Okay, first there are a few places in the solar system where there is an economic point for Earth.
For instance the Martian moon Deimos could supply ice to LEO. Robert Walker's answer to Are the moons of Mars, Phobos and Deimos, also suitable for off-world colonization?
Though I haven't seen any economic justification for Earth of colonizing the Mars surface in near future - no resource currently known on Mars is worth the cost of returning it to Earth or LEO.
To colonize anywhere outside of Earth we need something that makes it a better place to be than Earth. Otherwise why not just build domed cities on the deserts here? Surely orders of magnitudes easier.
Or build salt water greenhouses in the deserts. Again costs far far less per colonist, easier to maintain, far easier to be self sufficient if that's your aim.
Responsibly growing with seawater and sunlight
I think - you may be surprised until you work through the details - but - expressing a personal point of view here - I think quite probably easier to build than a Mars colony or anywhere else in space - especially - easier to scale up to a large scale working low maintenance colony.
But still - many issues involved - and - far harder to build than a comparable colony on the Earth. And main problem with a Venus colony as with a Mars colony is - what's the point - why are you there?
For more on this, see Robert Walker's answer to Where should Earth's 1st off-planet colony start?
So - could be mining for resources to return to Earth or LEO. Also could be creating solar satellites. Both directly benefit Earth.
But in near future I see space exploration and discovery as the primary motivation.
Spaceguard is already well underway and NASA have been tasked with finding 90% of all potential impactors of 140 meters or less by 2020. Chance that there will be an undetected 10 km diameter disaster will be minute, and not likely that they will find one either - most likely that this won't happen for several hundred thousand generations into the future.
And even that is far smaller than the asteroid needed to make Earth so inhabitable that we would need to escape Earth to avoid it. That would need to be more like a small moon in size. And other potential disasters such as gamma bursts would leave many human survivors on Earth, in best place to rebuild civilization in our solar system. Whatever species we or other creatures on Earth evolve into 500 million years from now or a billion years from now when our seas boil dry and a (rather tiny) chance of resonances with Jupiter destabilizing inner solar system with Mercury hitting Earth - they may well need to leave Earth to avoid extinction.
But it is not urgent to do that now, on the geological timescale, and we can't anticipate and plan for something that will not happen for 500 million years. E.g. if we were to terraform Mars - then the planet would only remain terraformed on timescales of perhaps hundreds of thousands or millions of years - due to lack of continental drift (to return limestone to atmosphere as CO2), lack of magnetic field (to protection water vapour in its atmosphere from solar dissociation) and it's position so much further from the sun (probably requiring continuous mega-engineering such as giant mirrors or greenhouse gases or both to keep it warm). At some point it would unterraform - possibly as quickly as it was terraformed, and we surely can't guarantee that our technology will persist for half a billion years or longer.
For Mars - that has potential for great drive towards exploration if we discover life there that is different from Earth life - past or present - which I think myself is very likely. It may surprise you - but we haven't even started on a proper exobiological exploration of Mars - with ExoMars in 2018 due to be the first rover since Viking to have capabilities to detect biosignatures on Mars in the low concentrations expected on a planet that is basically in a permanent "snowball" phase - but with less ice than the Earth had in its past snowball phases.
It's searching for past life - searching for present day life is in some ways more challenging (harder locations to get to, and needs better sterilization) and would be for future rovers.
The best way to explore it, if searching for life, is by telerobotics - because you have the ability to explore sensitive areas without any risk of contaminating the surface with Earth life, and with all the benefits of human "on the spot" decision making, without the dangers and encumberances of spacesuits and surface landing.
It's reasonably uncontroversial that sending humans to the surface of Mars at least greatly increases risk of contaminating it with Earth life - especially when you take account of the possibility of a hard landing - and none of the technologies being explored can give you a reasonable probability of successs. For a guideline - then for robotic missions, they work on the basis of less than a 1 in 10,000 chance per mission of contaminating the destination object (though for Mars they don't do a probability calculation any more because there are too many unknowns to do it reliably).
