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The moon's core isn't made of the swirling molten iron dynamo like Earth's is. No swirling molten iron, no magnetic field. No magnetic field, nothing deflects t

The moon's core isn't made of the swirling molten iron dynamo like Earth's is. No swirling molten iron, no magnetic field. No magnetic field, nothing deflects the solar wind that then, literally, blows away any fledgling atmosphere. It's believed that Mars' atmosphere was considerably more dense than it is today, but along the way, its core cooled, and it lost its protective magnetic shield, allowing the solar wind to strip away much of its atmosphere.

kirillkh 9y ago
Then we have no hope of ever engineering Mars to have enough air for us to breath?
- LeifCarrotson 9y ago
  A Martian atmosphere (not sure about a lunar atmosphere) would be lost on a timescale of tens of millions of years. That's very quick in cosmological timescales, but slow enough that any human effort to create or replenish it could be very successful.
  - waegawegawe 9y ago
    That said, the earth's atmosphere has a mass of about five billion billion tons. For reference, as a species, we produce about ten billion tons of concrete each year. This is just to give a sense to the scale of effort involved in replacing a planetary atmosphere.
    - larkeith 9y ago
      Depending on the volume of surface ice (especially at the poles), might it be possible to produce atmosphere on a massive scale via orbital lenses or mirrors? With recent advances in solar sail technology, I can't imagine the implementation would be too far removed from current capabilities.
      - waegawegawe 9y ago
        Think about how large of a lens you're talking about. Even if it were one hundred meters across and was able to collect 100% of the sun's energy passing through it, the amount of energy produced would be utterly insignificant compared to the problem we're discussing. And how would you get a one hundred meter lens to mars orbit? Even after that, you have to consider that we want an oxygen atmosphere, not one made of water vapors. I don't know what you mean by "too far removed from current capabilities", but I doubt we'll even start working on the problem for two or three centuries. No, it seems more likely to me that we'd use our growing knowledge of genetics and psychology to hack out the part of ourselves that needs to be outside, and opt for a purely enclosed existence on Mars.
        kobeya 9y ago
        That's about ~250x the JWST. Given that we're talking about a society that has developed far enough to be sending people to Mars and terraforming the landscape, I don't think that 8 doublings would be an unreasonable multiplier of current capability. Still a flagship, many-decade mission though.
        LeifCarrotson 9y ago
        The James Webb mirror is a rigid, astonishingly precise focusing element. A solar energy mirror could instead be merely approximately parabolic, made of a foil instead of cryogenic, made of metalized kapton instead of gold-plated beryllium, would forego focusing elements, and so on. However, the thought of a telescope-quality mirror 250x the size of the JWST is pretty amazing :)
        larkeith 9y ago
        The IKAROS sail (launched 2010) is 196 m^2, using aluminum as a reflector (about 90% efficiency). With regards to transferring a lens to orbit, that is a self-solving problem - a large lens or mirror can both be used as a solar sail, potentially even hauling additional mass to Mars orbit. Mars receives 593 W/m^2 flux, so each IKAROS-sized reflector could produce about 100 KW of energy. Given the expected difficulty of large scale terraforming and colonization efforts, it seems the cost of, say, the equivalent of 10,000 IKAROS-sized mirrors (~1 GW, comparable to a large nuclear plant) would be relatively minor. Whether that would be more cost effective than shipping an equivalently powerful reactor or other generator is questionable - it will presumably depend on our lifting capacities.
