The US Radiation Worker annual radiation limit is 5 rem, or 50mSv/year. Divided into the 2000 annual working hours, that’s 0.025mSv/hour.
The Mars Curiosity rover measured an average dosage on Mars of 0.67mSv/day at about -4km altitude. That’s 0.028mSv/hour.
If you worked somewhere lower altitude, like Hellas Basin (-7km or even possibly -8km) or a place like Valles Marineris at -5km and valley walls nearby, you should be able to get that down to the 0.025mSv/hour of US Radiation Worker limits.
Or work French hours. 😉
Or limit it to 1000 hours per year like commercial airline pilots, the rest indoors.
So really, at least during solar max (when GCR is at a nadir), the surface radiation levels of Mars don’t seem like any insurmountable barrier at all, provided you can adequately shield everywhere else and provided you’re okay with US radiation worker limits. For instance, 3m of polyethylene at -5km altitude (Valles Marineris) gives you 22mSv/year (although the model I use for that calculation is questionable to me… it seems there are too many low-energy neutrons). 1m of water/PE is 48mSv/year. Of course, you can also bury below a bunch of regolith or burrow to achieve arbitrarily low radiation levels.
Long-term, I suspect we’ll find drugs that are effective. Or we’ll find out if the Linear no-threshold (LNT) model is correct or not. In any case, when there are millions of people on Mars, it’ll be much easier to produce high-quality data about relative risks for low-dose radiation and also easier to develop enough statistical power to show whether or not drugs like Amifostine can protect against low-dose chronic radiation as well as the acute radiation we know it’s effective for.
Chris Stelter
Latest posts by Chris Stelter (see all)
- How much mass can we put in orbit before running into atmospheric constraints? - July 19, 2020
- Adding an Earth-sized magnetic field to Mars - June 18, 2020
- A human tribe is a Von Neumann probe - May 24, 2020
There’s really no reason for humans living within martian habitats to be exposed to levels of radiation beyond 5 Rem per year, even during solar minimum conditions, as long as your habitat is shielded with at least 1.5 meters of regolith or approximately three meters of water.
And I seriously doubt that humans living permanently on the martian surface would spend more than 10% of their time per week (17 hours per week) in pressure suits, outside of the comfort of their protective habitats. During solar maximum and minimum conditions, that would only add about 0.8 to 3.3 Rem of extra radiation exposure annually.
And its still not clear if levels of radiation nearing 10 Rem per year is harmful to the human body.
Marcel
Cosmic Radiation and the New Frontier
http://newpapyrusmagazine.blogspot.com/2014/03/cosmic-radiation-and-new-frontier.html
In terms of NASA exploration, it seems most outdoors wandering around should be
using teleoperated robots. I don’t think one needs any rover with a cockpit for crew.
One could have robotic “pickup” that could carry humans in spacesuit as cargo. And if there some reason one had transport crew long distances via rover. One carry an inflatable tent which would allow crew to get out of their spacesuits. But I think long distance travel should done with hoppers or aircraft of some kind. So have robotic “aircraft” which can also carry crew as cargo.
In terms of NASA Mars exploration, one should consider the cost of human crew somewhere around the cost of $1 million per hour. Or don’t want crew wasting time driving or walking. So one use robots to do the traveling. If using robotic one also use slow travel such using balloons and one crew member could monitor 3 or 4 different robotic vehicles- doing various things. Or basically the crew have a lot of expensive robots which they manage and fix and troubleshoot in various ways. So one would need a workshop/garage which can repair anything.
I’m thinking in terms of at least 1000 people on Mars.
Can anyone give a reference to a graph, calculator, or formula that shows the reduction in radiation given different materials of varying thicknesses greater than 50 cm?
Good question, Doug. I’ve thought the same thing. I’ve been using oltaris.nasa.gov and calculating it myself. (You end up with a lot of low-energy neutrons, way more than might be reasonable physically, so either the calculation is incorrect or there may be a way to enhance the shielding at a certain point by using a neutron scavenger.)
It seems in terms of early human settlements, Martians should live in natural underground caves and underwater at the surface.
It seems digging underground is something the Martians should get good at.
