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Radiation Sickness, Cellular Damage and Increased Cancer Risk for Long-term Missions to Mars

Mission to Mars (NASA)
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.

Solar flares will be a problem for future colonists (SOHO/EIT)

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.

Energetic particle tracks in a bubble chamber (NASA)

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

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Hello! My name is Ian O'Neill and I've been writing for the Universe Today since December 2007. I am a solar physics doctor, but my space interests are wide-ranging. Since becoming a science writer I have been drawn to the more extreme astrophysics concepts (like black hole dynamics), high energy physics (getting excited about the LHC!) and general space colonization efforts. I am also heavily involved with the Mars Homestead project (run by the Mars Foundation), an international organization to advance our settlement concepts on Mars. I also run my own space physics blog: Astroengine.com, be sure to check it out!

Comments on this entry are closed.

  • Roger Brannon April 17, 2008, 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.

  • Dark Gnat April 17, 2008, 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?

  • Al Hall April 18, 2008, 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… :-(

  • Al Hall April 18, 2008, 10:45 AM

    By the way…….., nobody seems to have caught (or read) my DHMO rant on April Fools… I’m so disappointed.. :-(

  • Steven O Driscoll April 19, 2008, 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.

  • Al Hall April 20, 2008, 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.

  • Steven O Driscoll April 22, 2008, 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.

  • Asif May 7, 2008, 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.

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