Mars Radiation

[Yggdrasill]

By far the biggest risk of something like that is to electronics. The radiation dose of 20-50mSv or so isn't lethal, but melting electronics, upon which Mars would be especially dependent on, very likely would be.

I'd agree that this might be a bigger concern.

I'm not so sure that it would be a huge issue on Mars though. The amount of energetic particles on the Martian surface is pretty low compared to in space during energetic solar particle events. And it's nothing compared to the Van Allen belts and the radiation belts of Jupiter.

Very much can be done through clever engineering. Machines can be designed for the environment, humans cannot.

[Yggdrasill]

I agree. It depends on how the risk is perceived.

Jiggens et al. (2014) observed that the largest known CME, the 1959 “Carrington event” was unusually fast and took 17.5 hrs to each Earth.  While unshielded astronauts would receive over 1.2 Sv in such an event, those behind 40 g/cm2 of shielding would receive only 0.1 Sv. Mars surface values were not calculated, but would probably be about half this dose.

Do you have modelled numbers for a Mars surface dose?

Jiggens, P., Chavy-Macdonald, M. A., Santin, G., Menicucci, A., Evans, H., and Hilgers, A. 2014. The magnitude and effects of extreme solar particle events. Journal of Space Weather and Space Climate 4, A20, DOI: https://doi.org/10.1051/swsc/2014017.

Here: https://www.irpa.net/members/TS10a.2.pdf

I did have it in the sources page at the end of the video, but it sort of ends up behind the suggested videos. For the future I guess I could use two slides, and leave the top half blank. Probably better. (Note that I don't use almost any figures directly from any source. I have made some assumptions of my own.)

[rfdesigner]

By far the biggest risk of something like that is to electronics. The radiation dose of 20-50mSv or so isn't lethal, but melting electronics, upon which Mars would be especially dependent on, very likely would be.

I'd agree that this might be a bigger concern.

I'm not so sure that it would be a huge issue on Mars though. The amount of energetic particles on the Martian surface is pretty low compared to in space during energetic solar particle events. And it's nothing compared to the Van Allen belts and the radiation belts of Jupiter.

Very much can be done through clever engineering. Machines can be designed for the environment, humans cannot.

Rad hardening is what you do, things like adding in discharge paths, error correction, picking one transistor class over another and so on.  You end up with chips that tend to be a little less dense as they have additional or larger structures, but they're reliable for a much much longer period of time in deep space.

See voyager I & II for early examples that REALLY work, decades of functionality has already been done, what you can't do it take a Laptop you bought from your local Tech-Store, well you can, but it might not last.

Yes rad hardened electronics is more expensive, primarily because the market size is tiny.  Make more stuff all using the same designs and the cost per chip will drop like a stone.

[LMT]

...you could have seven Starship placed close to one another. Then fill the center Starship all the way with water. You now have six Starships where one side blocks radiation with a (up to) 9 meter deep water column, and the other Starships would also help.

No, shielding is needed above, and hulls don't help.

The radiation is omnidirectional, so having shielding in any direction helps reduce radiation.

The most interesting thing I came across while researching is the fact that it helps even having water shielding *below* you. Merely being in the vicinity of water and other light materials helps, because there is less scattered secondary radiation. You can see this in the graphs at 24:30 in the video. The radiation up to around 40 km above the surface is affected by the the surface material. I could have mentioned it in the video, but placing your habitat on top of a glacier could help substantially!

And the hulls did help in your source, by 10%. And six ~200 ton Starships would help more.

Note persistent Martian doses, on and below the surface.  Paris et al. 2019.  20 mSv / year is the longstanding target limit.

1 2 3

Refs.

Paris, A.J., Davies, E.T., Tognetti, L. and Zahniser, C., 2019. Prospective Lava Tubes at Hellas Planitia. Journal of the Washington Academy of Sciences, 105(3), pp.13-36.

No, GCRs are not omnidirectional on the surface.  That's why no design places, e.g., water underneath.

Re: hulls, no, the 10% cut wasn't helpful, hence, "a non-starter for in-transit space travel".

Rules like 20 mSv are subject to revision.

Don't fabricate stories; just learn about the topic.

[spacenut]

I've mentioned this before.  Build your habitats under water storage.  Storing water above habitats with about 1m or 3' of water should block out most of the radiation.  Elevated water also allows for water pressure for potable water without constant pumping.  Sure the structure has to be strong enough to hold the water, but if it is built in glass or plexiglass or transparent aluminum daylight can shine through this water to allow light into various buildings.  I know Mars is cold, but LED lighting with some heat should keep the water from freezing. 

