4 ms·

The Moon has very little hydrogen, carbon and nitrogen, which Mars has in abundance. These are very important elements both for biology and chemistry. E.g. if y

by bbojan 5y ago

The Moon has very little hydrogen, carbon and nitrogen, which Mars has in abundance. These are very important elements both for biology and chemistry. E.g. if you want to have a self-sufficient colony outside Earth, you could do it on Mars but not on the Moon. Mars could be terraformed (in theory); the Moon never could.

revicon 5y ago
With no magnetosphere would there even be a point to terraforming?
- ceejayoz 5y ago
  Terraforming is an engineering project on such a scale it's probably reasonable to assume advancements like radiation resistance/repair in humans and artificial magnetic fields. For example, this apparently feasible (but currently batshit crazy) proposal: https://www.universetoday.com/153368/an-absolutely-bonkers-plan-to-give-mars-an-artificial-magnetosphere/ https://www.universetoday.com/153368/an-absolutely-bonkers-p...
- bryanlarsen 5y ago
  Maintaining an atmosphere is a lot easier than creating it in the first place, and can use the same process and machines. In other words just live with the slow loss and replace the loss gradually.
  - revicon 5y ago
    I think what I meant is with no magnetosphere we would all die of radiation exposure regardless if there was a terraformed atmosphere or not. Without a magnetosphere we'd all be living underground anyway, no point in terraforming.
- nine_k 5y ago
  A strategically placed powerful magnet outside Mars can protect from the solar wind. There is an orbit that places the orbiting body always on the line between Mars and Sun. Place a superconducting magnet there that generates a few Tesla. Due to the distance from the planet, even though the magnet will deflect more distant particles to relatively small angles, this should still be enough to keep Mars completely in the "shadow". Of course you'll have to and solar-powered thrusters to keep it on the orbit, and fly regular missions to replenish fuel in the ion drives. But thil looks doable even with today's level of technology, given enough money.
  - potiuper 5y ago
    The ‘intuitive’ strategy of building a compact electromagnet and placing it between Mars and the Sun at the first Lagrange point is unfeasible. The most feasible design is to encircle or wrap Mars at the equator with a superconducting wire loop. The resulting wire diameter could be as small as ∼5 cm. With this design, the magnetic shield would have a mass of ∼10^12 g and would require mining ∼10^18 g, or only 0.1% of Olympus Mons. https://arxiv.org/pdf/2006.05546.pdf https://arxiv.org/pdf/2006.05546.pdf
jmyeet 5y ago
> The Moon has very little hydrogen, That's not quite true. The Moon definitely has polar ice but it also likely has more water than that [1][2]. Nitrogen seems only to be present in trace quantities [3]. > Mars could be terraformed (in theory); the Moon never could. Yes and no (on both). People who make this claim often don't understand the magnitude of what they're claiming. Here's just one perspective: molecular velocities in the atmosphere are (of course) a Boltzmann distribution. As such a small percentage of those particles achieve escape velocity and fly off into space (called the Jeans escape energy) in exactly the same way that liquid water cools by evaporation. That amounts to around one million tonnes per year. Mars has a lower gravity so the loss would be greater at Earth atmospheric pressure and that's just the loss you need to account for and gas that you need to manufacture or produce. Earth's atmosphere has a mass of ~5x10^18 kg. The scale of producing this just in terms of energy consumption is insanely massive. So when you're talking about this level of energy expenditure it doesn't really matter all that much if you do it on the Moon or Mars. But what's more, terraforming would necessarily be extremely violent. Do it too fast and you cook the planet. The likely way of getting what you need there is by impacting large bodies from space into the Moon. You probably don't want to live there while doing that. The timescales are likely to be in the thousands of years. [1]: https://www.nasa.gov/press-release/nasa-s-sofia-discovers-water-on-sunlit-surface-of-moon https://www.nasa.gov/press-release/nasa-s-sofia-discovers-wa... [2]: https://www.planetary.org/articles/water-on-the-moon-guide https://www.planetary.org/articles/water-on-the-moon-guide [3]: https://en.wikipedia.org/wiki/Geology_of_the_Moon#Elemental_composition https://en.wikipedia.org/wiki/Geology_of_the_Moon#Elemental_...

