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Would 1/5Th Atmosphere On Mars Protect From Radiation?


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Hi all,

I asked some people on another forum whether a post-terraformed Mars would require a magnetic field to protect Elon Musk's bold new Martians (  :bow:  :bow:  :bow: ) from radiation, both solar and cosmic. These are some of their replies, and not being technical myself, I wonder if you could check their working? If the claims below are true, then we "only" need to cook the CO2 poles and then Mars will have enough atmosphere to avoid a space suit (but wearing very warm clothes with breather mask), start growing some crops on the surface without habitat domes, AND be protected from radiation.

 

So, 2 questions:-

 

1. Do the two people below speak the truth? Would 20% of earth's atmospheric pressure protect Martians from radiation?

2. How would YOU recommend they warm the planet?

 

First person:

 

As long as the air pressure at the surface post-terraforming is at least 0.2 atmospheres, it will provide adequate radiation shielding (over 5000 kg per square meter column density). This also happens to be about the minimum air pressure that would allow us to walk around outside without pressure suits, just wearing oxygen masks so we can breathe. And there's believed to be enough carbon dioxide frozen on Mars to make the atmosphere at least that thick.

So despite the popular misconception, a magnetic field is not at all necessary to protect the surface of a terraformed Mars from radiation.

 

https://en.wikipedia.org/wiki/Health_threat_from_cosmic_rays#Shielding

a NASA design study for an ambitious large spacestation envisioned 4 metric tons per square meter of shielding to drop radiation exposure to 2.5 mSv annually (± a factor of 2 uncertainty), less than the tens of millisieverts or more in some populated high natural background radiation areas on Earth

So 4 metric tons of shielding per square meter is enough. Earth's atmosphere has a column density of 10 metric tons per square meter, so we just need 40% of that. At 1 g, 40% of the column density would have a pressure of 0.4 atmospheres, but Mars has a surface gravity of 0.38 g so the air pressure would be 0.4 * 0.38 = 0.15 atmospheres. So 0.2 atm should be more than enough for shielding, and it's just enough for the 0.2 atm partial pressure of oxygen we breathe.
https://www.reddit.com/r/Mars/comments/57eqq2/will_atmosphere_on_mars_reduce_radiation_to/

 

 

 

 

Second person:

These values are from a bar graph with a logarithmic scale that I copied from some website over a year ago.

Annual Cosmic Radiation (Sea Level) 0.3 milliSieverts
US Annual Average, All Sources 4 mSv
Abdominal CT Scan 8 mSv
DOE Radiation Worker Annual Limit 20 mSv
6 Months on ISS (average) 80 mSv
180 day Transit to Mars 300 mSv
500 days on Mars 300 mSv

From this you can see that the Earth’s magnetic field ( and maybe having the earth blocking radiation from one side) cuts radiation dose on the ISS compared to interplanetary space. However, you can see that the mass of the atmosphere does most of the shielding for the surface of the earth.

The value for the stay on Mars must ignore the effect of piling dirt on the habitat.

Since the gravity of Mars is .4 of Earth gravity it would take 2.5 times the mass per area of atmosphere to give 1 atmosphere pressure on Mars. So the radiation shielding of a thickened martian atmosphere would be plenty.
https://bravenewclimate.com/2016/09/10/open-thread-26/#comment-464893

 

 

 

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Hi all,

I asked some people on another forum whether a post-terraformed Mars would require a magnetic field to protect Elon Musk's bold new Martians from radiation, both solar and cosmic. These are some of their replies, and not being technical myself, I wonder if you could check their working? If the claims below are true, then we "only" need to cook the CO2 poles and then Mars will have enough atmosphere to avoid a space suit (but wearing very warm clothes with breather mask), start growing some crops on the surface without habitat domes, AND be protected from radiation.

 

So, 2 questions:-

 

1. Do the two people below speak the truth? Would 20% of earth's atmospheric pressure protect Martians from radiation?

2. How would YOU recommend they warm the planet?

It will certainly decrease risk from radiation.  It will not be as low as the surface of Earth, but it will certainly not be lethal.

 

Easiest way to warm the planet is to use in-situ sources of gas.

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So if that's for real, it seems that there would be a bunch of reasons to thicken the atmosphere as soon as we determine there's no native life to worry about.

 

1. Radiation protection! We wouldn't need magnetosphere to protect us as one fifth atmospheric pressure is enough to bring the surface radiation down to safe levels.

 

2. Clothes! Dump clunky vacuum pressure-suits and just wear normal warm clothes! (With an oxygen mask of course, just like on a high mountain).

 

3. Farming! Some agriculture could begin on the Martian surface, without pressure domes.

 

4. Easier construction! Habitats don't have to be sealed against vacuum outside: 20% Earth's atmosphere is far easier to build for. Protection, clothes, farming, and easier habitats. That's what warming the poles would allow! And 20% is just the beginning. Mars has all the atmosphere we could want to manufacture locked away in its surface if we mine it long enough.

 

5. Easier landing, saving fuel and possibly cutting the number of refuelling trips Space X have to make to the Mars Colonial Transport.

6. Starts to prepare the planet for a breathable atmosphere.

 

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