Mars, unlike Earth is a place to dig. Earth is water planet and has water table which makes it hard to dig underground. Earth also has a thin crust with lava about 50 km under the surface. Mars may not have a global water table, and if it does it could tend to be deep. So 100 meter under Mars surface one could have liquid water, but average depth could be over 5 km. If deeper than 5 km then in that region one could dig over 5 km under the surface- something not very doable on Earth in most places.
Also one might be able to dig over 50 km under the surface on Mars [something not really possible on Earth]. One could dig below 50 km and one could have water table above it. On Mars it might be possible to deplete a regional water table of it’s water.
One might worry about the lack of water in Mars water table- or think of it as advantage to have a lack of water in the water table. One could use trillions of tons of water on Mars if you had it.
What you use billions of tons of water for is making lakes on Mars which people can live under. So shallow lakes which are less than 100 meter deep.
Mars has 0.379 the gravity as Earth has. Or 100 meters depth of water has same pressure as 37.9 meters of water has on Earth. Which 14.7 times 3.79 = 55.7 psig.
Human can swim with “single breath”:
“Francisco “Pipin” Ferreras broke his own world record for “no-limits” free diving today, October 13, 2003 , descending 170m into Los Cabos Bay in Mexico on just one breath of air.
The historic dive took about two minutes and 40 seconds and saw Ferreras plummet to record-depth using a weighted sled, then rocket back up to the surface when his air tanks inflated.
Decompression wasn’t needed because he didn’t breathe in any air during the dive.”
http://www.funtrivia.com/askft/Question43041.html
I didn’t realize they got to 170 meter, but comparatively 37.9 meters pressure or 100 meter under water on Mars is doable even without scuba. One could have “ski towline” to next door neighbors which are than 100 meter away, go there in one breath.
But light levels at around 100 meter would rather dim so might not want to be so far under water, but at the higher air pressure, one breath should last longer, so allow further travel with single breath. So the neighborhood transportation network could below the living areas. So go lower to your basement and at an increased air pressure- go thru 10 door with 1 psi higher- like Get Smart – to go next door.
At surface the water could frozen or a warm as 20 C- it boils at higher temperature.
Ironically, the problem on mars is that people may not get enough radiation to remain healthy. The human body needs radiation damage to keep its repair systems functioning.
In any case, it’s not a reason to keep from going.
“Or work French hours.”
So you’re a Jeb Bush fan? Well, that’s a curious way to display it, but hey, that’s your blog.
However, as someone actually working in France, I can tell you that this was a stupid, stupid comment. An an insulting one, actually.
Sorry, I didn’t mean to insult the French. I think a good case can be made for a reduced work week.
But maybe have a little sense of humor! I wouldn’t shy away from jokes like “SpaceX new rocket can launch 50 metric tons, or, to put it terms we can all understand, about 3 Americans.” 😉
“Can anyone give a reference to a graph, calculator, or formula that shows the reduction in radiation given different materials of varying thicknesses greater than 50 cm?”
The 2011 US Department of Energy study on cosmic radiation has tables and graphs showing the radiation shielding effectiveness of a variety of materials up to 100 centimeters (one meter):
http://www.pnnl.gov/main/publications/external/technical_reports/PNNL-20693.pdf
Sorry I may have over-reacted a bit.
The thing is, there are many things to mock about the French, for example strikes (to rip an example from the headlines), bloated administration and regulations, the unique inclination to screw the best ideas up, a rather picturesque political class (that one minister in charge of fighting tax avoidance was caught with 25M€ on a Swiss account 😀 ), an addiction to revolutions and uprisings, having an opinion on everything and as such complain about it (well, it does make for good engineers at least)…
The problem is, pretty much the only mockeries commonly found about the French are very wrong, and often with a dirty political origin, so they are offensive by design.
In this one case, weekly hours are, for many, actually too long. I’ve seen the health of friends degrade from it, so it hit a bit too close to home.
(Though this one is not as offensive as that *other* one)
That said, “or work French Public Service hours”…
about 3 Americans
Hey, I
resembleresent that remark!Well, actually, after losing 112 kg, not so much any more. My Russian Ex-wife takes more vacations each year than most Americans do. She’s heading to Crimea in a few days.
