Mars radiation a serious risk to astronauts. - Is radiation a surmountable problem?

Bill White · 2003-03-14 11:39:24

There seems to be some "spinning" going on here. . .

30 minutes ago - while driving - I heard a CBS radio report saying that Mars was very unsafe to even visit and no one should ever want to live there.

Just now I went to Space.com and they say the radiation is high but can be managed.

I have always liked Zubrin's idea of putting sandbags on top of the habitat - Keep It Simple!

A one-two punch of Columbia AND a widespread public belief that Mars is not a safe place to go and maybe "humans in space" end up being in big trouble. Clarification --> civilian humans in space gets cancelled. Military humans in space is funded as needed for national defense.

Bill White · 2003-03-14 14:05:54

AP Falsely Reports Mars Radiation Data

This is the heading of an e-mail I just received from the Mars Society.

I am reminded of a cartoon I saw once. Twelve jurors are sitting in total shock with their hair standing straight up. The judge says, "Please disregard and ignore that last comment."

Yeah - right. The damage has been done no matter what retractions or corrections are later published.

Byron · 2003-03-14 14:18:59

AP Falsely Reports Mars Radiation Data
This is the heading of an e-mail I just received from the Mars Society.
I am reminded of a cartoon I saw once. Twelve jurors are sitting in total shock with their hair standing straight up. The judge says, "Please disregard and ignore that last comment."
Yeah - right. The damage has been done no matter what retractions or corrections are later published.

Well, considering that people have a short memory with this kind of stuff, hopefully the "false" report will be forgotten in the near future....

You have to wonder sometimes, however, if there are some folks out there who really don't want to see humans-on-Mars... ???

B

RobertDyck · 2003-03-14 17:12:49

The radiation exposure reported today does refer to radiation observed in orbit. Of course it will be larger than the ISS; Earth has a magnetosphere that protects our planet from much of the radiation. The radiation belts of the magnetosphere are in medium orbit, so anything in high Earth orbit is outside the protection, but low Earth orbit is within that protection. The ISS is in low orbit. Mars does not have a magnetosphere.

The question for Mars explorers is the radiation dose on the surface. On March 1, 2002, NASA released its estimate of surface radiation based on orbital radiation observed by Odyssey and their estimate of ability of Mars atmosphere to block it. The result was Estimated Radiation Dosage on Mars. Compare this with the March 13, 2003, release of Comparison of Martian Radiation Environment with International Space Station. The new chart is measured in millisieverts/day while the surface radiation estimate is in rems/year. 1 sievert is 1,000 millisievert, and 1 sievert is 100 rem. The pale blue areas of the surface map indicate 15 rems/year or an average of 0.41 millisieverts/day. This is below the average at ISS.

The solution to mediating the risk of radiation exposure for a manned mission to Mars is just what Robert Zubrin has been saying all along: get to Mars quick and down on the surface where it is safe.

RobS · 2003-03-14 19:22:27

I think this is good news. The estimated radiation dosage on Mars website Robert Dyck gives says the radiation on the surface is 10 to 20 rems per year (less at low altitudes; more on top of the mountains) and the International Space Station is 20-40 per year. So the surface is half as "dangerous" as low earth orbit. Furthermore, Zubrin in *The Case for Mars,* page 118, says the radiation on the surface of Mars is 9 rems per year, which is very good agreement with the 10 rem figure for the lowlands (where a mission would land). He also says sandbags would reduce the interior dosage to 6 rems per year, and with a lot of EVAs the average dosage would be 7 rems per year.

The lifetime limit for NASA I think is about 100 rems. By this measure, someone could stay on Mars 14 years; probably more if the habitat were shielded under a few meters of regolith.

As for the negative "spin," that's just reporters making the headline of the article attractive to the average reader. It won't be noticed by the people who make decisions.

-- RobS

dickbill · 2003-03-14 21:19:32

The high radiation load is certainly not a good news. But it can been dealed with. First, protect the astronauts from the radiations by shielding of course. Second they have to be checked personnaly and for cancer family history to assess some particular risks. Before the flight, they make frozen samples of their blood and bone marrow to deal with possible leukemia, or semen/eggs if they want to have children after the flight.
They can also bring some fresh frozen blood of their own, protected from radiations, on the trip to mars, just in case. But if they get some fulgurant leukemia or anemia during the trip, I doubt that might be enough, so they will have drugs available as well. I think a doctor should be part of the crew.
The trip designed by Zubrin is for a maximum of 1 year spent on Mars, is that right ? Metastasis don't develop in one day, this mean that any sign of anemia related sickness detected on Mars will probably appears after several months on the martian surface and will be treated on earth, most likely.
The litterature on the Chernobyl accident is still growing but it suggests that the astronaut might expect some long term effects difficult to predict other than with a statistical chance. Not necesseraly lethal effects, like cataract, but still. On Mars the "today's radiation" is as important as the weather. Nobody get ouside without an umbrella when it's raining, it's not really different with the radiations.
And also, the sun is about 12 minutes light-speed far from Mars, so the astronauts can be warned a little bit in advance of the solar particle storms.

