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Old 8th July 2018, 04:37 PM   #161
smartcooky
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Originally Posted by Myriad View Post
"Less suitable for maintaining a biosphere, either through natural happenstance or by human artifice, that can sustain life based on the current global gene pool."
Fair enough. It makes no difference to my opinion though.

Originally Posted by Myriad View Post
Have you noticed that none of the earth's past planet-killing asteroid impacts have actually killed the planet?
Have you noticed that there weren't any humans around at the time, and that nothing mammalian bigger than small dogs survived the last one?

Originally Posted by Myriad View Post
An asteroid strike or nuclear war or Yellowstone eruption or other "extinction" event can change global conditions so that many, perhaps most, species can no longer survive. Mars gives you far worse than those changed conditions, right off the bat.
Why is that relevant? You are thinking surface conditions, I'm not.

Originally Posted by Myriad View Post
If you can create sustainable habitats with underground farms, power plants, a self-contained industrial base, robotic mines, and all that, to survive such extreme conditions on Mars, you can do it for a hundredth the cost on Earth. (One that actually gets hit by the asteroid won't survive, but you could build twenty with 20% of that Mars budget. I'd suggest scattering them around.)
You have some figures and costings to back that up?

Originally Posted by Myriad View Post
The only scenario for which Mars is a more secure alternative basket to put eggs is the long-term (500 million years) one, or a highly improbable strike by a dwarf-planet-sized impactor. There's no rush. And our current civilization is not ready for transplantation to Mars. It's not a workable model anywhere on any scale yet. Give us a few more cycles to work out the whole how-to-use-technology-sustainably thing.
I never said that, but if we, the human race, always used "we're not ready" as an excuse for doing nothing instead of exploring and spreading out, we would still be just be a couple of hundred thousand semi-intelligent ape-men living in an area of a few hundred thousand square kilometres in the vicinity of Olduvai Gorge.

Originally Posted by Myriad View Post
Guy McPherson's runaway rapid greenhouse warming scenario (and other similar ones) don't hold up to scrutiny. There's not enough carbon. All the carbon that's now in fossil fuels and methane hydrates etc. has been in the atmosphere before; it didn't warm the planet to 50°C then.
The science is far from settled on this.

https://www.technologyreview.com/s/4...fect-on-earth/

Even those climate scientists who don't think it is likely to happen are hedging their bets....

Goldblatt and Watson have an answer: “The good news is that almost all lines of evidence lead us to believe that it is unlikely to be possible, even in principle, to trigger full a runaway greenhouse by addition of noncondensible greenhouse gases such as carbon dioxide to the atmosphere.”

But there is an important caveat. Atmospheric physics is so complex that climate scientists have only a rudimentary understanding of how it works. For example, Goldblatt and Watson admit that the above conclusion takes no account of the role that clouds might play in this process.

And scientists’ ignorance of the processes at work raises a significant question mark. As Goldblatt and Watson put it: “Is there any missed physics or weak assumptions that have been made, which if corrected could mean that the runaway is a greater risk? We cannot answer this with the confidence which would make us feel comfortable.”

That’s something worth worrying about. What’s needed, of course, is a major effort to better understand the physics of warm moist atmospheres and something like this is indeed happening.

Goldblatt and Watson are sufficiently worried to suggest that we start thinking of mitigation strategies, should their reasoning turn out to be flawed. “In the event that our analysis is wrong, we would be left with the situation in which only geoengineering could save us,” they say


Its six years later.

Do climate scientists have a better understanding of the complexity of atmospheric science? No, they don't.

What mitigation has been done to reduce global warming? None, in fact, the fat pig in the White House has made things worse.

Originally Posted by Myriad View Post
As far as I can tell, what's going to happen is that all of the extractable fossil fuels will be burned; there will be severe climate change impacts which may or may not help push our civilization into collapse; the current mass extinction event will run to completion; humans will survive; and in geological time, the next couple of thousand years until the greenhouse gases weather out of the atmosphere will be an anomalous warm blip in a much longer term ongoing cooling trend.
Even this best case scenario does not sound at all pleasant for my grand-chlidren, and their children, and their children......

