 10 years humanity could come up with some strategy to stop the impact?
Not even close. Picture a rock that could cover all of Virginia, DC, and Maryland at the same time and tall enough the ISS would hit it.
Honestly, that's sounding pretty good right now.
I'd be interested to see someone do the math, but I'd be curious how much energy it would take to deflect it by hitting it with nukes. It seems like if we could hit it 1 year out it would take well under 1 m/s to make it miss. How much energy that would take, I have no idea.
1m/s * 1 year = 31,556.926 kilometers considering the earth has gravity I don't think you could really go much lower than that unless it was really close to missing us in the first place.

https://en.wikipedia.org/wiki/Ceres_(dwarf_planet) is is a little smaller than that and estimated at 9 x 10^20 kg. So call it 10^21kg.

KE = 1/2 m * v^2 (mass in kg, v in m/s = joule) but a bomb is not 100% efficient call it 50%. So, 1/2 * 10^21 * 1^2 /50% = 10^21 joule.

Largest bomb ever detonated is = ~2.1×10^17 J so ~5,000 of them is kind of an ultra optimistic estimate. Not that we actually have 5,000 of them. Worse each of those weigh ~60,000 lb so we now need build rocks, and even build the infrastructure to build the rockets to get 300,000,000 kg out there not just LEO.

At a rough ballpark 1/2 the worlds GDP for 8 years is not going to get you there. Worse that 50% was crazy optimistic.

Forgot to respond, but nice analysis! Thanks! Interesting how it comes out to something definitely infeasible, but still in the approximate realm of the world's nuclear capability (~16k of various sizes exist today).

The rocketry there would seem to be the impossibly limiting factor.

No, because as he stated before, the thing is going to hit the Earth in 10 years. If you wait around for 10 years, it's already too late. A 300-mile-wide asteroid is huge, that's the size of a dwarf planet. At the last minute, you'd need an astronomical (literally) amount of energy to change its trajectory. Even if we learned of such an impactor today, we'd likely be screwed because our current tech just isn't capable of moving something that big enough, even with 10 years of advanced warning. (I might be wrong about this, but I doubt it; even exploding a whole bunch of giant nukes probably won't change its course enough.) Maybe if we had 100 years' notice, it'd be enough.

Technology will surely improve in 10 years, but the laws of physics won't. It takes energy to move mass, and lots of energy to move a huge mass. I really do not think we're going to invent warp fields in 10 years like they did in the ST:TNG episode with a de-powered Q and use that to magically reduce the mass of the asteroid.

If we had 10 years warning, we might be able to stop it. If we could get out to it while it was still very far from Earth, it might not take much energy to deflect it. This is why it's important to build systems to detect such objects, like the Sentinel mission from B612.

https://b612foundation.org/sentinel/

Asteroids are tiny in comparison. My example was ~125,000 times the mass of what killed the dinosaurs.
I don't know, humans are great at blowing stuff up. It's the long-effort over long timespan stuff we're terrible at.
Ceres, the biggest asteroid in the asteroid belt, is only 946 km in diameter, and there are only six larger than 300 km.[1]

Asteroids the size of 300 miles don't just appear out of nowhere. In order for them to hit Earth, they must be coming out of the deep space, and they have to hit Earth (radius 6371 km) out of a circle of radius 1 AU (150,000,000 km).

To put it into perspective, if we can observe one "hostile" asteroid from outside the solar system crossing the circle made by the Earth's orbit every ten years (Note: we've never observed anything like that in our history, and we would surely have detected such a thing with 20th century technology), it will take 10 * (1 AU / 6371)^2 = 5.5 billion years before one hits Earth, on average. By that time the sun will destroy us anyway.

I guess they are still more likely than a group of hostile jerk aliens sworn to exterminate humans once we set our foot on Mars, but not by a wide margin.

[1] https://en.wikipedia.org/wiki/List_of_exceptional_asteroids

I mostly agree with your point as I was mostly going for effect not real risk. Though the earths capture radios is much larger than 6371 km, and odds don't run out like that.

However, the larger point stands. Earth is not completely safe and we really can't protect it from everything.

>is like relying on the Commodore 64 in your closet as a backup in case your MacBook Pro gets fried.