Of course, another is to cover habitats with soil or regolith which insulates from cold as well. 

Certain plastics as well as the hydrogen in water protects from radiation. 

Going out exploring in EV suits will be the time of most exposure.  Well designed rovers can allow a lot of protection. 

Again, 0.38g is the only real unknown for long term colonization.  Since SpaceX is going to go to Mars during a 6 month synod when Mars is closest to earth, and not in the 18 months when Mars is further away.  Seems like a 2 year rotation can give a lot of information back for several years, to determine permanent settlement options. 

[LMT]

Rad hardening is what you do, things like adding in discharge paths, error correction, picking one transistor class over another and so on.

Some history and comparisons:

Space-grade CPUs: How do you send more computing power into space?

Figuring out radiation was a huge "turning point in the history of space electronics."

Jacek Krywko - 11/11/2019

[joek]

...
See voyager I & II for early examples that REALLY work, decades of functionality has already been done, what you can't do it take a Laptop you bought from your local Tech-Store, well you can, but it might not last.
...

Blast from the past. I remember that as it was quite the crash program. See Voyager electronic parts radiation program, volume 1; from pg. 77-41:

In the Voyager program, as mentioned earlier, radiation was originally not considered to be a problem. Subsequently, Pioneer Jupiter flybys indicated the presence of strong radiation belts [understatement of the year], which led to an intensive program to harden the existing Mariner design.

(I worked on the Pioneers, not the Voyagers, but there was quite a bit of exchange between the two teams as you might imagine.)

edit: p.s. Mariner 10/11 morphed into Voyager 1/2.

[Twark_Main]

if all the cliffs are unstable, you can just ensure that the habitat is set up outside the expected landslide path, for a bit lower shielding effect, but still some shielding, if the cliffs are within view.

In low gravity and atmosphere, the landslides can travel tens of kilometers. So your setback distance has to be at least that far.

Doing the trigonometry, I don't think you'll be able to achieve any meaningful level of shielding this way.

The actively degrading cliffs we have seen on Mars to date have all been in polar areas with instability driven by sublimation of dry ice.  This is not going to be a global problem. 

Cliff dwelling on Earth are all in areas of structural stability.  Why should these not exist on Mars?  We already know that landscape degradation is very slow in most places on Mars.

Photos from Setenil (Spain), a town of several thousand inhabited for centuries.

I can't help noticing that the surface is stabilized by a bunch of vegetation...   


That's a "con" for Mars. In the "pro" column, there's no (meaningful amount of) running water, other than the extremely occasional recurring slope lineae which may result from deliquescence.

In the "pro" column for Mars is also.....    no vegetation.   Roots and soil can stabilize the land, but they can also split rocks and dissolve minerals.

[Twark_Main]

The most interesting thing I came across while researching is the fact that it helps even having water shielding *below* you. Merely being in the vicinity of water and other light materials helps, because there is less scattered secondary radiation. You can see this in the graphs at 24:30 in the video. The radiation up to around 40 km above the surface is affected by the the surface material. I could have mentioned it in the video, but placing your habitat on top of a glacier could help substantially!

Yes, when I read the (excellent) paper that graph comes from, I immediately though of paving Mars roads with polyethylene-stabilized regolith "concrete." 

Binder and extra shielding for vehicles driving on top!

[Dalhousie]

I agree. It depends on how the risk is perceived.

Jiggens et al. (2014) observed that the largest known CME, the 1959 “Carrington event” was unusually fast and took 17.5 hrs to each Earth.  While unshielded astronauts would receive over 1.2 Sv in such an event, those behind 40 g/cm2 of shielding would receive only 0.1 Sv. Mars surface values were not calculated, but would probably be about half this dose.

Do you have modelled numbers for a Mars surface dose?

Jiggens, P., Chavy-Macdonald, M. A., Santin, G., Menicucci, A., Evans, H., and Hilgers, A. 2014. The magnitude and effects of extreme solar particle events. Journal of Space Weather and Space Climate 4, A20, DOI: https://doi.org/10.1051/swsc/2014017.

Here: https://www.irpa.net/members/TS10a.2.pdf

I did have it in the sources page at the end of the video, but it sort of ends up behind the suggested videos. For the future I guess I could use two slides, and leave the top half blank. Probably better. (Note that I don't use almost any figures directly from any source. I have made some assumptions of my own.)

Most helpful, thank you.  Unfortunately the full citation at the end of your video is covered by ads for additional videos.  Could you give this please (via PM is OK).

[Twark_Main]

I agree. It depends on how the risk is perceived.

