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Zero-gravity (and by extension low-gravity) health effects are manageable, but: for months (so far), and by military-grade athletes with the self-discipline to

Zero-gravity (and by extension low-gravity) health effects are manageable, but: for months (so far), and by military-grade athletes with the self-discipline to exercise every single day. This is quite different from: a whole population, and for many decades. The long-term health effects of low gravity are not a solved issue as far as I know: https://www.scientificamerican.com/article/how-does-spending-prolong/ https://www.scientificamerican.com/article/how-does-spending... https://www.wired.com/2014/02/happens-body-mars/ https://www.wired.com/2014/02/happens-body-mars/ I asked about gravity and not the (many) other issues because we have at least some hints on how to handle say radiation shielding, however we have no idea how to change gravity if it does indeed prove to be a blocking point for permanent settlements.

jessriedel 9y ago
First, I don't think the extension of ill-effects to low-gravity is obvious at all. (I.e., no reason to expect this is linear. The benefits of exercise on Earth have greatly diminishing returns, and I expect the same for gravity exposure.) Second, I don't see why we expect ill-effects to go from manageable to unmanageable with normal people. Astronauts on MIR weren't dropping dead before the started the rigorous exercise programs. By all means, file this under "possible, as-yet unquantified risk". It's certainly conceivable that there is some killer disease the crops up in 1/3 gravity if you don't exercise daily. But right now I don't think we have any data that's inconsistent with the reasonable first guess that normal people will be basically fine in 1/3 gravity. (This maybe just a question of what we mean by "basically". To me, a 10% lowering of life-expectancy is acceptable and expected when colonizing another planet. The trip itself will probably be a few percent chance of death.) On the other hand, we have fairly large, well-quantified risks for radiation exposure of long-term living on Mars, and we have no obvious way to solve it without huge concrete structures, underground tunneling, or as-yet-uninvented magnetic shields. EDIT: Actually, I retract my claim that this is a bigger worry than low gravity as I am no longer sure. The radiation exposure is less than I thought, and likely reduces life expectancy by less than 5%. https://www.nasa.gov/sites/default/files/files/1_NAC_HEO_SMD_Committee_Mars_Radiation_Intro_2015April7_Final_TAGGED.pdf https://www.nasa.gov/sites/default/files/files/1_NAC_HEO_SMD... http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0074988 http://journals.plos.org/plosone/article?id=10.1371/journal.... http://www.space.com/18753-mars-radiation-manned-mission.html http://www.space.com/18753-mars-radiation-manned-mission.htm...

jessriedel 9y ago

First, I don't think the extension of ill-effects to low-gravity is obvious at all. (I.e., no reason to expect this is linear. The benefits of exercise on Earth have greatly diminishing returns, and I expect the same for gravity exposure.) Second, I don't see why we expect ill-effects to go from manageable to unmanageable with normal people. Astronauts on MIR weren't dropping dead before the started the rigorous exercise programs. By all means, file this under "possible, as-yet unquantified risk". It's certainly conceivable that there is some killer disease the crops up in 1/3 gravity if you don't exercise daily. But right now I don't think we have any data that's inconsistent with the reasonable first guess that normal people will be basically fine in 1/3 gravity. (This maybe just a question of what we mean by "basically". To me, a 10% lowering of life-expectancy is acceptable and expected when colonizing another planet. The trip itself will probably be a few percent chance of death.) On the other hand, we have fairly large, well-quantified risks for radiation exposure of long-term living on Mars, and we have no obvious way to solve it without huge concrete structures, underground tunneling, or as-yet-uninvented magnetic shields. EDIT: Actually, I retract my claim that this is a bigger worry than low gravity as I am no longer sure. The radiation exposure is less than I thought, and likely reduces life expectancy by less than 5%. https://www.nasa.gov/sites/default/files/files/1_NAC_HEO_SMD_Committee_Mars_Radiation_Intro_2015April7_Final_TAGGED.pdf https://www.nasa.gov/sites/default/files/files/1_NAC_HEO_SMD... http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0074988 http://journals.plos.org/plosone/article?id=10.1371/journal.... http://www.space.com/18753-mars-radiation-manned-mission.html http://www.space.com/18753-mars-radiation-manned-mission.htm...