Shaun Barrett · 2003-03-17 01:53:31

The journalists responsible for inaccurate overdramatisation of radiation data which might lead to the abandonment of Mars colonisation efforts will be first up against the wall when the revolution comes!!
:angry:

By the way, can anyone remember whether Dr. Zubrin gave estimates of surface radiation dosages after the establishment of a 500 millibar CO2 atmosphere?
???

Palomar · 2003-03-26 13:53:07

*Getting out of my league here (and yes, I've read the chapter in _The Case for Mars_ which addresses radiation), but...here goes (fumbling attempt):

I was surprised to read one of our regulars here saying he was doubtful any human could live on Mars long-term, and that perhaps only short-term stays were possible. I cannot find the thread again, and I don't want to call out a name (though I'm pretty sure I recall who). His saying this surprised me.

As regards the news source responsible for the news article which was posted to the Mars Society web page (dangerous radiation), yes there could be an anti-human-exploration agenda at play, although it could also simply have been human error. But, no disrespect intended of course, we could be accused of wanting to "tweak" radiation data to our benefit.

What exactly IS the radiation danger on Mars? And how many of you folks (more knowledgeable than me in this regard, obviously) think humans can live for long periods of time on Mars (even a lifetime) versus humans only being able to stay for short durations (perhaps up to 5 years, for example)?

I ask, because the one member of our group here who seemed to be having second thoughts and changing his mind is knowledgeable and I respect his well-reasoned viewpoints...and his musings in this regard kind of threw me.

Just wondering.

--Cindy

Phobos · 2003-03-26 14:06:37

What exactly IS the radiation danger on Mars? And how many of you folks (more knowledgeable than me in this regard, obviously) think humans can live for long periods of time on Mars (even a lifetime) versus humans only being able to stay for short durations (perhaps up to 5 years, for example)?

Humans who live for a lifetime on Mars will probably have to live underground to minimize their radiation exposure. NASA only allows its astronauts to accumulate only so many rems before they're retired from spaceflight and if those standards remain, any astronauts going to Mars won't be allowed to go back into space because they will have reached the maximum allowed exposure by the time they return. I'm holding out hope though that we might develop "force fields" which can block radiation. People are doing research on this sort of thing at the moment so no telling what we may have in 30 years.

dickbill · 2003-03-26 14:55:33

I've also read that there is some small, very local, but strong magnetic fields on Mars. Remnants of the ancient global magnetic field. These small fields can create a small efficient magnetosphere against the radiations, unfortunatly, from the map I can remember, they are almost all in the highlands southern, So their protection cannot be cumulated with the atmosphere thickness. annoying...

Shaun Barrett · 2003-03-26 19:53:03

You're right, Dickbill.
The remnant crustal magnetic fields on Mars are stronger and more extensive in the higher, cratered southern regions than in the northern lowlands or in Hellas.
This makes it impossible, as you mentioned, to take advantage of both magnetic and atmospheric shielding at the same time.

For an interesting article (not new, but still good reading! ), try this site.
It seems there are at least some places on Mars where there's complete shielding from the solar wind. But it doesn't look like this will be helpful for exploration or settlement, since we can hardly confine ourselves to these small areas simply to avoid charged particles from the Sun. If we're going to be that worried about radiation, our best bet is to just stay home!!
Apparently, though, there are places between the strips of magnetised crust where the solar wind is channeled straight down onto the surface! My assumption is that these particular zones would have a higher than average flux of charged particles from the Sun and would be places for explorers to avoid.

The consensus of opinion among those who ought to know, e.g. Dr Zubrin, is that radiation exposure can be minimised by keeping Earth-Mars transit times short and using regolith or natural caves for shielding down on the surface. Air-shielding under large domes or in tented valleys will be helpful in the medium/long term, while eventually a planetwide thicker atmosphere would be ideal.

I haven't been able to find projections for the rems/year new Martians can expect to receive after we establish an atmosphere of, say, 500 millibars of CO2. (If that's possible.)
That information will give us a much better idea of how colonists will ultimately fare in the new world.
???