    - kobeya 9y ago
      Also many thermoforming efforts consider adding an artificial dynamo (using, say, superconducting rings) to protect both the atmosphere and life on the surface. The energy cost of maintaining an artificial dynamo would be less than the incremental maintenance cost of maintaining atmosphere and dealing with health risks from radiation.
  - jlebrech 9y ago
    we could also use the resources on mars or the moon more sparingly, making dome bases would provide that. we could also bore into those tunnels and put caps on the hole afterward, have some of those channel light into those tunnels too.
  - deleted 9y ago
    [deleted]
- icanhackit 9y ago
  NASA proposes building artificial magnetic field to restore Mars’ atmosphere: https://www.universetoday.com/134052/nasa-proposes-magnetic-shield-protect-mars-atmosphere/ https://www.universetoday.com/134052/nasa-proposes-magnetic-...
  - extrapickles 9y ago
    Interesting, it only needs a 1-2 Tesla magnetic field. MRI machines go up to 3T, which means this isn't too outlandish with known technology. The main issue is that they probably want a Mars sized field at 1-2T.
    - andai 9y ago
      Does that mean it needs a bigger coil?
- larkeith 9y ago
  I don't know the rate of atmospheric loss, but it might be possible to introduce air at a high enough rate to outstrip the losses, making for a sustainable atmosphere. It would presumably depend on the availability of ice and other volatiles.
- abandonliberty 9y ago
  Unlikely because you can't use a noun as a verb :) Someday though we may be able to breathe on Mars
u801e 9y ago
I've read that it's the same case with Venus' core, but its atmosphere is far more dense than either Earth's or Mars'.
- Scaevolus 9y ago
  Venus has an induced magnetic field that may protect its atmosphere. https://www.astrobio.net/also-in-news/a-magnetic-surprise-from-venus/ https://www.astrobio.net/also-in-news/a-magnetic-surprise-fr...
  - nonbel 9y ago
    Apparently so does Mars though? http://www.sciencedirect.com/science/article/pii/S0019103509001316 http://www.sciencedirect.com/science/article/pii/S0019103509...
drdrey 9y ago
Even with a magnetic field, would the moon's gravity be sufficient to retain an atmosphere?
- SimbaOnSteroids 9y ago
  No, for that matter Mars doesn't have the gravity to retain an atmosphere either. I can't cite a source on this because I don't remember where I read it but I believe having a magnetic field surrounding a celestial body is a relatively minor factor in atmosphere retention compared to mass. If someone who specializes in planetary atmosphere retention knows better feel free to eviscerate me.
  - eradicatethots 9y ago
    >feel free to eviscerate me Off topic but I’d like it quite a lot if people could be informative without being eviscerating lol. I suppose this doesn’t usually happen, but it should happen more. That’d be so much better, so much more tolerable and happier. It’d be good for all of us probably lol.
    - averagewall 9y ago
      I think eviscerating comes when people present false statements as facts. Qualifying it with uncertainty as the OP did probably won't anger anybody. But telling lies because you don't know what you're talking about justifiably does.
      - brw12 9y ago
        You're pointing to an important difference: between being uninformed but trying to get towards being informed, and being uninformed but fiercely protective of your certainty. What Would Feynman Do? In this case, I'm imagining he'd say these are some of the things we think might explain bodies' keeping or losing atmosphere, but we have to remember that almost everything we think we know about planets and moons comes from looking at the light that bounces off of them and making guesses about the underlying rules, but we still don't know do much about the underlying rules of physics, so there's probably more that we don't know than what we do know about atmosphere retention.