With a hard landing of humans surely amounting to a near 100% chance of contaminating Mars (through dormant micro-organisms spread over the surface of Mars in the dust storms), then hard to see how that alone could be brought to less than that 1 in 10,000 chance per mission of contamination never mind what happens after they land on Mars (not feasible to land a biohazard containment facility with human microbes as the biohazard to contain and many issues with spacesuit leaking, venting wastes from habitats, etc).
So surely humans greatly increase chance of contamination of the surface.
And in near future much of exploration I think will be telerobotics anyway. Apart from anything else -who wants to risk losing ten years of your life to cancer, even if the risk is only a few percent - by spending a lot of time out of doors in spacesuits?
People worry about skin cancer due to sun bathing on the Earth and take steps to prevent it. For sure when we have space settlements they will be greatly concerned about spending too much time in spacesuits and rovers outside their habitats. Young children and babies probably never allowed outside at all.
So - though back in say 2008, the plans for colonizing Mars seemed quite feasible from a planetary protection point of view - is hard to see how they can be shown to be okay now -especially with recent discoveries of the warm seasonal flows. Robert Zubrin's argument that Mars life is already the same as Earth life in all respects would be a major and surprising discovery in it's own right if it turned out to be true, and can't be used as a basis for planetary protection policy decisions without conclusive proof. Many reasons for expecting Mars life to be considerably different from Earth life.
I know that you still get articles suggesting human biological exploration of the surface of Mars. But these generally don't even address the contamination issues. Until they do, I don't think they can be considered to be a complete and full foreshadowing of the future.
I hope myself that much of the work done by Mars society etc on exploring Mars with humans on the surface can be adapted - almost unchanged - for telerobotic exploration with telerobotic avatars on the surface. Even ideas for creating fuel on the Mars surface - those would be very useful for telerobotic exploration. And ideas for growing plants - well those also can be adapted for telerobotics, exporting food to Mars orbit from the surface - as large plants such as tomatoes, trees etc can be grown hydroponically without need to have any microbes at all - so no risk of contaminating Mars.
And - even Robert Zubrin - he suggested precursor telerobotic missions to Mars with his double Athena flyby.
So - perhaps - by delaying landing on Mars long enough to explore it thoroughly from orbit - we can walk together for the next few decades - both those who think it is safe to colonize Mars and those who think it needs to be kept pristine f0r the future benefit to humanity of discoveries we are likely to make about Mars biochemistry - until we know enough to make a truly informed decision about what to do.
Also could be of economic benefit to Earth - mining the moons of Mars for fuel for LEO - if we decide that's okay to do. At any rate far easier to show acceptable for planetary protection than landing humans on Mars.
(Though it would still take a great deal of care to send humans to low Mars orbit and to Deimos or Phobos with no significant chance of crashing onto the surface of the planet. Aerobraking for instance would probably not be safe enough to get that less than 1 in 10,000 chance of a crash - in early stages I think a close to Mars capture orbit - the HERRO style slowly sun precessing 12 hour Molniya orbit - or the free return double Athena flyby is safest for planetary protection).
And after all - if the Mars colonization enthusiasts are right and it does turn out to be okay to colonize the surface for one reason or another - well all of this is building up infra-structure and knowledge that will help in the future including thorough in depth survey, numerous robots on the surface of Mars, and fuel generation plants etc etc. And orbital settlements around Mars and easy transfer from Mars orbit to / from Earth - all that is surely a big plus if we did ever decide to colonize the surface.
And work on terraforming Mars - that's of great interest for understanding other planets especially exoplanets - and the Earth - is great to work on the ideas. But practically - that's not something, in my view - that we should do any time soon. Because we know too little about possible consequences - and takes so long, mega-engineering for a thousand years and that's just the start - and so many things to go wrong.