Originally Posted by Myriad View Post
Deep time perspective isn't easy. But it doesn't make sense to be planning for million-year and hundred-million-year scenarios, and then suddenly get all impatient about what's going to happen in the next few thousand.
It also makes no sense to bury your head in the sand and hope/pray/pretend it will all just go away. It won't.
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Old 8th July 2018, 06:31 PM   #162
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Originally Posted by Roboramma View Post
The issue is that he is making the argument that we may find ourselves currently within a window of opportunity in which we can colonize Mars that may be closed by some future event (a catastrophe, a decline, whatever it is), which suggests that we should do so while we can because that opportunity may be lost.

If that window is tens, hundreds, or even maybe if it's thousands of years it suggests that we should get started now. If it's hundreds of millions of years I think we can afford to wait.

I accept that there is some validity to an argument based on those shorter time frames, but that argument should not be conflated with one based on longer timeframes.

However, I think I misunderstood, and he is making an argument that includes both. The shorter time-frame limits our ability to colonize mars, while the longer timeframe is for the extinction of our species if we don't colonise mars within that shorter timeframe.

Did I get that right, cjameshuff?
In short, an event that greatly limits the probability of us leaving Earth is little different from one that immediately renders us extinct, when it comes to long term survival. There's a variety of possible events that could do so in short timeframes.

Establishing a sustainable presence in the rest of the solar system both directly improves the robustness of civilization on Earth against such disturbances, and allows it to be reestablished without reliance on the easily-exploitable energy and material resources that we had the first time around.
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Old 8th July 2018, 06:32 PM   #163
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Originally Posted by smartcooky View Post
Have you noticed that there weren't any humans around at the time, and that nothing mammalian bigger than small dogs survived the last one?

Why is that relevant? You are thinking surface conditions, I'm not. (Because humans, unlike most mammals larger than small dogs, can dig and build.)

Quote:
Why is that relevant? You are thinking surface conditions, I'm not.

Just trying to make sure we compare apples to apples.

Quote:
You have some figures and costings to back that up?

Sure. SpaceX's best projections for future costs (which far undercut all known competitors so far) for payload to low earth orbit is over $1500 per kilogram.

Now, LEO is still a very long way from Mars. My kilogram of payload has to get the rest of the way to Mars and then down to the surface intact. Do you agree that an additional 9x the delivery cost to LEO is an extremely conservative estimate of the cost for that?

Meanwhile, down here on this rock, I'm pretty sure I can have a kilogram of cargo delivered to practically any inhabited place on the globe for much less than $150.

Delivery of materiel is not the only cost, of course, but I'm at a loss to find significant cost areas that wouldn't have a comparable markup factor for Mars. Labor? Research, development, and design? Utilities? Communications? (Real estate costs and property taxes are the only ones I've thought of so far.)

Quote:
I never said that, but if we, the human race, always used "we're not ready" as an excuse for doing nothing instead of exploring and spreading out, we would still be just be a couple of hundred thousand semi-intelligent ape-men living in an area of a few hundred thousand square kilometres in the vicinity of Olduvai Gorge.

In difficult circumstances, doing something is not automatically better than not doing it. (That's one way to tell that the circumstances are difficult in the first place.) Rhetoric about how we would never have left the caves or crossed the oceans (all metaphorical, of course; humans never lived entirely in caves, and the first ocean crossings were most likely accidental) isn't always applicable. Neither "look before you leap" nor "he who hesitates is lost" are universally good advice.

Quote:
The science is far from settled on this.

https://www.technologyreview.com/s/4...fect-on-earth/

Even those climate scientists who don't think it is likely to happen are hedging their bets....

Goldblatt and Watson have an answer: “The good news is that almost all lines of evidence lead us to believe that it is unlikely to be possible, even in principle, to trigger full a runaway greenhouse by addition of noncondensible greenhouse gases such as carbon dioxide to the atmosphere.”

But there is an important caveat. Atmospheric physics is so complex that climate scientists have only a rudimentary understanding of how it works. For example, Goldblatt and Watson admit that the above conclusion takes no account of the role that clouds might play in this process.

And scientists’ ignorance of the processes at work raises a significant question mark. As Goldblatt and Watson put it: “Is there any missed physics or weak assumptions that have been made, which if corrected could mean that the runaway is a greater risk? We cannot answer this with the confidence which would make us feel comfortable.”

That’s something worth worrying about. What’s needed, of course, is a major effort to better understand the physics of warm moist atmospheres and something like this is indeed happening.

Goldblatt and Watson are sufficiently worried to suggest that we start thinking of mitigation strategies, should their reasoning turn out to be flawed. “In the event that our analysis is wrong, we would be left with the situation in which only geoengineering could save us,” they say


Its six years later.