kirillkh 9y ago

Then we have no hope of ever engineering Mars to have enough air for us to breath?

LeifCarrotson 9y ago
A Martian atmosphere (not sure about a lunar atmosphere) would be lost on a timescale of tens of millions of years. That's very quick in cosmological timescales, but slow enough that any human effort to create or replenish it could be very successful.
- waegawegawe 9y ago
  That said, the earth's atmosphere has a mass of about five billion billion tons. For reference, as a species, we produce about ten billion tons of concrete each year. This is just to give a sense to the scale of effort involved in replacing a planetary atmosphere.
  - larkeith 9y ago
    Depending on the volume of surface ice (especially at the poles), might it be possible to produce atmosphere on a massive scale via orbital lenses or mirrors? With recent advances in solar sail technology, I can't imagine the implementation would be too far removed from current capabilities.
    - waegawegawe 9y ago
      Think about how large of a lens you're talking about. Even if it were one hundred meters across and was able to collect 100% of the sun's energy passing through it, the amount of energy produced would be utterly insignificant compared to the problem we're discussing. And how would you get a one hundred meter lens to mars orbit? Even after that, you have to consider that we want an oxygen atmosphere, not one made of water vapors. I don't know what you mean by "too far removed from current capabilities", but I doubt we'll even start working on the problem for two or three centuries. No, it seems more likely to me that we'd use our growing knowledge of genetics and psychology to hack out the part of ourselves that needs to be outside, and opt for a purely enclosed existence on Mars.
      - kobeya 9y ago
        That's about ~250x the JWST. Given that we're talking about a society that has developed far enough to be sending people to Mars and terraforming the landscape, I don't think that 8 doublings would be an unreasonable multiplier of current capability. Still a flagship, many-decade mission though.
        LeifCarrotson 9y ago
        The James Webb mirror is a rigid, astonishingly precise focusing element. A solar energy mirror could instead be merely approximately parabolic, made of a foil instead of cryogenic, made of metalized kapton instead of gold-plated beryllium, would forego focusing elements, and so on. However, the thought of a telescope-quality mirror 250x the size of the JWST is pretty amazing :)
      - larkeith 9y ago
        The IKAROS sail (launched 2010) is 196 m^2, using aluminum as a reflector (about 90% efficiency). With regards to transferring a lens to orbit, that is a self-solving problem - a large lens or mirror can both be used as a solar sail, potentially even hauling additional mass to Mars orbit. Mars receives 593 W/m^2 flux, so each IKAROS-sized reflector could produce about 100 KW of energy. Given the expected difficulty of large scale terraforming and colonization efforts, it seems the cost of, say, the equivalent of 10,000 IKAROS-sized mirrors (~1 GW, comparable to a large nuclear plant) would be relatively minor. Whether that would be more cost effective than shipping an equivalently powerful reactor or other generator is questionable - it will presumably depend on our lifting capacities.
  - kobeya 9y ago
    Also many thermoforming efforts consider adding an artificial dynamo (using, say, superconducting rings) to protect both the atmosphere and life on the surface. The energy cost of maintaining an artificial dynamo would be less than the incremental maintenance cost of maintaining atmosphere and dealing with health risks from radiation.
- jlebrech 9y ago
  we could also use the resources on mars or the moon more sparingly, making dome bases would provide that. we could also bore into those tunnels and put caps on the hole afterward, have some of those channel light into those tunnels too.
- deleted 9y ago
  [deleted]
icanhackit 9y ago
NASA proposes building artificial magnetic field to restore Mars’ atmosphere: https://www.universetoday.com/134052/nasa-proposes-magnetic-shield-protect-mars-atmosphere/ https://www.universetoday.com/134052/nasa-proposes-magnetic-...
- extrapickles 9y ago
  Interesting, it only needs a 1-2 Tesla magnetic field. MRI machines go up to 3T, which means this isn't too outlandish with known technology. The main issue is that they probably want a Mars sized field at 1-2T.
  - andai 9y ago
    Does that mean it needs a bigger coil?
larkeith 9y ago
I don't know the rate of atmospheric loss, but it might be possible to introduce air at a high enough rate to outstrip the losses, making for a sustainable atmosphere. It would presumably depend on the availability of ice and other volatiles.
abandonliberty 9y ago
Unlikely because you can't use a noun as a verb :) Someday though we may be able to breathe on Mars

u801e 9y ago

I've read that it's the same case with Venus' core, but its atmosphere is far more dense than either Earth's or Mars'.

Scaevolus 9y ago
Venus has an induced magnetic field that may protect its atmosphere. https://www.astrobio.net/also-in-news/a-magnetic-surprise-from-venus/ https://www.astrobio.net/also-in-news/a-magnetic-surprise-fr...
- nonbel 9y ago
  Apparently so does Mars though? http://www.sciencedirect.com/science/article/pii/S0019103509001316 http://www.sciencedirect.com/science/article/pii/S0019103509...

drdrey 9y ago

Even with a magnetic field, would the moon's gravity be sufficient to retain an atmosphere?

SimbaOnSteroids 9y ago
No, for that matter Mars doesn't have the gravity to retain an atmosphere either. I can't cite a source on this because I don't remember where I read it but I believe having a magnetic field surrounding a celestial body is a relatively minor factor in atmosphere retention compared to mass. If someone who specializes in planetary atmosphere retention knows better feel free to eviscerate me.
- eradicatethots 9y ago
  >feel free to eviscerate me Off topic but I’d like it quite a lot if people could be informative without being eviscerating lol. I suppose this doesn’t usually happen, but it should happen more. That’d be so much better, so much more tolerable and happier. It’d be good for all of us probably lol.
  - averagewall 9y ago
    I think eviscerating comes when people present false statements as facts. Qualifying it with uncertainty as the OP did probably won't anger anybody. But telling lies because you don't know what you're talking about justifiably does.
    - brw12 9y ago
      You're pointing to an important difference: between being uninformed but trying to get towards being informed, and being uninformed but fiercely protective of your certainty. What Would Feynman Do? In this case, I'm imagining he'd say these are some of the things we think might explain bodies' keeping or losing atmosphere, but we have to remember that almost everything we think we know about planets and moons comes from looking at the light that bounces off of them and making guesses about the underlying rules, but we still don't know do much about the underlying rules of physics, so there's probably more that we don't know than what we do know about atmosphere retention.