That's also another reason for delaying human landing on Mars - because that amounts to a totally unplanned introduction of tens of thousands of species of Earth life to Mars - with by far the majority of them not yet studied or characterized, and only known from DNA fragments (the Microbial dark matter).
Terraforming Mars - if possible at all - may well work better with a step by step introduction, e.g. to start with just cyanobacteria, say, quite probably for a few centuries before you introduce aerobes.
Never mind all the various microbes that live in and on human bodies and in our habitats - in the air and our crops - in an unplanned release of whatever is inside human habitats to the surface of Mars (in a crash landing say) - who knows what they would evolve into on Mars, the few that survive in the UV and cosmic radiation - or what they would do to humans or our crops or the air we breath when they return to the habitats, or how they would transform Mars as they replicate in the various potential Mars habitats.
(That includes some Earth microbes possibly able to survive as primary producer single species ecosystems just using night time humidity almost anywhere on surface of Mars (probably depending on nitrogen availability but Curiosity has found nitrates on Mars) and photosythesize in the Martian sunlight, from the DLR experiments and at least a chance of widespread deliquescing salt habitats on Mars also, damp patches, a few mm thick, just a cm or so below the soil surface - any new present day planetary protection assessment would have to look into these and various other possibilities for Earth life to survive on present day Mars in detail).
See also
For instance the Martian moon Deimos could supply ice to LEO. Robert Walker's answer to Are the moons of Mars, Phobos and Deimos, also suitable for off-world colonization?
Though I haven't seen any economic justification for Earth of colonizing the Mars surface in near future - no resource currently known on Mars is worth the cost of returning it to Earth or LEO.
To colonize anywhere outside of Earth we need something that makes it a better place to be than Earth. Otherwise why not just build domed cities on the deserts here? Surely orders of magnitudes easier.
Or build salt water greenhouses in the deserts. Again costs far far less per colonist, easier to maintain, far easier to be self sufficient if that's your aim.
Responsibly growing with seawater and sunlight
Far easier to do this than to build colonies in space - and create livelihoods and food for far more people for same cost.From an engineering point of view, then if you are set on going into space - then Venus cloud colonies may be the easiest to build - certainly least mass per colonist - and no need for radiation shielding
Why are we thinking about a Mars colony when a Venus colony would be more technically feasible? It seems that radiation shielded floating colonies could be assembled on Venus, with plastic film and aluminum wire bags, filled with breathable air.
I think - you may be surprised until you work through the details - but - expressing a personal point of view here - I think quite probably easier to build than a Mars colony or anywhere else in space - especially - easier to scale up to a large scale working low maintenance colony.
But still - many issues involved - and - far harder to build than a comparable colony on the Earth. And main problem with a Venus colony as with a Mars colony is - what's the point - why are you there?
For more on this, see Robert Walker's answer to Where should Earth's 1st off-planet colony start?
So - could be mining for resources to return to Earth or LEO. Also could be creating solar satellites. Both directly benefit Earth.
But in near future I see space exploration and discovery as the primary motivation.
NOT NEEDED FOR ESCAPE FROM ASTEROID IMPACTS OR OTHER NATURAL DISASTERS
Spaceguard is already well underway and NASA have been tasked with finding 90% of all potential impactors of 140 meters or less by 2020. Chance that there will be an undetected 10 km diameter disaster will be minute, and not likely that they will find one either - most likely that this won't happen for several hundred thousand generations into the future.
And even that is far smaller than the asteroid needed to make Earth so inhabitable that we would need to escape Earth to avoid it. That would need to be more like a small moon in size. And other potential disasters such as gamma bursts would leave many human survivors on Earth, in best place to rebuild civilization in our solar system. Whatever species we or other creatures on Earth evolve into 500 million years from now or a billion years from now when our seas boil dry and a (rather tiny) chance of resonances with Jupiter destabilizing inner solar system with Mercury hitting Earth - they may well need to leave Earth to avoid extinction.