Do climate scientists have a better understanding of the complexity of atmospheric science? No, they don't.

What mitigation has been done to reduce global warming? None, in fact, the fat pig in the White House has made things worse.

Since the system is complex and poorly understood, which makes predictions and modeling unreliable, we might consider other ways of estimating the extent of the effects. For instance, we could inquire whether comparable levels of greenhouse gases in the atmosphere have ever occurred before, and if so, what the climate effects were then.

Quote:
Even this best case scenario does not sound at all pleasant for my grand-chlidren, and their children, and their children......

No it doesn't. I'm truly sorry for that. If I could figure out how to do the Hari Seldon thing I would, but I know I can't change human nature or the laws of physics.

My search for productive responses has inspired some odd projects (perhaps taking the Hari Seldon example a bit too literally, how about a thumbnail-size fundamental 10,000-volume library on mask ROM? or maybe, designs for binary digital computing as a modular toy that can be made of wood or cardboard?) and led me into some strange company.

In any case, I don't see how a Mars colony helps in that time scale. It's fantastically unlikely that your grandchildren, or great or great-great grandchildren, would become Mars colonists. And if they did, they would likely face risks and privations every bit as severe if not more so.

Quote:
It also makes no sense to bury your head in the sand and hope/pray/pretend it will all just go away. It won't.

I agree.
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Old 8th July 2018, 06:48 PM   #164
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Originally Posted by Myriad View Post
If a high-tech civilization can't survive on a climate changed Earth (in the 50-200 years from now timeframe),

but only a high-tech civilization can survive on Mars,

and the climate on Mars is worse than that of a climate changed Earth,

then the logical conclusion is we're screwed. At least, within that timeframe.

But on Earth, we don't need high-tech civilization to survive, for the species to survive. Collapse, scatter, adapt, remember, and try again.
Your conclusion does not follow from your premise. Even if a Mars civilization wasn't likely to be mostly insensitive to climate, only climate shifts that simultaneously affected both Earth and Mars would threaten the existence of a civilization that has spread to both locations.

Relying on people surviving to "try again" is a poor substitute. Near-modern human populations have existed for millions of years. Behaviorally modern humanity has existed for ~50000 years. Humans eventually got around to building a complex technological civilization, but it's not inevitable. And doing it again, after all the most easily accessible deposits of ores and energy sources have been long exhausted, is far from a sure thing. And then there's the faulty assumption that the survivors will remember meaningful information about the events...
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Old 8th July 2018, 11:00 PM   #165
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Originally Posted by arthwollipot View Post
Of course I want to be pedantic. Have you even met me?

Genus is capitalised, species is not. Homo sapiens sapiens.



No, no NO!



It's 'Homo sapiens sapiens' not 'Homo sapiens sapiens'.


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Old 8th July 2018, 11:44 PM   #166
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Originally Posted by smartcooky View Post
Have you noticed that there weren't any humans around at the time, and that nothing mammalian bigger than small dogs survived the last one?
Small mammals survived because they could find shelter, such as burrows. We already have shelter, the ability to store water, food and fuel ... We're in a very different boat from those mammals. Projecting the effects of that event purely in terms of body size is absurd.

Originally Posted by smartcooky View Post
Why is that relevant? You are thinking surface conditions, I'm not.
An underground civilisation on Mars? Built using solar-powered excavators, cranes and so on? Most plans utilise sunlight to some extent for growing food. Will your farms be above ground?

Originally Posted by smartcooky View Post
You have some figures and costings to back that up?
You could shock us all to the core by providing some costings of your own one of these days; the costs that will be borne by private business, in your view. Putting a self-sustaining Mars civilisation underground just upped the cost by what, a hundredfold? More?
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Old 9th July 2018, 12:08 AM   #167
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Originally Posted by GlennB View Post
Small mammals survived because they could find shelter, such as burrows. We already have shelter, the ability to store water, food and fuel ... We're in a very different boat from those mammals. Projecting the effects of that event purely in terms of body size is absurd.
You're dodging

There were no humans 65 MYA

Originally Posted by GlennB View Post
An underground civilisation on Mars? Built using solar-powered excavators, cranes and so on? Most plans utilise sunlight to some extent for growing food. Will your farms be above ground?
A domed civilization. Perfectly feasible. Food grown efficiently indoors, perfectly feasible

Do you really imagine in your wildest dreams that you have found the killer blow that a bunch of scientists and engineers way smarter than anyone here, have all failed to notice?

