Radiation Sickness, Cellular Damage and Increased Cancer Risk for Long-term Missions to Mars
Written by Ian O'Neill
There is a nagging problem under the surface of the excitement surrounding the future of long-term missions into space. Human exposure to the high amounts of solar radiation and other sources of cosmic rays is likely to be the main factor that could curtail mankind's dreams for future manned settlements on other planets. The effects of radiation exposure to astronauts is not fully understood, but could range from acute radiation sickness (perhaps after being caught in an intense solar storm during interplanetary transit) to gradual cellular damage, greatly increasing the risk of cancer in long-term missions. So what can we do about it? Mankind is highly adaptive and some countermeasures are gradually being realized. (And yes, the Russian Space Monkeys might be able to help…)
The problem comes when humans leave the protective blanket of the Earth's magnetic field. Acting like a huge, invisible force field, the magnetosphere deflects most of the harmful high energy particles being fired from the Sun. Anything that penetrates this barrier is quickly absorbed by our thick atmosphere. Even at high altitudes, in low Earth orbit, some protection to astronauts can be provided (although the ambient radiation is far higher up there than down here). So when we talk about colonizing other planets and sending astronauts further and further into deep space, radiation exposure becomes a bigger risk.
An immediate concern is that astronauts may get caught in a solar storm, where the Sun (usually around solar maximum) ejects huge clouds of highly energetic protons. If the storm is intense enough, huge doses of radiation could be inflicted on the men and women in space. Roughly, a dose of 500 rads or more will kill a human in two to three hours, and a smaller dose could cause acute radiation sickness. Radiation sickness could be fatal in weeks should the astronaut not receive urgent medical care. How about the long-term, gradual impact of prolonged exposure to higher-than-normal doses of radiation? This is an area of space medicine that we do not completely understand as yet.
In new research by the Lombardi Comprehensive Cancer Center at Georgetown University Medical Center, the high-energy nature of radiation in space may lead to premature aging and prolonged oxidative stress in cells. This also suggests that astronauts risk a higher than normal risk of cancers, such as colon cancer, through exposure to "high linear energy transfer" (LET) radiation. LET radiation consists of the high energy protons emitted by the Sun and cause a huge amount of damage to small areas of tissue.
"Radiation exposure, either intentional or accidental, is inevitable during our lifetimes, but with plans for a mission to Mars, we need to understand more about the nature of radiation in space. There is currently no conclusive information for estimating the risk that astronauts may experience." - Kamal Datta, M.D., assistant professor at Lombardi and lead author.
With NASA's Project Constellation on the horizon, there has been a focus on the long-term effects of interplanetary radiation. Ultimately, this project aims to send humans to the Moon and Mars, but there are strong indicators that astronauts will face in increased cancer risk and lifespan reduction, a massive hindrance to a mission spanning several months or a thriving proto-settlement.
This is where the lab mice help us out. The amount of "free radicals" (highly reactive molecules often linked with cancer and cell aging) were measured and found that the mice developed highly oxidative (i.e. full of free radical molecules) gastrointestinal tracts when exposed to space-like high-LET radiation. The Lombardi group concluded that the mice had developed a high risk to various cancers, particularly gastrointestinal cancers. They also noticed that after exposure (even after two months), the mice prematurely aged, signifying that the effect of radiation damage can persist long after exposure to a high-LET environment.
So what can we do? There are several plans in motion to further test the effects of radiation on humans and to predict when astronauts will be at risk. This week, Russia announced (controversial) plans to send monkeys back into space, possibly as far as Mars. Once the shock of this "outdated" proposal wore off (the previous Russian space monkey program ran out of funding in the 1990's), it became very clear as to what the Russian space agency is hoping to achieve: to have a better understanding of the long-term exposure to a high-LET environment on the human physiology. Many will argue that this practice is cruel and unnecessary, but others will say monkeys are used in experiments every day, why shouldn't they help us in the ultra-modern world of space travel? The jury is still out on this debate, but there are many ways to investigate and counteract the radiation effect on humans.
There are also many systems in place to protect mankind from the onslaught of solar storms. Using the Solar and Heliospheric Observatory (SOHO) and other craft located between the Earth and Sun, an early warning system has been set up to provide astronauts on orbit with some time to take cover should a solar flare be launched Earth-bound. This system is fully operational and has already proven itself. Recently, I toyed with the idea of a similar Mars-based early warning system, providing future Mars colonies with about 40 minutes advanced notice of an incoming solar storm.
