Radiation Risk and Exploring Mars
Collateral damage from cosmic rays increases cancer risks for Mars astronauts, University of Nevada Las Vegas
“Galactic cosmic ray exposure can devastate a cell’s nucleus and cause mutations that can result in cancers,” Cucinotta explained. “We learned the damaged cells send signals to the surrounding, unaffected cells and likely modify the tissues’ microenvironments. Those signals seem to inspire the healthy cells to mutate, thereby causing additional tumors or cancers.” Cucinotta said the findings show a tremendous need for additional studies focused on cosmic ray exposures to tissues that dominate human cancer risks, and that these should begin prior to long-term space missions outside the Earth’s geomagnetic sphere.”
Accepting More Personal Risk In Space Exploration, earlier post
“People who engage on expeditions to risky and dangerous places on Earth regulary waive certain safety and medical regulations in order to participate. I have done it more than once in the arctic and at Everest. You consider the risks, weigh the benefits, and then sign the forms. There are lifetime radiation exposure limits for astronauts that are supposed to be used to guide the selection of ISS crews. Now, these limits are apparently subject to selective waiver.”
In all reality, it cant be any more dangerous or have worse odds than of being hurt, maimed or killed while driving in one of those little collapsible metal and plastic boxes we all jump in every day. At least pilots do a pre-flight checkout of their conveyances. Who does that with a car? Suck up the risk, prepare tools and people as much as possible, hold everyone accountable for their work and behaviors, and get this Mars ball rolling.
If, as a driver, you think cars are dangerous, try being a pedestrian.
Bit that’s part of the point of the work, that we don’t understand the risk. We don;t know if it’s more or less dangerous and by how much, so useful analogies can’t be made at this point.
No, and we can make analogies at this point. We know the previous estimates of the radiation risk. We know that this study found that the risk is a factor of two greater. This study did not find that the risk was ten times greater than previous estimates. It did not say it could be anything. By the driving analogy, this uncertainty is on par with whether you are driving in Kansas, New York or Mexico. Not whether you commute or play it safe by working from home.
As I understand this issue on the level of an interested citizen, there are two primary sources of radiation in solar system space: the mysterious ‘cosmic rays’, and episodic solar outbursts.
AMS characterizes cosmic rays with energies from 10 to around 200 GEV or so, at least in the environment of the ISS. I don’t know if these energies have been attenuated by Earth’s magnetic field, or if these numbers can be reasonably extrapolated to interplanetary space, which I suppose is the issue we are discussing.
We have dozens of spacecraft in the solar system, with many more to come. What if we’d included the appropriate sensors on each (remembering that, yes, some did include this type of instrument)?
With time, a database with credible depth could be assembled. Are the sensors and associated power requirements quite complex?
We have those measurements. Spacecraft like the Advanced Composition Explorer, at the Earth-Sun L1 point, have instruments to measure these particles (to study things like solar coronal mass ejections and cosmic ray acceleration processes. The RAD instrument on Curiosity was specifically designed to measure the radiation exposure astronauts would have to deal with, both on the way to Mars and on the surface. That’s why I said we do have these data, and why I said people asking for more money to study this (specifically before human trips to Mars) were being less than honest.
What we don’t have enough data on is the relation between the physical flux of particles and the medical effects. We can say how many 300 MeV iron nuclei would be hitting an astronaut per square centimeter per second, how much of their energy would be deposited in what volume of tissue and how much a given sort of shielding on the spacecraft would change things.
Unfortunately, we also know that the medical effects depend on the particle. The same ionizing energy per unit volume from 100 keV electrons doesn’t have the same medical effects as that energy from 1 GeV iron nuclei. That probably adds a factor of a few in uncertainty to risk estimates.
I don’t think that’s enough to a risk of cancer later in life to serious problems during the flight itself. But an astronaut would probably like to know if it’s a 3% added risk of cancer, or a 30% added risk. Someone planning to move to Mars would definitely want to know if he will have to spend 75% or 95% of his time inside a buried habitat.
The data does not exist. The risk assessment uncertainty includes nuclear bomb affects extrapolated to deep space, where the energies are higher but way less frequent. The approach taken is multi-pronged.
Shorter trip time: although less efficient, shorten the trip time from 6 to 3 months with direct shots.
Gradually extend stays in proper environment-L2 is ideal. L2 provides the lowest energy staging point for reuseable tugs to the vicinity of Mars and asteroids.
Adapt an architecture that can preposition supplies and propellant to lower costs. F=ma: Not taking the gas+ supplies on departure increases the acceleration.
Long term: perform R&D of lightweight GCR protection (medicine, barriers, …) ISRU to reduce costs.
“For the benefit of all” not just grumpy old men who have more tolerance to GCR.
With our present state of knowledge, it would be immoral and unethical to send astronauts to Mars without better knowledge of the space radiation and other space environment effects on the human body.
This is to be done by sending crews to first the Moon, then longer trips to near Earth asteroids, and finally only then to long duration missions required for Mars. We also don’t fully understand the long term effects of weightlessness and other space environment effects we don’t currently understand.