Originally Posted by GlennB View Post
You could shock us all to the core by providing some costings of your own one of these days; the costs that will be borne by private business, in your view. Putting a self-sustaining Mars civilisation underground just upped the cost by what, a hundredfold? More?
I'm smart enough to never claim that "this" is more or less expensive than "that". No claim about costing = no need to back up the claim.
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Old 9th July 2018, 12:29 AM   #168
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Originally Posted by smartcooky View Post
You're dodging

There were no humans 65 MYA
Exactly my point, so where's the dodge? If a similiar thing happened now many humans would survive with ease for the reasons I gave. With a reasonable period of notice millions would survive. We're much more able to survive than those burrowing animals.

Originally Posted by smartcooky View Post
A domed civilization. Perfectly feasible. Food grown efficiently indoors, perfectly feasible
Pressurised domes that let through light but cut out harmful radiation? The heat losses will be vast. The kind of minor incoming rock that would burn up in Earth's atmosphere will punch a nice hole in it. Will the metal-smelting and other heavy industries operate within the domes?

You're making this up as you go along, aren't you?

Originally Posted by smartcooky View Post
Do you really imagine in your wildest dreams that you have found the killer blow that a bunch of scientists and engineers way smarter than anyone here, have all failed to notice?
The last argument of a scoundrel. "Elon Musk is smart and successful, so shut up and accept everything ever proposed by smart people, however wild and ill-considered they might be". Show us a plausible plan for a self-sustaining colony that gets mainstream scientific backing and we'll take it from there.

Originally Posted by smartcooky View Post
I'm smart enough to never claim that "this" is more or less expensive than "that". No claim about costing = no need to back up the claim.
That makes no sense.
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Old 9th July 2018, 01:17 AM   #169
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Originally Posted by GlennB View Post
Exactly my point, so where's the dodge? If a similiar thing happened now many humans would survive with ease for the reasons I gave. With a reasonable period of notice millions would survive. We're much more able to survive than those burrowing animals.
Another dodge. Are you saying that human civilization is 100% certain to survive another Chicxulub impactor type event intact?

Originally Posted by GlennB View Post
Pressurised domes that let through light but cut out harmful radiation? The heat losses will be vast.
Don't know much about greenhouses do you?

Originally Posted by GlennB View Post
The heat losses will be vast. The kind of minor incoming rock that would burn up in Earth's atmosphere will punch a nice hole in it.
OH MY GOD THE ISS COULD BE HIT BY METEORS AND ALL THE AIR COULD ESCAPE AND THE ASTRONAUTS COULD DIE.... Oh wait, it has... and it didn't, and they didn't.

Oh well.

Originally Posted by GlennB View Post
the metal-smelting and other heavy industries operate within the domes?
Why not?

Originally Posted by GlennB View Post
You're making this up as you go along, aren't you?
Nope

https://www.newscientist.com/article...lasts-forever/

https://www.nasa.gov/press-release/n...ourney-to-mars

http://www.americaspace.com/2015/05/...on-red-planet/

https://lockheedmartin.com/en-us/pro...base-camp.html

https://www.gizmodo.com.au/2018/01/n...for-mars-base/

https://www.space.com/33123-nasa-hum...pt-images.html

this is just a small sample... i do a LOT of reading and research

Originally Posted by GlennB View Post
The last argument of a scoundrel. "Elon Musk is smart and successful, so shut up and accept everything ever proposed by smart people, however wild and ill-considered they might be". Show us a plausible plan for a self-sustaining colony that gets mainstream scientific backing and we'll take it from there.
Aha, so now we see the truth coming out.... you are anti Mars missions/colonisation because you are a Musk-hater. Now it begins to make sense.
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Old 9th July 2018, 02:12 AM   #170
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Originally Posted by smartcooky View Post

Aha, so now we see the truth coming out.... you are anti Mars missions/colonisation because you are a Musk-hater. Now it begins to make sense.
I'm pretty sure he's not, but even if he were it wouldn't impact the validity of the arguments he's making.
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Old 9th July 2018, 04:25 AM   #171
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Originally Posted by Roboramma View Post
I'm pretty sure he's not, but even if he were it wouldn't impact the validity of the arguments he's making.
Nothing wrong with his arguments. He just presents them as insurmountable obstacles when they aren't. e.g.