by bbojan 5y ago

revicon 5y ago

With no magnetosphere would there even be a point to terraforming?

ceejayoz 5y ago
Terraforming is an engineering project on such a scale it's probably reasonable to assume advancements like radiation resistance/repair in humans and artificial magnetic fields. For example, this apparently feasible (but currently batshit crazy) proposal: https://www.universetoday.com/153368/an-absolutely-bonkers-plan-to-give-mars-an-artificial-magnetosphere/ https://www.universetoday.com/153368/an-absolutely-bonkers-p...
bryanlarsen 5y ago
Maintaining an atmosphere is a lot easier than creating it in the first place, and can use the same process and machines. In other words just live with the slow loss and replace the loss gradually.
- revicon 5y ago
  I think what I meant is with no magnetosphere we would all die of radiation exposure regardless if there was a terraformed atmosphere or not. Without a magnetosphere we'd all be living underground anyway, no point in terraforming.
nine_k 5y ago
A strategically placed powerful magnet outside Mars can protect from the solar wind. There is an orbit that places the orbiting body always on the line between Mars and Sun. Place a superconducting magnet there that generates a few Tesla. Due to the distance from the planet, even though the magnet will deflect more distant particles to relatively small angles, this should still be enough to keep Mars completely in the "shadow". Of course you'll have to and solar-powered thrusters to keep it on the orbit, and fly regular missions to replenish fuel in the ion drives. But thil looks doable even with today's level of technology, given enough money.
- potiuper 5y ago
  The ‘intuitive’ strategy of building a compact electromagnet and placing it between Mars and the Sun at the first Lagrange point is unfeasible. The most feasible design is to encircle or wrap Mars at the equator with a superconducting wire loop. The resulting wire diameter could be as small as ∼5 cm. With this design, the magnetic shield would have a mass of ∼10^12 g and would require mining ∼10^18 g, or only 0.1% of Olympus Mons. https://arxiv.org/pdf/2006.05546.pdf https://arxiv.org/pdf/2006.05546.pdf

jmyeet 5y ago

> The Moon has very little hydrogen, That's not quite true. The Moon definitely has polar ice but it also likely has more water than that [1][2]. Nitrogen seems only to be present in trace quantities [3]. > Mars could be terraformed (in theory); the Moon never could. Yes and no (on both). People who make this claim often don't understand the magnitude of what they're claiming. Here's just one perspective: molecular velocities in the atmosphere are (of course) a Boltzmann distribution. As such a small percentage of those particles achieve escape velocity and fly off into space (called the Jeans escape energy) in exactly the same way that liquid water cools by evaporation. That amounts to around one million tonnes per year. Mars has a lower gravity so the loss would be greater at Earth atmospheric pressure and that's just the loss you need to account for and gas that you need to manufacture or produce. Earth's atmosphere has a mass of ~5x10^18 kg. The scale of producing this just in terms of energy consumption is insanely massive. So when you're talking about this level of energy expenditure it doesn't really matter all that much if you do it on the Moon or Mars. But what's more, terraforming would necessarily be extremely violent. Do it too fast and you cook the planet. The likely way of getting what you need there is by impacting large bodies from space into the Moon. You probably don't want to live there while doing that. The timescales are likely to be in the thousands of years. [1]: https://www.nasa.gov/press-release/nasa-s-sofia-discovers-water-on-sunlit-surface-of-moon https://www.nasa.gov/press-release/nasa-s-sofia-discovers-wa... [2]: https://www.planetary.org/articles/water-on-the-moon-guide https://www.planetary.org/articles/water-on-the-moon-guide [3]: https://en.wikipedia.org/wiki/Geology_of_the_Moon#Elemental_composition https://en.wikipedia.org/wiki/Geology_of_the_Moon#Elemental_...