RobS · 2003-03-28 11:24:03

Five hundred millibars of pressure is about the same as on the Earth at what; maybe 17,000 feet? People do live at those altitudes without trouble, and airplane pilots fly much higher than that for their entire career.

-- RobS

dicktice · 2003-03-29 10:26:48

No reason why pressure domes above habitats (canopies covering craters, say, or ravines) can't be multi-layered and filled with gas(s) to provide UV-absorption as well as visible light-transmission characteristics. Just a hint, to get us started. Want to discuss this further--if only to refute the alternative, as opposed to the requirement for a planetary magnetic field (!) generated essentially from scratch...?

RobertDyck · 2003-03-29 11:31:59

Polyvinyl butyral (PVB) is a plastic that absorbs 99% of UV light. It is used to make laminated glass, such as the safety glass in your car's windshield. Actually, if all windows in your car were laminated glass, the PVB would prevent UV from damaging your upholstery. However, there is another product applicable to Mars. Spectrally selective window coatings reflect IR and UV light while letting visible light through. This permits sunlight to get in, but radiant heat cannot get out. Heat Mirror is a commercial brand name for such a window coating, and it is available as an applied film under the names Solis and V-Kool. The spectrum shows it blocks 98% of UVB and UVC, but UVA (close to visible light) tapers from 15% blocking where the frequency is on be boundary between UVA and violet light, and 98% blocking at higher frequency, close to UVB. Spectrally selective coatings, including the coatings used for Solis and V-Kool, are silver based compounds. One study in Alaska found that plants grown in a greenhouse with UV light filtered out grew faster. Apparently plants get sunburn too.

UV is easy to filter; Ionizing radiation is more difficult.

RobertDyck · 2003-03-29 13:24:37

Teflon FEP is very UV resistant. In fact, it has been used for the exterior of satellites. UV resistance has been specifically studied for Teflon FEP for this very reason. I had tried to look for appropriate material for an inflated greenhouse. Tefzel film has higher tensile strength than Teflon FEP, slightly lower mass, and is more gas impermeable. Tefzel can withstand temperatures down to -100?C before it become brittle; fine for Mars tropical latitudes where temperature doesn't get below -80?C, but not the south pole where it can get down to -140?C. Teflon FEP can withstand temperatures down to -240?C. Tefzel can withstand UV outdoors in Florida without yellowing or otherwise exhibiting UV degradation. However, Penelope Boston reports that Tefzel cannot withstand the higher UV intensity of Utah; so Mars is right out. Teflon FEP, however, can withstand the UV of low Earth orbit. Dupont has tested Teflon FEP film outdoors in Florida for 20 years without any detectable degradation.

RobertDyck · 2003-03-29 23:03:40

Not good enough maybe. But Teflon FEP isn't transparent, right? We need something transparent....

According to the Dupont Teflon FEP web page, solar transmission is 96%. This is the most transparent film I know of.

tim_perdue · 2003-03-30 11:07:07

Have you guys looked at the results from "demron" - it looks like it would be quite effective in blocking cosmic rays, and it's a lightweight fabric:

http://www.radshield.com/Demron_Test_Results.pdf

sethmckiness · 2003-04-20 03:05:32

could we be trading one problem for another..? I thought I remember something about being next to Electromagnetic fields, and it leading to Cancer/tumors. don't quote me on it. But might we be fixing one problem with another. I know there is a proxmity issue but I may be completely off base.

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#1 2003-03-14 11:39:24

Re: Mars radiation a serious risk to astronauts. - Is radiation a surmountable problem?

#2 2003-03-14 14:05:54

Re: Mars radiation a serious risk to astronauts. - Is radiation a surmountable problem?

#3 2003-03-14 14:18:59

Re: Mars radiation a serious risk to astronauts. - Is radiation a surmountable problem?

#4 2003-03-14 17:12:49

Re: Mars radiation a serious risk to astronauts. - Is radiation a surmountable problem?

#5 2003-03-14 19:22:27

Re: Mars radiation a serious risk to astronauts. - Is radiation a surmountable problem?

#6 2003-03-14 21:19:32

Re: Mars radiation a serious risk to astronauts. - Is radiation a surmountable problem?

#7 2003-03-17 01:53:31

Re: Mars radiation a serious risk to astronauts. - Is radiation a surmountable problem?

#8 2003-03-26 13:53:07

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#9 2003-03-26 14:06:37

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#10 2003-03-26 14:55:33

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#11 2003-03-26 19:53:03

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#12 2003-03-28 11:24:03

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#13 2003-03-29 10:26:48

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#14 2003-03-29 11:31:59

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#15 2003-03-29 13:24:37

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#16 2003-03-29 23:03:40

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#17 2003-03-30 11:07:07

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