Quote:
The kind of minor incoming rock that would burn up in Earth's atmosphere will punch a nice hole in it.
This is being presented in such a way as to imply its a show stopper. In fact a pressure dome is not going to explode if it gets a small puncture, neither is all the air going to zap out of it instantaneously. Even the ISS has a puncture repair kit to seal a hole if they get hit and holed by a meteor.

I also see radiation being presented as a show stopper. It isn't. An astronaut on the surface of Mars is subject to lower doses of radiation on a daily basis than an astronaut in the ISS. The long term health effects of radiation are a concern, so are the effects of air pollution on the Earth. The WHO estimates that 4.6 million people die each year from causes directly attributable to air pollution. That's more deaths per year than car accidents. One-third of ALL deaths in China are directly linked to air pollution.

The argument is made that dome habitats could just as easily be built on Earth as they could on Mars. While this is true, it is also true that domes on Mars are not susceptible to storms, hurricanes, earthquakes and volcanic activity because the latter three do not exist there and the atmospheric pressure means that the the most violent possible storm cannot do any damage.
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Old 9th July 2018, 04:42 AM   #172
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Originally Posted by phunk View Post
I didn't say anything about anthropogenic, I'm thinking longer term. The sun will get hotter with age, and the Earth will cook. We leave or we die.
When the Sun gets hotter Mars will cook as well. That's the essence of my argument in relation to Mars being a possible refuge from solar misbehaviour. Using Mars to escape from asteroid impact makes more sense, as I have argued.
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Old 9th July 2018, 05:33 AM   #173
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Originally Posted by smartcooky View Post
Aha, so now we see the truth coming out.... you are anti Mars missions/colonisation because you are a Musk-hater. Now it begins to make sense.

No. Pointing out that 'smart people' have proposed self-sustaining Mars colonies is no basis for stifling discussion, as you tried to do. Musk is a recent proponent of such a scheme so his name is an obvious one to choose.

I'm not anti-Mars exploration, nor an anti-Mars base. The self-sustaining Mars colony that will support human life indefinitely is what I'm arguing against.

But, hey, let's turn your argument around. Plenty of experienced space scientists pretty much laughed at Musk's plans. Do you think you're smarter than them in this area? See? It's a crap line of argument, isn't it? But not the first time you've employed it.
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Old 9th July 2018, 11:05 AM   #174
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Originally Posted by Roboramma View Post
If that window is tens, hundreds, or even maybe if it's thousands of years it suggests that we should get started now. If it's hundreds of millions of years I think we can afford to wait.

I accept that there is some validity to an argument based on those shorter time frames, but that argument should not be conflated with one based on longer timeframes.
Originally Posted by cjameshuff View Post
In short, an event that greatly limits the probability of us leaving Earth is little different from one that immediately renders us extinct, when it comes to long term survival. There's a variety of possible events that could do so in short timeframes.
Originally Posted by smartcooky View Post
If want to end up with established colonies on another planet WE NEED TO START LEARNING HOW TO DO IT NOW, as in between NOW and the next 50 years, the sooner the better, not in 100, 200 or 500 years time NOW, because the door is closing, and once it closes, we're done.

The big issue that doesn't seem to be getting through to the naysayers adequately is that of available resources. However vast they may seem now, resources on Earth are limited. Material resources are limited, and energy resources are limited. Even taking best-case with current nuclear technology, we're limited to a half-dozen centuries or so. Solar won't cover all humanity's energy needs, fusion might but it's been "a couple decades off" for substantially longer than I've been alive.

Waiting until we have to deal with runaway climate change is too late, period. Waiting until we have to deal with even most-likely-case current projections is still potentially making it un-tenably difficult.

Yes, it will be easier to survive on a changing Earth; but doing so will require more resources than we are currently spending. That means, obviously, that there will be fewer resources available to spend on space flight and colonization. With the rise of global temperatures, fewer zones will be habitable for long periods, and that combined with the increasing prevalence and strength of superstorms and other adverse weather conditions means that spaceflight will become more difficult and resource-intensive.