But it is not urgent to do that now, on the geological timescale, and we can't anticipate and plan for something that will not happen for 500 million years. E.g. if we were to terraform Mars - then the planet would only remain terraformed on timescales of perhaps hundreds of thousands or millions of years - due to lack of continental drift (to return limestone to atmosphere as CO2), lack of magnetic field (to protection water vapour in its atmosphere from solar dissociation) and it's position so much further from the sun (probably requiring continuous mega-engineering such as giant mirrors or greenhouse gases or both to keep it warm). At some point it would unterraform - possibly as quickly as it was terraformed, and we surely can't guarantee that our technology will persist for half a billion years or longer.
SEARCH FOR LIFE AS POTENTIALLY MAIN REASON FOR EXPLORING SPACE
For Mars - that has potential for great drive towards exploration if we discover life there that is different from Earth life - past or present - which I think myself is very likely. It may surprise you - but we haven't even started on a proper exobiological exploration of Mars - with ExoMars in 2018 due to be the first rover since Viking to have capabilities to detect biosignatures on Mars in the low concentrations expected on a planet that is basically in a permanent "snowball" phase - but with less ice than the Earth had in its past snowball phases.
It's searching for past life - searching for present day life is in some ways more challenging (harder locations to get to, and needs better sterilization) and would be for future rovers.
The best way to explore it, if searching for life, is by telerobotics - because you have the ability to explore sensitive areas without any risk of contaminating the surface with Earth life, and with all the benefits of human "on the spot" decision making, without the dangers and encumberances of spacesuits and surface landing.
HUMAN HARD LANDING PROTECTION ISSUES
It's reasonably uncontroversial that sending humans to the surface of Mars at least greatly increases risk of contaminating it with Earth life - especially when you take account of the possibility of a hard landing - and none of the technologies being explored can give you a reasonable probability of successs. For a guideline - then for robotic missions, they work on the basis of less than a 1 in 10,000 chance per mission of contaminating the destination object (though for Mars they don't do a probability calculation any more because there are too many unknowns to do it reliably).
With a hard landing of humans surely amounting to a near 100% chance of contaminating Mars (through dormant micro-organisms spread over the surface of Mars in the dust storms), then hard to see how that alone could be brought to less than that 1 in 10,000 chance per mission of contamination never mind what happens after they land on Mars (not feasible to land a biohazard containment facility with human microbes as the biohazard to contain and many issues with spacesuit leaking, venting wastes from habitats, etc).
So surely humans greatly increase chance of contamination of the surface.
FUTURE OF SPACE EXPLORATION GENERALLY - TELEROBOTICS
And in near future much of exploration I think will be telerobotics anyway. Apart from anything else -who wants to risk losing ten years of your life to cancer, even if the risk is only a few percent - by spending a lot of time out of doors in spacesuits?
People worry about skin cancer due to sun bathing on the Earth and take steps to prevent it. For sure when we have space settlements they will be greatly concerned about spending too much time in spacesuits and rovers outside their habitats. Young children and babies probably never allowed outside at all.
HARD TO SEE HOW THE 2008 AND EARLIER PLANS FOR COLONIZING MARS COULD BE SHOWN TO BE OKAY NOW FOR PLANETARY PROTECTION
So - though back in say 2008, the plans for colonizing Mars seemed quite feasible from a planetary protection point of view - is hard to see how they can be shown to be okay now -especially with recent discoveries of the warm seasonal flows. Robert Zubrin's argument that Mars life is already the same as Earth life in all respects would be a major and surprising discovery in it's own right if it turned out to be true, and can't be used as a basis for planetary protection policy decisions without conclusive proof. Many reasons for expecting Mars life to be considerably different from Earth life.
I know that you still get articles suggesting human biological exploration of the surface of Mars. But these generally don't even address the contamination issues. Until they do, I don't think they can be considered to be a complete and full foreshadowing of the future.