It's a better backup plan than never using a computer ever again.

I think the point is that it's morally questionable to call it a "backup plan" as it it's actually viable. Mars is better than nothing and it's worth pursuing, but only with the understanding that maintaining and fixing Earth is a much higher priority.

It's sort of like the autopilot thing. You shouldn't call it autopilot unless you're ok with people thinking they don't need to worry about driving anymore, and you shouldn't call Mars a backup plan unless you're ok with people thinking they don't need to worry about Earth anymore, because Mars will be there if we ever need it.

Is this really the semantics "backup plan" has for many people? For me it's something that's very inferior to the, well, plan.
Yeah, if the backup plan was as good as the plan, it would just be the plan. :)
Mars is not just inferior, it is almost literally not an option. It might be someday, and that's why it's worth pursuing, but even in the forseeable future it would just be a horrible, suicidal backup plan for like a couple hundred people.

The context of the quote is a response to people who are really enthusiastic about actually being Mars colonists. "It’s a lot easier to imagine a few scientists spending a year or two at a small Martian research station, like the ones in Antarctica, than it is to imagine thousands of people emigrating permanently to a Martian metropolis."

Building a colony in a salt mine would be an easier backup plan than a Martian one. Maybe you need to scrub radiation and smallpox out of your air but at least you have air! Admittedly solar power would be off the table, but almost everything else is easier.
>you shouldn't call Mars a backup plan unless you're ok with people thinking they don't need to worry about Earth anymore, because Mars will be there if we ever need it.

That would make it plan A. Backup plans are for when the primary plan ends in failure. Obviously a tiny city scraping by on Mars by itself while billions die in WW3 is not the goal.

But would the knowledge that such a tiny city exists reduce the likelihood that mankind will collectively act to preserve earth (when that preservation is inconvenient, or even painful)?

After all...there's always Plan B, right?

It could also be a great live demonstration how nearly impossible it is to live without a functioning Earth-ecosystem around us. Especially if it doesn't work out exactly as planned.
Until we bioengineer better suited humans.
The idea that some astronauts would survive doesn't make me feel like condemning myself and billions of other people to death. But, I can't speak for everyone.
And I certainly agree with you; however, the "Plan B" narrative is strong - strong enough to potentially mobilize significant financial and engineering resources toward the cause. When the narrative states that "man must become a multi-planetary species" very few people are thinking that those extraterrestrial environments will be spartan, hostile, and (possibly) reliant on earth resources. They imagine Earth v2 - but better because science (fiction).

If we're need the public to change their behavior to preserve the habitability of this planet, then giving them excuses for inaction may not be productive.

Instead of a C64, more like a lump of quartz. Technically, the silicon is there...
I don't really understand this sentiment, on either side.

If we're able to set up a self-sustaining settlement on Mars, then we're going to be able to survive on Earth, no matter how badly we mess it up. Just build a bubble and pretend you're on Mars. Short of total thermonuclear war, it's hard to imagine any non-survivable world where we have that technology.

On the other hand, _someone_ building a backup colony on Mars because _someone else_ decides to get in a nuclear war doesn't sound unreasonable.

Plus, there are world ending scenarios outside our control. Meteors, volcanic activity, etc.

I don't think anyone disagrees that the more palatable option would be to keep Earth in good shape in perpetuity. However:

1. Cosmic-size bad stuff could happen, at a scale where we are powerless. "Think of the dinosaurs", etc.

2. "Thanks" to the continuous progress of science and technology, we are putting more and more power into the hands of the everyman. Wherein the sanity and the moral trustworthiness of the aforementioned everyman is on a bell curve just like everything else - meaning most people are fine, but it's guaranteed there are a few spectacularly bad apples somewhere in that pile. Think of Jim Jones with nukes, or tabletop biotech.

So, making Mars livable is important for the same reason why you have backups for your data - only even more so. You do have backups, don't you?

We should absolutely do both - protect the Earth, and settle Mars.

I can easily imagine huge disasters on Earth that kill 90+% of the population but even then Earth will still have a higher population and be more habitable than Mars. And I can imagine things that would wipe out humanity on Earth and Mars. But the range of disasters that would totally wipe out humanity on Earth while sparing Mars seems pretty narrow to me.
If the Sun goes supernova, sure, we are all toast regardless of whether we are on Earth or Mars or even Pluto. But that's relatively unlikely. On the other hand, a large enough asteroid impact could kill 99%+ of the Earth's population and leave Mars intact.