Eventually we'll pass a point where leaving this rock will be prohibitively difficult and expensive. So it's important to get started on it as soon as possible while we still have the resources and ability to do so.
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Old 9th July 2018, 12:40 PM   #175
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Originally Posted by Craig B View Post
When the Sun gets hotter Mars will cook as well. That's the essence of my argument in relation to Mars being a possible refuge from solar misbehaviour. Using Mars to escape from asteroid impact makes more sense, as I have argued.
Mars is significantly farther from the sun and doesn't have the atmosphere to retain heat like earth does. Mars won't get anywhere near as hot as Earth will. Also, the point of going to Mars isn't to live there forever. It's to learn to live there and develop the technology so we can continue to spread to other places.
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Old 9th July 2018, 03:36 PM   #176
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Originally Posted by GlennB View Post
Pressurised domes that let through light but cut out harmful radiation? The heat losses will be vast. The kind of minor incoming rock that would burn up in Earth's atmosphere will punch a nice hole in it. Will the metal-smelting and other heavy industries operate within the domes?

You're making this up as you go along, aren't you?
GlennB, many of the problems that you bring up are things anyone seriously thinking about Mars colonization has long ago thought of, and which take only a few moments of thought to come up with a variety of solutions for. You previously treated my suggestion of dropping a rover out the airlock to scout landing positions for subsequent craft and maybe do some light earthmoving as if it was some radical new approach that you would never have considered, when it's an obvious first approach to the problem.

To be blunt, you don't seem to be putting in the slightest bit of effort into coming up with possible solutions to the problems you come up with, or even doing any research to determine if they are actually all that severe. You simply assume they are insurmountable obstacles that Mars proponents have never thought of, and present them as such. When someone takes only a few moments to come up with a solution to some big problem you brought up, it doesn't mean they're just making things up as they go along, it means your supposed big problem isn't one.


In this particular case, for agriculture, the only radiation you need to shield against is UV. The pressure you need to contain is little more than the partial pressure of water vapor at the favored temperature of whatever plants you are growing. Your big insurmountable obstacle is something that could be done with a plastic bag.

Heat losses are not likely to be a major issue for the inhabited domes, they will likely produce net waste heat...which can be used as low grade heat for several industrial processes, such as ice sublimation or greenhouse warming. Greenhouses may need double walls or water loops, or other mechanisms to maintain their temperature. Low pressure inflatable surface greenhouses are likely entirely feasible, but it may turn out to be more effective to use indoor greenhouses with artificial lighting. There are many, many ways to approach this problem, and it's unlikely any one solution will be the best for all situations encountered in the real world. Lack of one clear best solution defined to the tiniest detail is not equivalent to lack of a solution.
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Old 9th July 2018, 04:29 PM   #177
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Originally Posted by cjameshuff View Post
To be blunt, you don't seem to be putting in the slightest bit of effort into coming up with possible solutions to the problems you come up with, or even doing any research to determine if they are actually all that severe. You simply assume they are insurmountable obstacles that Mars proponents have never thought of, and present them as such. When someone takes only a few moments to come up with a solution to some big problem you brought up, it doesn't mean they're just making things up as they go along, it means your supposed big problem isn't one.

It also means (in my case anyway) that this "someone" has already been over what GlennB brings up, i.e. nothing new to those of us who have been reading, thinking about and researching this topic for 30+ years.

My first book on prospective space colonisation was "The Greening of Mars" by James E. Lovelock CE CBE FRS and Michael Allaby which I bought in 1985 shortly after its release (Elon Musk was 13 so he didn't influence me to buy it!!)

This book sparked an interest in me that has never waned, and I still have it. My copy is a First Edition autographed by both authors.
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Old 9th July 2018, 05:13 PM   #178
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Originally Posted by smartcooky View Post
It also means (in my case anyway) that this "someone" has already been over what GlennB brings up, i.e. nothing new to those of us who have been reading, thinking about and researching this topic for 30+ years.

My first book on prospective space colonisation was "The Greening of Mars" by James E. Lovelock CE CBE FRS and Michael Allaby which I bought in 1985 shortly after its release (Elon Musk was 13 so he didn't influence me to buy it!!)

This book sparked an interest in me that has never waned, and I still have it. My copy is a First Edition autographed by both authors.
1985? You greenhorn, you!
https://en.wikipedia.org/wiki/The_Sands_of_Mars
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Old 9th July 2018, 05:45 PM   #179
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I think most of us are missing the point. We're going to do it because we want to. We'll find a way, because we think it'll be cool, and also some other reasons. There will be people who will say that it being cool isn't a good reason to do it, but they'll be ignored because some of the people who think it'll be cool also have a lot of money.
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Old 9th July 2018, 06:04 PM   #180
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Originally Posted by jonesdave116 View Post


I read the Sands of Mars when I was about 10 , and other even earlier material by such authors as George O. Smith, Stanley Weinbaum and H. Beam Piper (I loved "Omnilingual" for its treatment of science as a language that civilisations might have in common).