“For the moment, I’ll ignore these non-trivial “arrival†issues and
focus instead on the two remaining objectives – “survive and thrive.â€
Only rudimentary attention has been given to how humans will survive
on the martian surface. Certainly, additional problems will come up
that we cannot know now, but the ones we do understand are formidable
enough. In contrast to the press it receives, the martian surface is a
cold, alien, hostile environment – much more dangerous than free space
or even, in some respects, the lunar surface.”
http://www.spudislunarresources.com/blog/delusions-of-a-mars-colonist/
Paul Spudis is making argument against going to Mars before the Moon and saying
Mars over-hyped about Mars being like Earth. And basically that Mars is not viable
for human settlement- which I disagree.
I think one characterize Mars as cold and dry, but for humans Mars could have vast amount of available water, and I would say that living on Mars is not colder than living in Canada.
I think adding atmosphere to Mars would be a wrong thing to do, and though adding
atmosphere to Mars would make the planet Mars a bit warmer, it would make it colder for humans to live on Mars.
The lunar poles are coldest place, this side of Pluto, but for human in spacesuit, it’s not cold- rather a more important aspect is it’s dark- you would need a flashlight or something. The reason the coldest place is not cold for humans is because we know how to insulate and because human create heat. Humans can operate in say -80 C conditions in the Antarctic- that is cold for humans unlike the lunar poles. But what will kill a human pretty fast is swimming in 5 C water- without a wet or dry suit [or without insulation- polar bears are quite happy in 5 C water]. And spacesuit is needed for the Moon and Mars and it’s better insulated in a near vacuum, but a spacesuit would be fairly useless to kept warm in -80 C conditions in the Antarctic- though it acts sort of like a dry suit in 5 C water.
So the vacuum of Moon and near vacuum of Mars keeps human warm in a spacesuit- without spacesuit, you are dead- because you can’t breath.
An advantage of Mars near vacuum atmosphere is it allows liquid water to exist on the Mars surface. On the Moon liquid water boils and turns into ice and will evaporate as ice into it’s colder than -100 C. Mars one can have liquid water somewhere close to 20 C [or room temperature]. The water does evaporate, but water evaporate on Earth.
I would think that there conditions on Earth where 20 C water could evaporate quicker as compared to Mars.
So one could make a lake on Mars. And humans could live within the lake, and have enough water pressure to allow humans to breath. One could scuba dive on Mars in a lake- but you can’t come to the surface or you can’t breath.
So one build houses under the surface of the lake and hold your breath and swim from house to house. Unless one adds dome on the Moon to create mars like pressure you can’t do this on the Moon.
So building lake requires a fair amount to water and one needs the water to be cheap per ton of water. Water quality doesn’t matter much. If swimming around in swimsuit or the nude, one would prefer clean water, though saltwater not much of a problem.
I’ve heard the opposite argument being made, i.e. that without some sort of active cooling system (like a sublimator used on Apollo, etc), even the cold Martian air wouldn’t keep a suited astronaut cool.
I find Paul Spudis to be remarkably dishonest in his arguments. For instance, the Mars surface is much more dangerous than free space?? The Martian atmosphere at any places humans are likely to inhabit (lower altitude places like most of the northern hemisphere plus Hellas Basin and Valles Marineris) shields you from ALL micrometeroids and reduces ALL recorded solar flares to non-life-threatening levels. This can be easily shown. That’s 2 significant threats that you don’t even have to think about on Mars. The ability to dump heat into the atmosphere makes thermal control easier, in fact, and the atmosphere is still thin enough to prevent massive heat loss (again, some have argued you’d still overheat without a sublimator or “sweating”).
Paul Spudis likes the Moon. That’s great! But he shouldn’t spread FUD in a flailing attempt to get more people interested in the Moon. If he just talks about his lies about Mars being so bad, then most people will take that as, on the whole, reason to not be interested in human spaceflight in general. Talk up the Moon, please, but don’t tear down everything else.
The extra cooling argument is made even weaker if you consider that at least partial counter pressure suits could be used. Counter pressure suit can be made breathable. This means that it will allow the person wearing it to sweat to moderate their body temperature. The result is that it is very possible suits in the future will not need cooling unit or will only need very small “climate control” units.