Jiggens et al. (2014) observed that the largest known CME, the 1959 “Carrington event” was unusually fast and took 17.5 hrs to each Earth.  While unshielded astronauts would receive over 1.2 Sv in such an event, those behind 40 g/cm2 of shielding would receive only 0.1 Sv. Mars surface values were not calculated, but would probably be about half this dose.

Do you have modelled numbers for a Mars surface dose?

Jiggens, P., Chavy-Macdonald, M. A., Santin, G., Menicucci, A., Evans, H., and Hilgers, A. 2014. The magnitude and effects of extreme solar particle events. Journal of Space Weather and Space Climate 4, A20, DOI: https://doi.org/10.1051/swsc/2014017.

Here: https://www.irpa.net/members/TS10a.2.pdf

I did have it in the sources page at the end of the video, but it sort of ends up behind the suggested videos. For the future I guess I could use two slides, and leave the top half blank. Probably better. (Note that I don't use almost any figures directly from any source. I have made some assumptions of my own.)

Most helpful, thank you.  Unfortunately the full citation at the end of your video is covered by ads for additional videos.  Could you give this please (via PM is OK).

I always forget that people see those. I have my ad blocker configured to hide them. 

[LMT]

The most interesting thing I came across while researching is the fact that it helps even having water shielding *below* you. Merely being in the vicinity of water and other light materials helps, because there is less scattered secondary radiation. You can see this in the graphs at 24:30 in the video. The radiation up to around 40 km above the surface is affected by the the surface material. I could have mentioned it in the video, but placing your habitat on top of a glacier could help substantially!

Yes, when I read the (excellent) paper that graph comes from, I immediately though of paving Mars roads with polyethylene-stabilized regolith "concrete." 

Binder and extra shielding for vehicles driving on top!

The numbers tell a different story.

Site elevation, not water content, has the main surface effect.  Down on Hellas Planitia, annual surface dose is ~ 125 mSv/yr.  1 2

Compare with "icy" Arabia Terra, higher up, Fig. 6.  What do we see?

Even on Hellas Planitia, overhead shielding would be paramount.  --  How deep are lava tubes, btw?

[Robotbeat]

Yeah, people often underestimate how effective Mars’ atmosphere is at shielding.

At low altitudes it should have an effective thickness of over 40 grams/cm^2 of CO2 due to the slant angle most radiation would have to travel through, and CO2 is a much better shield than aluminum.

rem is the same as cSv, or 10mSv.

[Yggdrasill]

The numbers tell a different story.

Site elevation, not water content, has the main surface effect.  Down on Hellas Planitia, annual surface dose is ~ 125 mSv/yr.  1 2

Compare with "icy" Arabia Terra, higher up, Fig. 6.  What do we see?

Even on Hellas Planitia, overhead shielding would be paramount.  --  How deep are lava tubes, btw?

In figure 6, all the different surface materials assume the same atmospheric shielding, at 21 grams/cm^2.

And wouldn't you know it, the first three are arranged by water content, while the dry materials are fairly similar, except for sulphur concrete, which was a bit better than the other options.

If you look at radiation measurements from MARIE and the like, yes, elevation is the major differing factor. But at the same time, water content is also thought to be largely determined by elevation. With more atmospheric pressure, you have less sublimation. So, we don't have the full picture of what we are actually measuring; effects from atmospheric shielding, or effects from water content.

[LMT]

...we don't have the full picture of what we are actually measuring; effects from atmospheric shielding, or effects from water content.

Look at the MARIE map estimate.  Does dose track elevation globally or not?  What do you see at the poles?

[Yggdrasill]

Actually, when I look a bit closer at the source, I believe the data isn't usable for this purpose.

In the way elevation data and radiation data has been merged, I believe we are mostly seeing the elevation data. (And yes, elevation is strongly correlated with elevation!) I believe the MARIE data is much lower resolution than the elevation data, maybe even to an extent that a very similar map could be produced by multiplying elevation data with a single value for the average radiation level. I would like to see a map of only the radiation measurements, not merged with elevation data, just to get an idea of what detail, if any, it is possible to discern. Though I haven't been able to find such a map. (Anyone know if such a map exists?)

Another aspect is that most of the secondary radiation generated by GCRs striking the surface wouldn't reach MARIE. The atmospheric shielding attenuates the secondary radiation to almost nothing, as can be seen in figure 6. At an altitude of 80 km, the difference in radiation is only 12%, while on the surface, the difference is around 45%.

Measuring a small variation with poor resolution would make it very difficult to distinguish any detail from noise.