But even if it killed only 90%, think about what the remaining 10% would do. They would probably wage war on each other to grab whatever land and natural resources remain. Furthermore, civilization as a whole would severely regress technologically, as we would lose the vast majority of power plants, laboratories, factories, data centers, etc. We would find ourselves back in the Middle Ages.

Compared to that, a super high-tech stable Mars colony that has a population of 1,000 would have it pretty good. Sure, they would be living most of their lives under the surface, but so what?

I'm not sure why you think that survivors on Earth, struggling for survival in a barren wasteland, would be more likely to fall into war than the inhabitants of Mars, struggling for survival in a barren wasteland. Really both groups would be hanging on with limited labor and capital (generators, greenhouses, domes) in the midst of plentiful natural resources and that's the sort of situation that leads to raiding more than what you'd normally think of as warfare.

And I'm really not sure why you'd expect a Mars of 1,000 people would have more technology than an Earth with 100,000,000 left alive. A technological civilization like ours depends on a body of knowledge that's way too big to fit in one or 1000 people's heads. Maybe in the future we'll have advanced AI that lets us get around this but that'd render the whole discussion moot.

>>I'm not sure why you think that survivors on Earth, struggling for survival in a barren wasteland, would be more likely to fall into war than the inhabitants of Mars, struggling for survival in a barren wasteland.

A fully self-sufficient Mars colony would not, by definition, be "struggling for survival."

>> A technological civilization like ours depends on a body of knowledge that's way too big to fit in one or 1000 people's heads.

A fully self-sufficient Mars colony would have plenty of computers that can store data. In fact, since the goal of such a colony would be to act as Earth's backup, we would most likely have most of the Earth's combined knowledge stored in a large datacenter underneath the Martian surface.

On the other hand, the shockwave from an asteroid that wipes 90% of the population on Earth would also instantly fry most electronics and render most technology useless. Like I said, it would send civilization back a thousand years. Sure, we would still have the knowledge in people's brains, but it turns out knowledge can be forgotten, especially when not actively recalled by the brain. When all your scientists have to become farmers, it is not likely that humanity would be able to retain all the knowledge it has collected over the past millenia.

It seems the Sun will become a Red Giant and not go supernova according to calculations. That means the Earth would be burned but the 4th planet, Mars, should remain unscorched. So, on a long enough timeline we must escape the Earth anyway. Let's get a head start!
Point number 2 seems extra applicable on Mars - where the systems sustaining life will be even more fragile. Unless you believe that Mars will be populated in perpetuity by a superior culture/class of people whose "everyman" would never, ever be a spectacularly bad apple (cue Heinlein/Moon is a Harsh Mistress/Belter/libertarian fantasy drooling). To be clear, I'm arguing that it's a fantasy.
Sure. And files sitting on a disk, any disk, are forever under threat from random failure. But would you have only one copy of that file, or two copies on separate disks? And would you argue that it's pointless to have two copies, since simultaneous failures could still happen theoretically? If you do, I invite you to delete all your backups right now.

Same with people and planets.

This brings up an idea that I've been thinking about for a long time. If we are going to be able to travel between the stars, that means we are going to have access to a lot of energy. How are we going to deal with the destructive capability of that? Can we even get there without annihilating ourselves?
On what sort of timescale? I doubt it would be a viable option in our lifetime, yet someone has to take first steps.

Few hundred years from now people may appreciate the foresight.

I'm not clear that there's any good analog example that does the subject justice...Which is exactly why we should do it :)
> Failure is not an option

There's guaranteed gonna be a catastrophic event outside of our control on Earth given a large enough timescale, be it climate change consequences, glaciation, collision with large meteorite, fatal epidemy, etc etc.

Mars makes for a shitty backup plan, sure, but we can't pretend that the Earth is gonna last forever either. A shitty backup plan is still better than simply sitting on our ass and hoping that no natural catastrophes ever happen; taking good care of Earth is not enough on the long term.