Shielding is another obvious protective measure. Lunar and Mars colonies are most likely going to use large amounts of regolith to block the incoming particles. Only a few meters of locally dug-up regolith will provide excellent protection. But what about the journey to Mars? How will the astronauts of projects such as Constellation be protected? Perhaps an advanced "Ion Shield" might work?
Whatever the effect of radiation on humans in space, it seems obvious that we are in the infancy of space flight and we are already addressing some of the most difficult problems. Over the next few years, much effort will be focused on the health of astronauts, hopefully finding some answers to the space radiation problem.
Original source: Georgetown University Medical Center
Filed under: Space Flight
April 16th, 2008 at 9:06 am
Forget sending Monkeys to Mars. Send humans from the get go. It is so politically unacceptable to put humans life in danger in such a high profile venture, but it wasts money and time unnecessarily. Going to mars isn't supposed to be a walk in the park, and this venture, as in all of the great exploratory movements of the past, will turn up plenty of qualified people willing to risk a 10-20% increased risk of Cancer.
April 16th, 2008 at 10:33 am
Very interesting.But wait humans already went to the Moon…. or THEY DID NOT.
April 16th, 2008 at 10:45 am
If you try and stop high energy protons with conventional shielding, you risk creating a shower of other more strongly ionizing particles and making things worse. The ion shield might be a solution. However, a simpler solution might be to have a plastic low-Z shield on the sun side of the living quarters. The protons would be coming from the sun. Compton scattering would send them off in some other direction. The sun only subtends half a degree, so we would have to make the thing about 1 cm larger for every 1 m it is behind the living quarters. Make it 1 m larger and stick it 100 on the sun side of the living quarters, and the only radiation that got through would be the stuff that was not deflected by more than half a degree or so. Anything that got through would either be a very lucky bit of highly ionizing radiation, in which case it would be rare, or a bit of weam,ly ionizing radiation, in which case it ought not to be too dangerous. In case of a solar storm, the shield could be moved even further back, and the passengers could sit down the centerline of the living quarters.
It is not a new suggestion. There are lots of types of shielding that we might use. Clearly shielding of any sort takes extra mass, and how much shielding we use will probably be a trade off between protection and weight. This suggests we will need to accurately know the health risks of combined sorts of radiation before we can design a Mars craft, hence the research.
April 16th, 2008 at 11:47 am
We certainly have to fully solve this problem before space travel beyond Earth's orbit becomes commonplace. Until then, as a previous commenter says, there will be a level of risk that is acceptable to the astronauts and the taxpaying public. If offered the chance to be one of the first people on Mars at the possible cost of five years of life-expectancy (ignoring the danger of not coming back at all) then I would be willing to bet that the vast majority of the qualified people would jump at the chance.
April 16th, 2008 at 11:55 am
Case studys have already shown an extra 1% increase in radiation exposure as to what we get on earth by going to Mars. (see Case For Mars, By R. Zubrin)
This radiation 'problem' is just more time wasting nonsense.
In terms of risk, anyone going there would gladly accept any risk, for example in everyday life, I accept the risk when I cross a street that a car may hit me.
But that does not stop me crossing the street, why should the risk of radiation stop us going to Mars?
Its about time mankind and their repective goverments 'grow a pair' and go to Mars.
April 16th, 2008 at 12:22 pm
That is very interesting what you mention about the 1% radiation exposure. I am very dubious whether this is totally correct, I'll have to check it out though. I read the Case For Mars a while ago, so I'll have to hit the books
I'm 100% with you on your opinion that we should just get to Mars and stop worrying about it. My biggest fear is that we are going to sit on it, procrastinate, get bogged down in health and safety regulations, then the US government changes policy and it's another 40 years till we consider a manned moon mission again. We've been waiting too long, and our technology is more than capable to deal with these problems.
Putting the radiation risk to one side, I have more concern for the psychological problems facing us humans after many months in space.
Thanks for the discussion, you got me thinking!
Cheers, Ian
April 16th, 2008 at 12:42 pm
I don't think i is exactly 1%, had heard it was at least that and possibly .5% higher in some quotes. However, I don't think the increased cancer rate is a big deal given the ever increasing rates of it here on earth. The biggest problem is the lack of treatment available to them.