Right. If you sweat directly or indirectly (i.e. put an evaporator on your suit), the extra cooling argument isn’t a show stopper even if it’s true.
How does Spudis think that lying benefits his case (he’s much too smart to make these kind of mistakes.)
“For instance, the Mars surface is much more dangerous than free space?? The Martian atmosphere at any places humans are likely to inhabit (lower altitude places like most of the northern hemisphere plus Hellas Basin and Valles Marineris) shields you from ALL micrometeroids and reduces ALL recorded solar flares to non-life-threatening levels.”
Where is safer to be outside in spacesuit- LEO, Lunar, or Mars surface?
With the human made space debris, it seems LEO would most dangerous.
It seems that during comet showers, Mars would be safest place.
Hmm, on Earth one watches meteor shower during the night, but shouldn’t there be more during the daytime [though one can’t see them- oh, though I guess one is seeing the dust trail path of incoming comet]. It should noted that Mars get about twice impactors as Earth, though average velocity is less. And solar flares would safer on Mars surface- they are a bit weaker at that distance and the mars atmosphere blocks a lot of the effect. The main thing dangerous of Mars is the distance to medical treatment- remedied by bringing all kinds of medical treatment to Mars- but probably don’t need flu shots:) Though the low gee environment could cause variety of unpredictable problems- and artificial gravity could considered as possible medical treatment. Though also seems possible lower gravity could a medical treatment for something. As general note it seems the microbial life, the humans bring to Mars may react in ways not predictable.
So generally it seems to me the main danger of Mars is getting to Mars rather being on Mars. And that is a reason to get to Mars fast, rather than 6-7 months.
It’s interesting though about free space near Mars in terms of micrometeroids- I hadn’t given that much thought. I generally think one should stage in High orbits of Earth and Mars, but not sure of relative risks of micrometeroids.
In terms of stuff of Earth or Mars planetary system, it’s quite safe [or safest], but what about solar system stuff- asteriods/comets stuff. As general rule it should be safer the GEO in terms of Earth. Or at the geostationary distance of Mars.
Does Mars low orbit have risk from larger impactors’ ejecta and what smaller stuff hitting Mars moon and entering Mars orbit?
So with Earth we get car size rocks hitting Earth on monthly basis- and I guess, this doesn’t effect LEO in terms of orbital debris. But with Mars these same size impactor
hit the surface- at say 10 to 15 km/sec, which would put stuff into orbit and into escape. It would seems that chunks rather small pebbles would get back out of Mars atmosphere, unless one getting plume of gases carrying small bits out into space.
Which kind of gets to question what does nuclear explosion at surface look like on Mars
or simply a large chemical explosion.
So we or I know that 1/2 km diameter impactor on Earth will make the plume I am talking about- so something equal to 1/2 million Megatons. Or nuclear bombs dropped on Japan are not powerful enough, nor would even Tsar nuclear bomb would do it on Earth, but I would guess that something between the atom bomb and Tsar bomba hydrogen bomb might do it on Mars.
And if talking about Mars moons, it seem a stick of dynamite would do it [though of course they have no atmosphere]
As far as Spudis, “lying” may be too strong of a word. Intellectually dishonest hyperbole is maybe better.
Spudis is Zubrin but for the Moon. He’s passionate, even angry about the lack of progress, and focused on a singular goal. That can lead to bias.
Dr. Spudis doesn’t allow much time for comments.
“Suppose the govt. (any govt.) did something wise for a change and declared they would fully acknowledge title to martian property (144 million sq. km. of land.) Suppose speculators bought that land for a penny a sq. km. Would that be a smart decision?”