However, "The Greening of Mars" isn't sci-fi, its a reasonable attempt (given our level of knowledge at that time) to get to grips with what it would take to establish Mars as a place people could live, and is the first non-fiction book specifically about Mars that I read.
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Old 11th July 2018, 01:16 AM   #181
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Originally Posted by cjameshuff View Post
... In this particular case, for agriculture, the only radiation you need to shield against is UV.
Mars’ Surface Radiation Environment Measured with the Mars Science Laboratory’s Curiosity Rover:
Originally Posted by Hassler etal
There are two types of energetic particle radiation incident at the top of the Mars atmosphere, Galactic Cosmic Rays (GCRs) and Solar Energetic Particles (SEPs). Both GCRs and SEPs interact with the atmosphere and, if energetic enough, penetrate into the Martian soil, or regolith, where they produce secondary particles (including neutrons and γ-rays) that contribute to the complex radiation environment on the Martian surface, which is quite unlike that observed at the Earth’s surface.
Originally Posted by Hassler etal
... GCRs are difficult to shield against, and can penetrate up to several meters into the Martian regolith. SEPs are produced in the solar corona as a result of high energy processes associated with flares, coronal mass ejections (CMEs) and their corresponding shocks. SEP events are sporadic and difficult to predict, with onset times on the order of minutes to hours and durations of hours to days. SEP fluxes can vary by several orders of magnitude, and are typically dominated by protons, but composition can vary substantially.
...
However, during “hard spectrum” events, ions can be accelerated to energies well above 150 MeV/nuc with substantial fluxes reaching the Martian surface. In all events, secondary neutrons produced by SEPs in the atmosphere can reach the surface.
...
Originally Posted by cjameshuff
The pressure you need to contain is little more than the partial pressure of water vapor at the favored temperature of whatever plants you are growing. Your big insurmountable obstacle is something that could be done with a plastic bag.
I think something more than 'a plastic bag' might be needed to shield against the above variable intensity particle radiation fluxes:
The mechanical properties of most polymers are also very dependent on temperature. In fact, there aren't many that wouldn't enter the brittle 'glass' behavior region at even average Mars surface temperatures, and thus unaccounted for mechanical integrity, under anticipated design load conditions, becomes a significant factor of concern.

Note: I'm not saying any one of the above individual issues when considered in isolation, is necessarily a 'show-stopper', but the onus falls on the claimant to consider all operating conditions before asserting overall design feasibility, (or otherwise)

Citing technically incorrect 'facts', and then asserting designs and materials which, prima facie, would need to be called upon to operate outside of their optimal regions, does not inspire confidence in the presented arguments.
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Old 11th July 2018, 06:26 PM   #182
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Originally Posted by cjameshuff View Post
Greenhouses aren't going to experience deep subzero temperatures. Most of Mars doesn't experience temperatures as low as you claim, and greenhouses by their very function are constructed to minimize temperature swings, through insulation, thermal mass, and if necessary, through active heating. The thin atmosphere of Mars means that overheating is more likely to be the major issue. And again, the structural loads are so minuscule that even flimsy plastic is overkill.

Longer term DNA damage? Most of these plants live a few months, and then they get eaten. The vast majority won't even have the opportunity to reproduce, so that one growing season is all the radiation their DNA will ever be exposed to. For the seed plants for which this isn't true...if the radiation causes issues over multiple generations that can't be weeded out by selection, maintain a root strain grown indoors under the shielding used for the humans.
Yeah, this.
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Old 15th July 2018, 01:13 AM   #183
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Originally Posted by cjameshuff View Post
Your conclusion does not follow from your premise. Even if a Mars civilization wasn't likely to be mostly insensitive to climate, only climate shifts that simultaneously affected both Earth and Mars would threaten the existence of a civilization that has spread to both locations.



Relying on people surviving to "try again" is a poor substitute. Near-modern human populations have existed for millions of years. Behaviorally modern humanity has existed for ~50000 years. Humans eventually got around to building a complex technological civilization, but it's not inevitable. And doing it again, after all the most easily accessible deposits of ores and energy sources have been long exhausted, is far from a sure thing. And then there's the faulty assumption that the survivors will remember meaningful information about the events...


Only if your Mars colony is self sustainable.
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