ADAPTATION TO TELEROBOTICS
I hope myself that much of the work done by Mars society etc on exploring Mars with humans on the surface can be adapted - almost unchanged - for telerobotic exploration with telerobotic avatars on the surface. Even ideas for creating fuel on the Mars surface - those would be very useful for telerobotic exploration. And ideas for growing plants - well those also can be adapted for telerobotics, exporting food to Mars orbit from the surface - as large plants such as tomatoes, trees etc can be grown hydroponically without need to have any microbes at all - so no risk of contaminating Mars.
And - even Robert Zubrin - he suggested precursor telerobotic missions to Mars with his double Athena flyby.
IF WE DELAY HUMAN LANDING AND EXPLORE TELEROBOTICALLY - CAN WALK TOGETHER WITHOUT CONTROVERSY UNTIL WE KNOW MORE
So - perhaps - by delaying landing on Mars long enough to explore it thoroughly from orbit - we can walk together for the next few decades - both those who think it is safe to colonize Mars and those who think it needs to be kept pristine f0r the future benefit to humanity of discoveries we are likely to make about Mars biochemistry - until we know enough to make a truly informed decision about what to do.
Also could be of economic benefit to Earth - mining the moons of Mars for fuel for LEO - if we decide that's okay to do. At any rate far easier to show acceptable for planetary protection than landing humans on Mars.
(Though it would still take a great deal of care to send humans to low Mars orbit and to Deimos or Phobos with no significant chance of crashing onto the surface of the planet. Aerobraking for instance would probably not be safe enough to get that less than 1 in 10,000 chance of a crash - in early stages I think a close to Mars capture orbit - the HERRO style slowly sun precessing 12 hour Molniya orbit - or the free return double Athena flyby is safest for planetary protection).
And after all - if the Mars colonization enthusiasts are right and it does turn out to be okay to colonize the surface for one reason or another - well all of this is building up infra-structure and knowledge that will help in the future including thorough in depth survey, numerous robots on the surface of Mars, and fuel generation plants etc etc. And orbital settlements around Mars and easy transfer from Mars orbit to / from Earth - all that is surely a big plus if we did ever decide to colonize the surface.
TROUBLE WITH TERRAFORMING MARS
And work on terraforming Mars - that's of great interest for understanding other planets especially exoplanets - and the Earth - is great to work on the ideas. But practically - that's not something, in my view - that we should do any time soon. Because we know too little about possible consequences - and takes so long, mega-engineering for a thousand years and that's just the start - and so many things to go wrong.
That's also another reason for delaying human landing on Mars - because that amounts to a totally unplanned introduction of tens of thousands of species of Earth life to Mars - with by far the majority of them not yet studied or characterized, and only known from DNA fragments (the Microbial dark matter).
Terraforming Mars - if possible at all - may well work better with a step by step introduction, e.g. to start with just cyanobacteria, say, quite probably for a few centuries before you introduce aerobes.
Never mind all the various microbes that live in and on human bodies and in our habitats - in the air and our crops - in an unplanned release of whatever is inside human habitats to the surface of Mars (in a crash landing say) - who knows what they would evolve into on Mars, the few that survive in the UV and cosmic radiation - or what they would do to humans or our crops or the air we breath when they return to the habitats, or how they would transform Mars as they replicate in the various potential Mars habitats.
(That includes some Earth microbes possibly able to survive as primary producer single species ecosystems just using night time humidity almost anywhere on surface of Mars (probably depending on nitrogen availability but Curiosity has found nitrates on Mars) and photosythesize in the Martian sunlight, from the DLR experiments and at least a chance of widespread deliquescing salt habitats on Mars also, damp patches, a few mm thick, just a cm or so below the soil surface - any new present day planetary protection assessment would have to look into these and various other possibilities for Earth life to survive on present day Mars in detail).
See also
About the Author
Robert Walker
Writer of articles on Mars and Space issues - Software Developer of Tune Smithy, Bounce Metronome etc.Studied at Wolfson College, Oxford
Lives in Isle of Mull
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