"Failure is not an option" is not even in the same reality as "sitting on our ass". It is exactly the opposite.
Most of the things you mention would still leave the Earth way more habitable than Mars. It would really need to be at the rogue planetoid/gamma ray burst level extinction event rather then global warming or nuclear war.
By the time the colonization of mars is going to be an achievable reality all of those things would not be an issue.

Large impact protection and geo-engineering are considerably easier efforts than colonizing mars considering just how hostile the environment is (even the martian dust is extremely poisonous to humans).

You are effectively going to live on a planet with no effective atmosphere, no magnetic field, with extreme temperatures and plenty of natural hazards.

The level of geo-engineering required to build martian colony which is both self sustainable and could serve as a lifeboat for the human species is currently insurmountable, we haven't even sent a single living thing to mars, we haven't sent a single person, nor we returned them safely.

We have not studied the effect of long term exposure to the martian environment and we have virtually no clue on what is going to be required in practice to enable large number of humans to live there for eternity.

And most importantly everything on that list with the exception of a gamma ray burst (which would fry mars also) is going to live earth considerably more liveable and hospitable to humans. If you can build a self sustaining colony on Mars you can build on on earth even after a mega impact event, supervolcano, another ice age or extreme pollution.

Earth has an atmosphere that at best would require a rebreather, it has a magnetic shield that protects you from radiation, you won't die or suffer serious health effects because you were exposed to sand, and in any case the temperatures would still remain considerably more hospitable to humans than they'll ever be on mars.

Earth also has a diverse biome, which means regardless of what is going to happen life would still continue to exist in one shape or form, if nothing else this would constantly provide humanity with food, energy, and oxygen.

It seems to me we should be putting more effort into building very large space-based habitats. With a large space station, it can generate 1g artificial gravity simply by rotating (which is much better than Mars with only 1/3g), you don't have to worry about a hostile environment because it's entirely artificial so you can make it whatever you want, solar power should be abundant if you locate the station not too far from Earth (which will give you power and heat), so the only real problem will be radiation, but that could be mitigated with lots of shielding, once you've found a cheap place to mine for materials in space.

We already have small artificial environments here on Earth that people live in for extended periods; we call them "submarines". We also have the ISS and previous space stations, which people have inhabited for years at a time. So we know how to make artificial habitats which support life. Now we just need to scale them up a whole lot, make them rotate for gravity, and give them shielding since they won't be in LEO.

But why would you do that vs. just building a city in Antarctica or the Gobi Desert which is even more habitable? Outside of scientific research and tourism there just aren't a lot of reasons to go into space and neither of those require a huge colony of people.
Antarctica is NOT more habitable. It's really cold there, so you have to use a lot of energy to keep it warm. Space-based habitats don't have that problem, because there's no convective cooling like there is in Antarctica. They're relatively easy to keep at a comfortable temperature. The only thing Antarctica has going for it is a ready supply of breathable air, but supplying that hasn't been a big problem on space stations for a long time.

Also, a space station will have a much better view than an outpost in Antarctica.

A city in the Gobi desert would be pointless. First, it's owned by China and they aren't going to let you just build a city there, and second, we have tons of cities in deserts, so why would we want another one? There's no compelling reason to bother with such a thing.

More practically, it can be used for a lot of missions, like learning how to manufacture stuff in low-gravity (and taking advantage of low-g or zero-g for manufacturing) (the middle of the station would be zero-g), or acting as a waypoint for other missions to the Moon or asteroids or Mars, etc.

The main disadvantage to the huge space station is, of course, cost. But there's enormous economic opportunities there beyond tourism and research, starting with resource extraction.

Antartica has breathable air, gravity, a magnetic field, water, and much much cheaper to resupply and move heavy equipment too. Now I still wouldn't reccomend building a city there, or the Gobi desert both of which I agree would be pointless, it's just that a giant space station is even more pointless.
>it's just that a giant space station is even more pointless.

Sorry, but this comment is just plain ignorant. Would you also call the Apollo missions pointless? Building a giant space station would give us a permanent and significant presence in space, and would give us enormous advances in technology as we figure out how to deal with the challenges of such an engineering undertaking, just as we did with Apollo. Moreover, the station would have a lot of other uses, such as manufacturing. You can't do zero-g manufacturing in Antarctica. There's untold uses for low-g or zero-g manufacturing, perhaps things involving crystal growth. The station can also be a waypoint for asteroid capture missions, which would give us immense mineral wealth without having to do environmentally-horrible mining operations here on Earth.