Nah. How about each setter gets a small amount of land which can never be taxed, and larger chunk of land which can be taxed. As all taxes do, one starts with small tax- easily less than 1% of it’s value, and could start a tradition or hope that no residential urban area ever have higher tax than 1%. So small amount of land may be 1 square km and large amount of land maybe 100 square km. And both amounts lessen with each new settler, so that by 100,000th new settler, it’s down to 1 acre tax free and up 1 square km free but has some taxation. So settler would take the tax free land and could decide to take max amount of land given but has yearly tax which is more the larger chunk of land you accept. And of course one can sell any land you receive for free. And of course one allot some land for parks and governmental use [if governmental use will occur within couple decades]. Of course Government will own all land which is given to any new settlers- and probably zone them- if it makes any sense. The tax free land can’t zoned- or zoning can seen at governmental burden or tax. One might limit the tax free land, such as only extend 5 km underground and 5 km above the ground- or be even more limited in terms the airspace and underground. Part of governmental park land might regions that persons can with government permit, drop space rocks into- assuming with the right of mining whatever remains of space rock which impact within the region.
Anyhow giving free land is to way encourage settler [and essentially pay them for arriving on Mars {alive}]. One assume if land on particular spot and available, one could claim by landing on it, or if landing in some town, you do whatever paperwork and select any region on Mars- or maybe towns have limited area of planet, so one have land in town near where you want the free land.
I think land speculation should require some work to be done. So if town is settled, that is work done- so people [government] of a town could sell land to Earthlings, and as could anyone going Mars getting free land, could sell that land to Earthlings.
Or land ownership is right to exclude other people to use that land- and don’t see why Earthling should able to stop people from going to Mars. And since they aren’t on Mars, they would assigning Martians with job of enforcing the law- make Martian do work of such enforcement [which Martian have little interest in doing- other than it’s a bad law which “should be” enforced]. Or encourages not respecting laws- or encourages lawlessness in general.
Anyways, I think Martian will export foodstuff and timber stuff, not to Earth surface but to the Earth system and other places in solar system which humans want.
If you mine water on the Moon, it opens the rest of solar system. But if no one mine lunar water and opens the solar system, Mars settlements will also open the rest of solar system. Or one argue that Mars is not best gateway to rest of solar system, but if only Mars has human activity [has human settlement] then Mars would be the only gateway to solar system. Same applies if no one goes to Moon or Mars, but establishes a L-5 colony- it then become the gateway rest of solar system.
You are not going to have over 1000 people living on Mars and not have asteroid mining and lunar mining, and other stuff. Or it seems fairly obvious to me, that one takes asteroid material to Mars if there people living on Mars- unless Martians have silly laws against it [and enforce the laws]. Earth will probably have laws against it, and if Martian aren’t crazy, they should have less laws which restrictive as compared to Earth. And if no one is on the Moon doing stuff, and there are thousands of people on Mars surface, and asteroids can be brought to Mars, it than seems the first “L-5 colony” would a Mars L-1 or 2 colony. And provide some jobs to people living on Mars surface of doing tele-operational work.
gbaikie, Mars currently has no government. What government would have jurisdiction over the settlement and be collecting property taxes?
It seems to me one of best reason to settle Mars is to start a Martian government.
And if one actually serious in going there in less than 5 years, to start a settlement I would think you would begin to start a Mars government before you have arrived on Mars. Part of starting a government is to be recognized as the Mars government by existing Earth governments.
Now, Morocco was first nation to recognize the US, so it seems like it might be good idea to see if Morocco wants to be first nation to recognize the Mars government.
Not sure something like Mars One would count as a settlement for this purpose- or could seen as effort to start a colony rather having a colony- or it might seem more like a stunt. But if one going to get say 50 people there within a few years and had say a dozen there already, and other things seemed reasonable, I think various Earth governments would be quite tempted to recognize this new nation. Though one really don’t need this recognition- it’s sort of like presidential endorsement- it helps a bit and it depends on which nations do it, though it might take decades for all nations to recognize the Mars government.
gbaikie, whether they call it a government or not a group of colonists would in fact be a government. That’s a separate issue from many others. A mars government doesn’t need to collect taxes. That’s just setting a bad precedent because we know what happens after that. Mars doesn’t need to raise an army for defense because nobody today cares. Any other government service can be done better privately.
You need contract and tort law and that’s about it.
gbalkie,
“An advantage of Mars near vacuum atmosphere is it allows liquid water to exist on the Mars surface.”
Where did you get this idea? Mars’ atmospheric pressure is below the triple-point of water. Water can only exist as ice or gas, depending on temperature. Liquid water will boil and/or freeze.