April 16th, 2008 at 12:48 pm
Ian
April 16th, 2008 at 1:21 pm
"I have more concern for the psychological problems facing us humans after many months in space."
In answer to that one Ian, man has endured worst.
Zubrin probably said this also in one of his papers or books.
It took half a year to sail to Australia from Europe when Europeans where settling there, and in worst conditions than in a space craft, thats about the time it would take to get to Mars presently.
Also many people have survived wars without seeing home for years and not even spoke to loved ones and receiving nothing but terrible conditions as well as the enemy looking to kill you.
At least on the way to Mars they can comunicate with home, the apollo astronauts where never alone, even Michael Collins said he never felt 'alone' when he was in the command module by himself.
People are survivors, going to Mars is going to be easy on us compared to a lot of the stuff we have done before.
Cheers Ian
April 16th, 2008 at 3:26 pm
whatever
April 16th, 2008 at 3:32 pm
I'm with cheech on this one.
100% opposed to manned (or monkey) space flight.
April 16th, 2008 at 4:41 pm
Opponents to manned space flight underestimate the "imagination factor." Photos sent from the lunar surface captured the attention and imagination of nearly two generations. Similar phenomena happened when colonists sent back reports about a "New World." We need a spark to provide a long term commitment of resources and agenda to space exploration. I don't think there would be any shortage of people willing to subject their bodies to radiation in exchange to the among the first to set foot on new soil…
April 16th, 2008 at 5:06 pm
OK, I get the thrill, I get the imagination factor, I get all the politics behind such an undertaking (if the kind of politics pushing it is the right one, at least), I get all that, but I still think it's early to seriously think about putting humans on Mars.
We need a lot more experience in Earth orbit first, we need to have a presence in space that is quite a bit more routinary than the one we have now, we need to perfect the techniques to build and repair in micro and low gravity, which means we may need a moon base before we go to Mars. AND we need to explore the planet a whole lot better. Why not build a whole flotilla of rovers similar to the highly successeful Spirit and Opportunity and set them to peek around the planet for quite a while longer? Why do it with people relatively soon, when the robots are able to do a lot of work for a fraction of the cost?
Whenever I hear of manned spaceflight beyond low Earth orbit, I get the shivers at the thought of the huge amount of breathtaking science that may get put in the drawer due to the sheer cost of sending people to the Moon or beyond.
'Cause yes, robots can also stir mankind's imagination. Hubble has been a continuous source of awe, and so has been Cassini and the various Mars robots. The same could have happened with Venus Express, if only its object of study showed us a prettier face and ESA had better PR skills. And I can't wait to hear from Dawn and the Pluto part of New Horizons mission. And even Rosetta, not to mention Messenger.
If a manned Mars mission implies cuts in robotic missions, and I really can't see how it can not imply, then I just don't want to see it. We'd be losing way too much in exchange for a bit of thrill and sense of adventure. I just don't think it pays.
April 16th, 2008 at 5:25 pm
I believe your numbers are off, 5000 rad will be lethal in hours. 500 rads, rapidly delivered, is fatal to some of the population but only after a long course of radiation sickness.
April 16th, 2008 at 9:46 pm
I expect, in the next decades, we'll go to Mars on a 6 month ballistic trajectory just to do it. It will be on the razor's edge of our technology, much like Apollo, and we may or may not get there and return much like the engineering gamble that was Apollo. While Apollo only had to keep all the technology running perfectly for 2 weeks or so, a mission to Mars is an engineering nightmare because we're looking at 2 years of perfection for a Mars mission. One hiccup and it could be all over. Apollo 13 illustrated all to well how close to failure each mission to the moon actually was.
More than radiation (though not to minimize it in the least) the constant threat to the human body is 6 months of weightlessness. We can shield ourselves from the solar flares that may or may not occur on a mission but astronauts will always suffer from the weightlessness problem.
As it stands now, astronauts and cosmonauts that return from 6 month stints on ISS are, for all intents and purposes, basket cases physically. Every effort to stave off the effects of weightlessness really doesn't ameliorate the debilitation they endure. What will happen when a basket-case astronaut lands on the surface of Mars, experiencing his/her first gravity in 6 months, and there's a life threatening issue that must be dealt with immediately? It's likely there would be a mission failure because the infirm astronaut is incapable of physical interaction rather than the insolubility of the threatening issue. More than anything else, I believe this is the potential showstopper for a mission to Mars.