> Much as I admire Musk's drive to not only explore but colonize Mars, I have to agree with this sentiment. Viewing Mars as a "backup" for Earth is like relying on the Commodore 64 in your closet as a backup in case your MacBook Pro gets fried.

I tend to agree about the "backup Earth" justification. But is there really any justification required, other than it's our human nature to want to explore and push the frontiers?

When people started moving from Europe to America in the 17th century, I don't think anyone saw it as a backup plan.

>When people started moving from Europe to America in the 17th century, I don't think anyone saw it as a backup plan.

i like the Mayflower crowd motivation, in particular "found the Dutch morals much too libertine."

https://en.wikipedia.org/wiki/Pilgrim_Fathers#Leiden

So, once the transportation to Mars starts working, one can imagine various new settlements by groups "special" in one way or another. Imagine an Amish colony under a giant glass dome for example.

I find it kind of funny imagining a group best known for their reluctance to use premodern technology colonizing Mars.
Musk's justification as he speaks it is a drastically simplified version of what he's really trying to say - instead of a lifeboat, or a backup, think of a Martian civilization as a technology development platform. All the stuff that they would have to come up with in order to survive, and eventually, thrive, would present a whole new class of advanced geoengineering and space technology that would be used on Earth and beyond.

And if you're thinking, "why not just develop that specific technology that we need and save the money of a whole Mars venture", thats not how development of real, usable tech works. There are many things that were developed for one use that were eventually used for something else. R&D is a complex web of different ideas and solutions to different problems.

Even if we don't realize all that we want to on Mars, the new booster system will open up many other options for Earth-based satellites that can be useful here and now [1]. Space science has been essential for studying climate change[2], and will continue to be in the future, even (and especially!) if that space tech extends to other planets.

1. http://www.antipope.org/charlie/blog-static/2016/09/what-els...

2. http://www.planetaryresources.com/earth-observation/#eo-intr...

The "other applications" are what I think most people miss, and what's really important. For example, a lot of people think asteroid mining and resource extraction will be huge. I am skeptical. Processing anything in zero gravity may prove to be intractable. I welcome anyone to ponder how to really actually mine an asteroid. In zero or near zero g, no earthly techniques work; pick axes, drills, etc. All new techniques will be required.

I think the Martian killer app may turn out to be a not too inhospital, shallow gravity well, that can serve as the industrial jumping off point and base for developing the rest of the solar system.

Another thing to note is that if we can survive on Mars, then we can just as easily do so on the moon Callisto or dwarf planet Ceres.
Colonizing Mars and "saving" Earth are not two opposed goals. You don't have to choose one or the other. You can do both. The problem I have with the argument proposed by McKay (and a lot of others) is that it's way too simplistic and misguided. It makes Mars colonization supporters like the ultimate pessimists, people who have already conceded the Earth battle to be lost. This is simply not true but it is implied by the argument.
Relying on Mars as a backup planet for humanity is more like relying on the Commodore 64 in your closet as a backup of last resort in case all other computing devices in existence are irreparably fried. The C64 may not be anywhere near as good as all those other devices but in the insanely remote chance of a catastrophe, having a terrible computing device is better than none at all (except in the case of Mars, we'll be wiped out without the backup with no chance of bootstrapping back to civilization).
just like the dinosaurs messed up earth when they all died too?

Such a stupid sentiment. Humans can be wiped out for a variety of unknown reasons. It's not necessarily that "we messed up."

We want to terraform mars, but we are marsforming earth instead. With many people still not accept climate change, things are going to get harder.

Not all ice on earth is water. Some of it is methane. Methane is a much more powerful greenhouse gas than carbon dioxide. Once the arctic permafrost containing methane starts melting, produces a strong greenhouse effect that raises temperatures, reinforcing the melting process by making it faster...

This is believed to be linked to the Permian Extinction event. In that sense, this would be an existential threat that needs to be managed carefully.