“Mars one can have liquid water somewhere close to 20 C [or room temperature].
[…]
I would think that there conditions on Earth where 20 C water could evaporate quicker as compared to Mars.”
These two lines are just nuts. Even at the deepest spot at the bottom of the Hellas Planitia the air pressure is only 1kpa. At 20°C, that’s less than half the required pressure for liquid water.
Re: Paul451 says July 9, 2016 at 2:36 pm:
–The air pressure is so low on Mars that even in the most favorable
spots, where the pressure is higher than average, liquid water is
restricted to the range 0 to +10 °C,” says Bob Haberle of the
NASA/Ames Research Center. “Fresh water on Mars begins to boil at 10 °C.–
http://science.nasa.gov/science-news/science-at-nasa/2000/ast29jun_1m/
–Martian atmospheric pressure averages about 600 Pascals, which is just
below the lowest pressure where liquid water can exist, called the triple point.
Put another way, this means that below this pressure there is a direct transition
between solid and gaseous states, like what you observe with dry ice
(solid and gaseous carbon dioxide) on earth.
So let’s assume we have a bottle of liquid water at room temperature, which is about
300 Kelvin. Let’s also assume we’re on Mars. What happens when we take the lid off and pour it out? According to our phase diagram, it should rapidly boil and form vapor.
If you’re wondering where this is on the diagram, it’s just above the first ‘o’ in
“Solid/Liquid/Vapour triple point.â€
I don’t want anyone to assume this means that liquid water can’t exist anywhere on Mars.
I just mean to say that water at room temperature is too hot to be liquid. In fact,
when I told you that atmospheric pressure at the surface is 600 Pascals, I lied a bit.
That 600 Pascals is the average surface air pressure – the topography has highs and
lows where the pressure will vary and since Mars doesn’t have seas it makes it difficult to define sea level. In fact, prior to 2001 the zero elevation was defined as the height where ambient pressure is 610.5 Pascals, which is where liquid water could exist.
And even though lows get as cold as −140 °C (−220 °F) , surface temperature can reach highs of 35 °C (95 °F) in the summer. This means that any elevation below “Martian sea level†with the right conditions could potentially host liquid water in the warm Martian summer.–
http://quarksandcoffee.com/index.php/2015/09/28/would-poured-water-boil-or-freeze-on-mars/
Note: last reference has phase diagram.
And 300 K = 26.85 C = 80 F
I agree 26 C water in a open bottle could boil on Mars.
At .5 psi 3.45 kPa [34.5 mbars or 3450 pascals] it boils at 26.4 C
http://www.engineeringtoolbox.com/boiling-point-water-d_926.html
Which fits the the phase diagram.
Follow 300 K line up and across between 3rd and 4th line above 1 kPa.
And at 1 kPa it’s around 280 K [6.85 C]. 1100 pascal is about 290 K [16.85 C]
— Models and data from previous missions had predicted that Curiosity would land when pressures were around their lowest. The rover’s measurements have borne this out, rising from a daily average of around 730 pascals during Curiosity’s first three weeks on Mars to about 750 pascals more recently, researchers said.
“The pressure data show a very significant daily variation of pressure, following a
fairly consistent cycle from sol-to-sol,” said REMS principal investigator Javier
Gómez-Elvira. “The minimum is near 685 pascals and the maximum near 780 pascals.”–
http://www.space.com/17828-mars-weather-curiosity-rover-discovery.html
Here water could normally be liquid.
wiki: “The altitude difference between the rim and the bottom is 9,000 m (30,000 ft).
The depth of the crater (7,152 m (23,465 ft) ( 7,000 m (23,000 ft)) below the
standard topographic datum of Mars) explains the atmospheric pressure at the bottom: 12.4 mbar (0.012 bar) during the northern summer”
https://en.wikipedia.org/wiki/Hellas_Planitia
Here water would always be liquid and could be 20 C [68 F].
The sunlight near summertime could during day warm water to 20 C.
Keeping it above 10 C during the wintertime by sunlight during the day could a problem.
Solutions could be to augment heating from sunlight with solar thermal panels or using Nuclear waste heat.