I suppose the main counterargument would be that we only need the Mars colony for the case of Earth getting hit by an asteroid and losing all large mammals, including humans. The Marsians would then somehow survive without supplies coming from Earth, wait until the situation on Earth has normalized, and then use a spacecraft with some fuel left to colonize Earth again. Humanity maybe saved.
By now you probably can tell I'm making my rounds through Wood From Eden; this is a wonderful blog, and I hope my comments will stimulate further readers to participate. The reason I took so long to get around to reading this particular essay was because I agreed with it beforehand. Mars is a terrible destination for colonization and will be for the foreseeable future, and everything you say is (or jolly well should be) well known among physicists, even if the general public doesn't really understand it. The only comments I can make are quibbles or asides, but here they are:
Weak sunlight is a very minor issue. Nuclear power is already most efficient for providing electricity even on Earth, and its potential for improvement is far better than solar power - I think we can reasonably expect fusion reactors within the next hundred years.
Weak gravity, by contrast, is an absolutely enormous issue.
Firstly, planets with gravity significantly weaker than that on Earth cannot retain water in their atmosphere: https://en.wikipedia.org/wiki/Atmospheric_escape . This means that Terraforming, and sustainable surface agriculture, will never be possible on Mars. Life will be confined to biospheres. Do note that the glass on these biospheres would turn them into greenhouses, raising temperatures to useful levels. And, since the limiting factor of plant growth on Earth is (surprisingly!) not sunlight, but rather warmth, crops could reasonably be expected to thrive on Martian Biospheres, growing to extreme heights in the low gravity. Speaking optimistically, there could be a market for enormous Mars-grown produce, though the shipping costs of course would be astronomical.
Secondly, humans do not thrive in low gravity environments. Although any level of gravity can be simulated in space stations by rotation, it would be highly expensive and likely quite dangerous to create a rotating station on Mars to amplify the weak Martian gravity. More likely people would wear weights and make use of magnetized footwear to improve maneuverability and stave off emaciation, but it's hard to imagine that most people would want to move to Mars knowing that over time their bodies would grow flabby, unappealing, and too weak to return to Earth. Again, speaking optimistically, it might be appealing to the bedridden, wheelchair-bound, and morbidly obese; but when people came to associate Martian living with the rich and physically disabled, the mystique of faraway living beneath Phobos and Deimos would quickly sour.
Lastly, there are alternative environments much closer to home which do not lack these disadvantages. Life in polar biodomes, or in aquatic bubbles, would be much cheaper (no need to escape Earth's gravity well) and safer (help is never more than 20,000 km away). Submarine living in particular could be attractive, as the water would maintain moderate internal temperature, offer access to fish from outside the bubble, and even allow for mobility - imagine a submarine colony that followed currents to different oceans at different depths throughout the year, allowing people to enter or leave an aquatic city from countries all across the dry land surface of the Earth. Mars cannot compete with that.
I suppose the main counterargument would be that we only need the Mars colony for the case of Earth getting hit by an asteroid and losing all large mammals, including humans. The Marsians would then somehow survive without supplies coming from Earth, wait until the situation on Earth has normalized, and then use a spacecraft with some fuel left to colonize Earth again. Humanity maybe saved.
By now you probably can tell I'm making my rounds through Wood From Eden; this is a wonderful blog, and I hope my comments will stimulate further readers to participate. The reason I took so long to get around to reading this particular essay was because I agreed with it beforehand. Mars is a terrible destination for colonization and will be for the foreseeable future, and everything you say is (or jolly well should be) well known among physicists, even if the general public doesn't really understand it. The only comments I can make are quibbles or asides, but here they are:
Weak sunlight is a very minor issue. Nuclear power is already most efficient for providing electricity even on Earth, and its potential for improvement is far better than solar power - I think we can reasonably expect fusion reactors within the next hundred years.
Weak gravity, by contrast, is an absolutely enormous issue.
Firstly, planets with gravity significantly weaker than that on Earth cannot retain water in their atmosphere: https://en.wikipedia.org/wiki/Atmospheric_escape . This means that Terraforming, and sustainable surface agriculture, will never be possible on Mars. Life will be confined to biospheres. Do note that the glass on these biospheres would turn them into greenhouses, raising temperatures to useful levels. And, since the limiting factor of plant growth on Earth is (surprisingly!) not sunlight, but rather warmth, crops could reasonably be expected to thrive on Martian Biospheres, growing to extreme heights in the low gravity. Speaking optimistically, there could be a market for enormous Mars-grown produce, though the shipping costs of course would be astronomical.
Secondly, humans do not thrive in low gravity environments. Although any level of gravity can be simulated in space stations by rotation, it would be highly expensive and likely quite dangerous to create a rotating station on Mars to amplify the weak Martian gravity. More likely people would wear weights and make use of magnetized footwear to improve maneuverability and stave off emaciation, but it's hard to imagine that most people would want to move to Mars knowing that over time their bodies would grow flabby, unappealing, and too weak to return to Earth. Again, speaking optimistically, it might be appealing to the bedridden, wheelchair-bound, and morbidly obese; but when people came to associate Martian living with the rich and physically disabled, the mystique of faraway living beneath Phobos and Deimos would quickly sour.
Lastly, there are alternative environments much closer to home which do not lack these disadvantages. Life in polar biodomes, or in aquatic bubbles, would be much cheaper (no need to escape Earth's gravity well) and safer (help is never more than 20,000 km away). Submarine living in particular could be attractive, as the water would maintain moderate internal temperature, offer access to fish from outside the bubble, and even allow for mobility - imagine a submarine colony that followed currents to different oceans at different depths throughout the year, allowing people to enter or leave an aquatic city from countries all across the dry land surface of the Earth. Mars cannot compete with that.