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

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

I'm guessing the downvotes are because nearly everyone on this website accepts the reality of climate change, and your comment doesn't seem that relevant.
Note that I also added some information about a very specific side effect of global warming, which is less often discussed.
Its already happening in the Russian tundra.

http://siberiantimes.com/ecology/casestudy/news/n0681-now-th...

"It's already happening"--um, you realize that "it's" been happening on this planet for millions of years, right? The climate changes, all over the world. Before humans, after humans.
Yes, but it is in our best interest to not accelerate the process, especially before we have figured out how deal with the side-effects.

Among the obvious side effect --raise in temperature-- the oceans starts absorbing carbon dioxide and methane becoming more acid, acid enough to for example erode the shells of snails.

Lots of natural processes are bad for humans. Evolution, extinctions, forest fires, floods, droughts, hurricanes, earthquakes, erosion, etc. All of these things happened before humans, and we still would sometimes like to stop them so that there is no "after humans". We don't need to save the planet, the planet will be fine, we need to save ourselves.
I don't accept the reality of any science performed in an echo chamber--I've been too close to people doing that research and I know that what motivates them is not ultimate truth. Take that for what you will.
What is your definition of echo chamber? Do you believe in evolution? Evolution is even more of an echo chamber, because there aren't any huge companies that will be ruined if it's true.

Also, does an echo chamber necessarily mean something is wrong?

"...what space can do to a human body could be a huge problem. “They’re going to be sick when they get there.”"

I see this time and time again, but nobody has given me a proper reason why we cannot send a spinning ship, one where zero-gravity wouldn't be an issue. Radiation is certainly a problem, but again that is a matter of shielding/weight. I don't see any monumental reason why we couldn't send perfectly healthy people. The only real issue seems one of cost.

It takes energy, have to design the ship to withstand the rotation, and it would have to have a pretty long radius (like 300+ meters). Almost certainly you wouldn't be at full gravity either, but like half. It adds a whole bunch of headaches that might not be worth it.
Rings are only one of many 'spinning' options. There is something to be said for two objects tethered by a long rope. Such a structure can spin and still reach 300+ meters with ease. And building such a thing in orbit is awkward, but not in the same league as constructing a 300m ring.
Cost is the monumental reason.

Start with a design that can produce 1G from spinning with a suitably gentle gravity gradient that people can live in it.

Then try to figure out how to accelerate that very large structure so it can get to Mars. (You can use the fuel as a radiation shield, since there will have to be a metric assload of it.)

"The only real issue seems one of cost."

But that is a real issue. A tiny ship is billions of dollars. A ship big enough to provide even half a G is more like a trillion dollars. It can't simply be a tiny spinning wheel. It has to be dozens of meters across.

Of course, trashing Iraq cost us over a trillion so far, and will likely exceed 2 trillion before all is done, but that's different.

(comment deleted)
Well, we can't even send a non-spinny ship full of people to Mars, so sending a ship that would be more complex, and much larger is out of the question, no?
The possibility of practical artificial "gravity" isn't the only reason that's a stupid argument. We regularly send people to the ISS for longer than it takes to get to Mars and they're fine. Sure, it takes them a few hours to fully re-adapt to gravity and a few months to regain their muscle mass, but they're not sick.
The trip to mars takes about 6 months (~180 days). Every single record in the table you linked is longer than that.
Ah, I guess I was assuming round-trip. Article mentioned 3 years as the likely shortest round-trip.

I suppose if we are talking about a one-way death trip then yea. Maybe some people will do that initially, but long-term you'd have to think our goal of reaching Mars would include being able to return.

Travel to Mars will be significantly different w.r.t. cosmic ray exposure:

"Exposures on the ISS average 150 mSv per year, although frequent crew rotations minimize individual risk. Astronauts on Apollo and Skylab missions received on average 1.2 mSv/day and 1.4 mSv/day respectively."

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

so the issue is reduced load on muscles and bones.

10x rate of bone resorption in osteoporosis. bones are the biggest worry imo.

even though the astros work out 15 hours a week, it's still not enough to cover this rate of resorption, and (this is an asspull) pretty sure it affects them for months or years after doing long stays at ISS.

I'm not sure if there's any proof that we could create artificial gravity such that these decreased loads wouldn't still occur. wouldn't it mess with their inner ear as well?