[LMT]

Actually, when I look a bit closer at the source, I believe the data isn't usable for this purpose.

In the way elevation data and radiation data has been merged, I believe we are mostly seeing the elevation data. (And yes, elevation is strongly correlated with elevation!) I believe the MARIE data is much lower resolution than the elevation data, maybe even to an extent that a very similar map could be produced by multiplying elevation data with a single value for the average radiation level. I would like to see a map of only the radiation measurements, not merged with elevation data, just to get an idea of what detail, if any, it is possible to discern. Though I haven't been able to find such a map. (Anyone know if such a map exists?)

Another aspect is that most of the secondary radiation generated by GCRs striking the surface wouldn't reach MARIE. The atmospheric shielding attenuates the secondary radiation to almost nothing, as can be seen in figure 6. At an altitude of 80 km, the difference in radiation is only 12%, while on the surface, the difference is around 45%.

Measuring a small variation with poor resolution would make it very difficult to distinguish any detail from noise.

You're exaggerating the neutron effect.  Mistakes chase your wish:

My biggest concern is the idea that we *have to* live underground if we go to Mars. If it is treated as a necessity, it imposes huge restrictions on any mission going to Mars. As well as any future base or settlement. 

Shielding requirement is nothing new, Yggdrasill.

Small above-ground neutron differences from water are expected, but no substitute for shielding, as we saw; hence the meaningful mapped dose estimate, and ongoing interest in low-elevation lava tubes.

Do you understand why ions, rather than fast neutrons, pose the main threat?

[ccdengr]

I believe the MARIE data is much lower resolution than the elevation data... I would like to see a map of only the radiation measurements, not merged with elevation data, just to get an idea of what detail, if any, it is possible to discern. Though I haven't been able to find such a map. (Anyone know if such a map exists?)

MARIE was just measuring the isotropic radiation seen in orbit (MARIE wasn't even pointed at the surface), and not at a very high time resolution, so such a map wouldn't show much of anything.  The maps you see are made by taking the average dose in orbit and modulating it with a model of atmospheric absorption.

You can find the raw MARIE data here: https://pds-ppi.igpp.ucla.edu/search/?filter=ODMA&title=Mars%20Odyssey%20Data%20Holdings

[Yggdrasill]

MARIE was just measuring the isotropic radiation seen in orbit (MARIE wasn't even pointed at the surface), and not at a very high time resolution, so such a map wouldn't show much of anything.  The maps you see are made by taking the average dose in orbit and modulating it with a model of atmospheric absorption.

You can find the raw MARIE data here: https://pds-ppi.igpp.ucla.edu/search/?filter=ODMA&title=Mars%20Odyssey%20Data%20Holdings

That's basically what I thought. I was going to dig a bit more into what data was gathered and how it was processed, but thanks for saving me that work!

So yeah, the map just doesn't contain the information needed to say anything about the effects of water prevalence on radiation conditions, because the levels are simply approximated based on elevation.

[Robotbeat]

I just want to address something here. The Mars radiation dose rate at likely landing site altitudes, like those of MSL Curiosity which carries a radiation dosimeter (which can also measure the radiation quality factor, which happens to be virtually identical between ISS and the Martian surface…2.2 and 2.6 respectively) show a radiation level the same as inside ISS, which has a similar radiation dosimeter. 0.213mGray/day Mars Vs 0.240mGray/day ISS. 201mSv/year (full time on the surface) Mars and 193mSv/year *inside* ISS using the respective quality factors.

The dose is pretty small. So much so that as long as you spend no more than 41 hours a week outside of thick shielding, your dose won’t exceed 50mSv/year, which is the terrestrial radiation worker dose rate limit.

The average American spends 93% of their life inside. Meaning less than 12 hours per week outside. This would mean just a 14mSv/year dose from spending the average time outside. This is a tiny dose, about the same amount that the average resident of South Dakota experiences (when you include medical imaging… which is around 3-4mSv/year average, plus 9mSv/year Radon and 1mSv/year other sources).

So you can spend more than three times as much time outside as the average American without exceeding the 50mSv/day terrestrial radiation worker dose rate limit, not to mention the much higher dose rate we allow for astronauts.

This idea that Mars astronauts would be trapped underground all the time due to radiation risk is just not true. They could spend just as much time outdoors as the average American and do just fine as far as dose limits are concerned.

Source for graph and figures (ISS quality factor comes from something else, but you can basically infer it from stuff here): https://www.nasa.gov/sites/default/files/atoms/files/mars_radiation_environment_nac_july_2017_final.pdf