That said, I don't think we're forever doomed in any attempt to get to the Red Planet. I think our propulsion technology needs to be upgraded and when we do that we'll go to Mars on a regular schedule not unlike our pioneering expeditions to the moon during Apollo.
Chemical rockets giving a Mars ship a huge kick at the outset of a mission and then freefalling on a ballistic trajectory is the problem. A mission to the moon taking 3 days is easy. Make it a 6 month voyage and we're into an entirely differerent technological area. I believe the solution lies in the development of an ion drive or a variant. The operative fact here being that the drive be sufficiently powerful to accelerate a mission-viable mass at 32 feet per second squared or 1 g.
I had the opportunity to speak to the Principle Investigator for the Dawn mission to Ceres and Vesta currently enroute to these minor planets. Dawn is using 3 ion drives that, admittedly, are very low power but their potential for the future is the fact that they run constantly and, though acceleration is very slow, it is indeed accelerating to its objective. I asked the PI if these engines could be scaled up and he assured me they could. I think an advanced ion drive, several generations removed from these drives and capable of accelerating a mission-viable mass at 1 g thrust will put the human race on Mars for the remainder of our existence. These drives will make us a spacefaring species.
Consider the mission scenario: leaving Earth orbit the engines are powered to 1 g acceleration. All occupants feel normal Earth weight and function as they would if they were, say, on a submarine. At the half way point, the vehicle is turned around and for the remainder of the flight, until orbital insertion around Mars, use the engines to decelerate. The occupants still experience a normal 1 g environment.
I have read speculative papers that say such a ship could be at Mars in 2-3 weeks. If these numbers are valid, the benefits are manifold. Gone are the tribulations of 6 months of weightlessness. The psychological effects of being cooped up in a 'tin can' are minimized. The long term exposure to the radiological environment of trans-Martian space is significantly reduced. And, as the engines get more powerful, the spacecraft habitat can become more protective by installing lead shielding. The efficiencies of these engines should reach a level where mass will be a minor consideration.
I believe that research and development money should be focused on these engines. I believe once these engines are fielded and operational we'll have a thriving Mars colony with supply and crew rotation ships arriving on a regular schedule similar to our outposts at Antarctica. I hope I live to see that day.
April 16th, 2008 at 11:33 pm
Having approached the report from the National Academy in Washington with skepticism, after finishing their latest report, I've concluded it is not, as I'd believed, simply JPL budgetary propaganda.
The Academy spelled out knowledge gaps, for example, and was more than useful and certainly a scholarly and serious work.
Among their many conclusions is that we do not yet have sufficient shielding from Galactic Cosmic Rays, particularly from the heaviest and most energetic nucleons,
Lunar travel, the Board concluded also, fell well within the 3 percent probablity of REID (Radiation Exposure Induced Death) but all estimates of missions to Mars fell outside this minimum probability that stands as a proven standard for NASA safety protocols, particularly for what can be described as non-linear probabilities, basically a flip of the coin.
Sorry, Hoaxers, but your average trip through the Van Allen Belts is not a proven hazard and sufficient mitigation exists for LEO and short-term lunar distance flights, though obviously Solar Partical Events pose great risks.
And NASA's basic science into radiation is dependent on a Air Force facility that may soon close down.
Far from the Government Accounting Offices screed, MANAGING SPACE RADIATION RISK IN THE NEW ERA OF SPACE EXPLORATION, from the National Research Council of the National Academies, is available in pre-publication at their website.
Facinating reading for anyone wondering where to find their niche in the future of manned (and unmanned) exploration. Discover an effective method for sheilding, or, better, mitigating GCR exposure, heaviest at Solar Minima, like the one underway now. The world may beat a path to your door. Just remember there are all kinds of radiation, some more head-scratching than others.
Such technology would make life on Earth a higher probability, as well. The Solar Minimum underway at present (accompanied by an unusually strong solar wind) means GCRs are infalling at 50-60 percent higher a rate than at Solar Max.
April 17th, 2008 at 1:28 am
If humans didn't go and explore themselves most of the people leaving comments here would be doing so from Europe and not from America.
We'd still be in the dark ages huddled together in dark box.
Its in our nature to explore and to do it ourselves.
April 17th, 2008 at 2:15 am
ok . sooo
moon mission is all fake
oh…you bastard , ian !!!