And yeah, the only real issue is cost, but that's a doozy of an issue. what country is going to spent monumental budgets on making this ship with all the financial crises going on currently?

>I'm not sure if there's any proof that we could create artificial gravity such that these decreased loads wouldn't still occur.

Acceleration is acceleration. Your body doesn't care whether it's coming from a big hunk of mass in the form of a planet, or from continuous rotation. Yes, artificial gravity will work just fine in completely eliminating the negative effects of microgravity on humans.

>wouldn't it mess with their inner ear as well?

Only if the diameter of the structure is too small. Then you get coriolis forces large enough to cause these side effects. Effectively, the "gravitational" force felt at your feel is smaller than what you feel at your head. And also, with a small diameter, you have to rotate the structure at a high rate to achieve 1g. With a sufficiently large station, these aren't a problem: the rotation is very slow (maybe 1 rpm) and the difference felt between your head and your feet is negligible. But building a large structure in space like that is difficult and costly and we haven't done it before. But now's a fine time to start....

>what country is going to spent monumental budgets on making this ship with all the financial crises going on currently?

That's the main problem, and it's entirely the fault of the political leadership in those countries, who are mismanaging resources and allowing corruption. George W Bush's Iraq war is a prime example of this: for the cost of that war, we could have built a rather nice space station.

Wasn't this solved by the vacuum weight set shown on smarter every day? They use a piston in a vacuum with an adjustable pivoting arm to produce consistent resistance (a spring will provide more resistance as it is compressed or stretched than in its rest state). I thought they were saying it was the first time some astronauts were returning home with higher muscle/bone density than when they went up.
My GP is big on bones, specializing in old people. He helped develop some of the fancy bone scanners decades ago. He told me that astronaut bone loss is a solved problem, that if they want too they can keep bones strong for a year or more. He was of the opinion that when astros come back with reduced bone it is because they have been part of a study. The goal isn't to save all the bone, but to study exactly how little exercise is needed to achieve satisfactory results.
That makes sense, easy to forget they are sometimes called on to be highly skilled/paid lab rats at times :)
If you cut the trip time down far enough, the need for artificial gravity is greatly diminished. Taking Musk's ITS/MCT plan as an example, the trip will take only 2-3 months and the destination (Mars) has 0.38 Earth gravity. In that situation, there should be little to no physiological issues and the astronauts should be more than strong enough to deal with Martian gravity levels upon arrival, especially if they exercise on the way over.

Mission plans that call for much slower travel (6+ months) are much more likely to cause trouble for the travelers, which in why in my opinion any plans that are seriously considered should minimize travel time as much as practically possible. The logistics in getting a craft into space, getting it spinning appropriately to produce artificial gravity, and hurling it towards Mars are significantly more complicated than, say, refueling in orbit to allow for reduced travel time.

In the article says the engineers said its a matter of adding too much complexity.

Also consider that its a few months trip (Scott Kelly did over a year) and the real problem is when they live there. Mars gravity is only 38% of earths. So the problem while slower, still will be an issue.

I think the discussion of the kinds of risks Mars might act as a hedge against are being trivialised a bit. It's not all just about asteroids. Elon has researched this pretty thoroughly. If you want to really understand what he's talking about look up Nick Bostrom, but here are a few.

* a nanotechnology disaster

* Implementation of technologies that enable a global super-stable oppressive state.

* An AI disaster along the lines of a paper clip optimiser

* An AI or augmented intelligence that deprecates all lesser intelligences.

* The film version of I Robot.

* Biotech plague.

* Regression to a stable social and biological state optimising for lower intelligence or stagnation.

The way I think about this is that it's not just a backup. It's also deliberately introduced variation in environment and social structures that variegated Hunan civilization. Well develop technologies and social structures we wouldn't otherwise have that might help mitigate some of these risks. Semi-isolated from Earth, it would be at least partially protected from many of these threats. Of course, it could introduce new threats, but the isolation would work to protect Earth to some extent in that eventuality.

https://en.m.wikipedia.org/w/index.php?title=Global_catastro...

Nick Bostrom's research costs £6.99. It is not a research, it is a quick way to make money while the window of opportunity is still open by doing cargo cult science.

I am yet to hear a decent argument about how AI will wipe out the earth. It starts to belong to the same category as politics, nobody knows what they are talking about, but everyone has an opinion. Even the so called "smarts". I remember there were news about Stephen Hawking being concerned about AI, if you watched his interview, he literally pointed his software to the "Existential risk from artificial general intelligence" wikipedia page and read the abstract... Elon Musk started by comparing AI danger to "The Terminator" scenario. Seriously a f* movie? How about we don't go to Mars because of the "Alien" movie? Now he says that "not all scenarios are benign..." - no shit, Scotty.

> I am yet to hear a decent argument about how AI will wipe out the earth.

I ask AI how to create a biological virus that would kill every human on the planet that's encrypted enough other AI would not be able to cure it in time.

I think you are on to something. You should really consider publishing this, just don't forget to add some graphs and equations. Hell, screw that, just package it as a book and start selling it for £6.99 a pop.
You seem to be somewhat confused. Bostrom is a philosopher, not a scientist.
> a nanotechnology disaster

This would also likely to affect mars.

> Implementation of technologies that enable a global super-stable oppressive state.

And what prevents them from just sending a few nukes to mars?

>An AI disaster along the lines of a paper clip optimiser

Mars and earth are going to share some form of a network, an AI disaster on earth is not likely to be contained to earth and vise versa.

>An AI or augmented intelligence that deprecates all lesser intelligences.

Same as the above, also what prevents that AI from building spaceships and exterminating the humans on mars?

>The film version of I Robot.

Again what prevents them from building spaceships of their own?

> Biotech plague.

Plagues cross oceans they can cross interstellar space also, it's unlikely that any sort of natural/unintentional release could be contained in an era in which interplanetary travel is a common occurrence, especially if people would seek refuge on Mars, and there is nothing stopping some death cult that releases a bioengineered plague intentionally from infecting mars also.

>Regression to a stable social and biological state optimising for lower intelligence or stagnation.

Again nothing about Mars implicitly provide protection against the stagnation of human culture or knowledge.

The point is simply any large scale disaster would either not be contained to a single planet, or would still leave earth a considerably more habitable place than Mars.

None of these reasons are of course a reason why we shouldn't go to Mars.

Mars is just the first step. The more environments we habitate (ceres, europa, titan, venus etc), the less the probability that they would all be affected by a disaster.
I addressed this in my post.

> Semi-isolated from Earth, it would be at least partially protected from many of these threats.

It introduces a significant time and space gap, a firewall between Part of human civilization and the rest of it. It's not a guaranteed solution, but I think it could give us a much better chance. I'll counter your line of challeng - how do you know for certain it won't help mitigate any of these risks?

You also seem not to have noticed my argument concerning introducing a source of variegation into our civilization that might help us cope with some of these threats better.

I can only imagine the feeling that those engineers got in the room the moment that rocket relanded on earth. Wish I could experience it
This article is one big downer. Being realistic is one thing, but this read more like a hit piece than anything else.
I just finished "The Dark Side of the Moon" by Gerard De Groot, which is a history of the American space program focused on the key people involved and their motivations.

The author argues that a major problem with the manned space program was that we had no rational need to send humans to space.

Was going to the moon about science? National defense? International relations and prestige? None of these arguments held up. (Most scientists hated the huge amount of tax money spent on manned space flight that could have been spent more efficiently. The case for sending people instead of robots was based more on fantasy than on reason.)

The story makes Eisenhower seem very wise (for trying to avoid getting into a pointless and wasteful race against the Russians and his awareness of how the military industrial complex would serve its own interests at the expense of the nation as a whole). It even points out that Kennedy was nowhere near as enthusiastic about the moon landing as you'd assume and regretted locking the nation into an expensive promise he couldn't get out of.

Quotes from astronauts who visited the moon portray it as "magnificent desolation":

The first thing that springs to mind is the vivid contrast between the Earth and the Moon... I'm sure that to a geologist the moon is a fascinating place, but this monotonous rock pile, this withered, Sun-seared peach pit out of my window offers absolutely no competition to the gem it orbits. Ah, the Earth, with its verdant valleys, its misty waterfalls... I'd just like to get our job done and get out of here. - Michael Collins, Apollo 11