April 17th, 2008 at 5:27 am
The answer will probably be a radically adapted outer skin of carbon fiber, just as a stealth plane uses. The internal sandwiching construction actually refracts/radiates the probe impulse around the craft to see the empty sky on the other side.
April 17th, 2008 at 5:48 am
Does it annoy anyone else as much as me ,that after almost 50 years of manned space flight and about one quarter of a trillion bucks spent on the shuttle and the ISS that we are asking questions like this now.For the the last 35 years we have done no more than Gagarin did.gone nowhere and learned very little about real space flight.Had the airplane been managed this way we would still be taking 10 minute flights in biplanes built of cloth,wood and wire.
Finally we are moving forward,but many of us seem to be so fearful.There are risks out there and some will die.That is always the reality of going into the unknown.
April 17th, 2008 at 5:51 am
Why not create a magnetic field around the crew quarters? If the field is strong enough and large enough, would it not also act as sheilding?
April 17th, 2008 at 8:46 am
I think somebody spoke too soon. See, e.g., http://www.sciam.com/article.cfm?id=new-drug-protects-against-radiation-damage
April 18th, 2008 at 10:42 am
I was thinking the same thing. Set up a magnetic field around the craft and habitat.
Btw.. Our priority should be propulsion. Speed! I am getting so tired of hearing “six months there, a year on the ground, etc..” A lot of our “short-term” goals would be a heck of a lot easier if we could go faster. NASA should offer an “X-Prize” with a substantial payoff or lucrative contract to anyone who can build a (practical) working system that can propel humans and cargo in space to at least 10 times faster than we can now. If we put more focus and resources into faster means of travel, we could end up accomplishing a lot more, a lot faster… I wish I was smart enough to figure it out…
April 18th, 2008 at 10:45 am
By the way…….., nobody seems to have caught (or read) my DHMO rant on April Fools… I'm so disappointed..
April 19th, 2008 at 6:58 am
For Al…
We can go to Mars faster than 6 months.
It just takes more Delta V.
Which means bigger rockets, more fuel, etc. etc. and then we have a 'Battlestar Galatica' type ship that costs so much that no one will pay for it.
The reason for 6 months is because its cost effective, using a near Hohmann transfer from Earth to Mars, we use far less delta V.
Lets get to Mars first and set up a small colony before we have to worry about shorter trip times, after all humans didn't wait for speedy transatlantic flights before traveling to North America.
April 20th, 2008 at 2:22 pm
Steven,
Good to get a reply……..
…….
What you wrote was my point. The mentality of us today. Build a gigantic ship, or an umbrella 50 km in diameter, or ion drives, or whatever…. That's my point. I used the word “practical”. In our lifetime.
By all means I am for space exploration -more than most, I'm sure- and we make due with what we have at the time. I'm just saying that speed is the key. We won't accomplish much until we solve it. And I'm not talking about folding space or going through worm holes or any other such things.
But hey, who am I? I'm a rebel. I still firmly believe that some day we will be able to build a machine that can propel us faster than 360 M m/s without traveling in time. It is really a shame we have slowed down so much that I'm going to miss it…
As for our (my) ancestors pulling up stakes and heading for the 'New World' two hundred years ago; I follow you. I may have never existed if they didn't have that adventurous 'spark' in them. I'm just getting impatient, that's all.
April 22nd, 2008 at 1:57 pm
Keep spreading the word, its about the only thing people like us can do.
Or we can make 3 or 4 billion and go there ourselves
I'm as impatient as you Al.
May 7th, 2008 at 4:37 am
Radiation, UV, X ray, effect of Weightlesness,
Absolute Cold temperature, Psycological factors of long time in space, high probability of being hit by space debris/ asteroids, unimaginable long distances between stars etc. etc. These are just a few known Hazards of space travel.
How can Humans in their right mind think of sending manned space crafts out of our Solar System. Why is NASA spending Trillions of dollars on developement of space stations and space crafts?
If the vision is to target space tourism and commercial ventures within our Solar System, maybe it makes sense.
But if the Human species would like to find a new home, before we run out of options on our present home, we better think out of the box.
The Human body is too fragile for space travel. We have to find some other revolutionary way forward if we want to save the Human species from extinction.
How about NASA inviting suggestions and proposals for a practicable and feasable alterantive to space travel on the lines of X-prize. I am sure there are some Humans on Earth who are capable of thinking far ahead than how to overcome the problems of space travel within our Solar System.