Low Earth orbit is different from the moon, which is different from true deep space.
Its one thing to take large risks and scale a mountain Its another to go to the top of Everest without any special equipment or clothing and expect to survive and thrive. Going to Mars should not be the equivalent to playing Russian roulette with a fully loaded semi-automatic hand gun. And there is no form you can sign to make it safe. We need more knowledge, and we need to get that knowledge from the only place we can get it, from experience.
We need to be adults and consider that it may be suicidal to send crews to another planet. Given the current state of knowledge, this is a real possibility. Denial is not the correct approach.
By writing things like “playing Russian roulette with a fully loaded semi-automatic hand gun” you are implying a trip to Mars would certainly be fatal. The report in question doesn’t say that. The expected risk is, based on most estimates, a few percent increased chance of cancer later in life. This recent study says the risk is twice that. That’s hardly certain death.
Also, no one is talking about signing a form to “make it safe.” Keith is suggesting that rational people can, and often do, take risks and do things which are _not_ safe. A free, solo climb to the top of El Capitan is definitely not safe, and arguably less safe than a few percent increased risk of cancer. Someone just did that climb. There was no one in the press coverage saying he should have been stopped for his own good, or that he should have been treated like a suicide risk.
One valid issue is informed risk taking. If someone recruits Mars colonists while misleading them about the risks, I think everyone would have a problem with that. But there will always be unknown risks. At least, there will be until travel to Mars becomes common-place. The same can’t be said about free solo climbing. How do you inform your Mars crew of the risks you don’t know about, and how do they consent to them? I think it’s both possible and ethical, but it would require clearly informing them about the things we don’t know.
The biggest unknown is the long term effects of zero-g, followed by lower g, followed by zero-g. As Keith can affirm, the lack of the centrifuge on ISS means we don’t know how much gravity is needed for good health. Is Lunar enough? Martian? Don’t know.
We already know that the long term residents of the ISS are nearly incapacitated after their return for varying lengths of time. Even some of the shuttle crews had problems functioning for a while after landing.
I do know that the safety folks at NASA have some very difficult to achieve requirements. It used to be required that a launch abort of Orion be safer than the ejection seats of the T-38s that the crew fly in. There were efforts to relax that slightly, but I don’t know if they were successful.
Could someone point me to a statistical survey about astronauts returning from long-duration stays in microgravity? I’ve heard many stories, ranging from “no significant problems” to “none of them can even walk for a week.” If I try to take a mean in my head, the stories come out to “a few people, after over six months in microgravity, have noticeable but not tremendous problems.” But that’s all based on stories. Does anyone have a reference to an actual study, including things like real data?
It may or may not be out there. NASA has to obey HIPAA and keep astronaut health data private. Anything they present has to be done in a way to prevent identification of the crew involved. So, without waivers, they can’t present anything but statistical data from larger studies. NASA is constrained to treat health data as securely as classified data.
An anecdote. When the requirements for Orion were being written, NASA wanted a way to set up a totally private communications link (audio and/or video) from a crewmember to the physicians on the ground. It was part of shuttle protocol to have private audio talks between crewmembers and the docs in the hours after reaching orbit and as needed after that. For Orion they wanted it set up such that the other crewmembers couldn’t hear what was said. In a capsule with interior space equivalent to a minivan. With (at the time) up to 6 total crew. When I suggested that it could be solved with a simple HIPAA waiver signed by the crew, the medical staff was indignant. In the end, they agreed to a headset for the crewmember and the curtain that was in the design for the toilet. As with all telemetry, the comm channel would be encrypted.
Thanks for reminding me of the privacy requirements. On the one hand, I realize how important it is. If an astronaut isn’t well, it is a very good idea for him to talk to a doctor. Without privacy and doctor-patient confidentiality, that is less likely. Career (reflight) prospects discourage that. At least, I hope, we are beyond the fighter pilot, macho attitude of pretending to be too tough to get sick. But no one likes to say they are ill when the whole world could be listening and tweeting about it.
On the other hand, for medical/biological studies this privacy is counterproductive. Worse, it’s pointless. I know people who were interviewed by psychologists after wintering over in Antarctica. The resulting publications were very careful not to give names and tried to preserve the subjects’ privacy. But it was a farce. The number of people involved was so small that everyone could tell who was who. The privacy amounted to privacy from the general public but not from colleagues.
The same is true of the sociologist I mentioned in a different post. She did study how scientists working on the Cassini project interacted with each other and with the engineers at JPL. I haven’t read her papers on the subject, but I am sure of two things. First, she would have done everything proper, by both professional and ethical standards, to preserve people’s privacy. Second, anyone on the project could easily connect the published facts to a particular person. We aren’t a big group, and we all know each other moderately well.
Similarly “Biomedical Results of Skylab” identifies subjects by crew position rahter than name, but in reality their identities are not concealed.
That said, the simple fact that after all these years the effects of spaceflight haven’t dissuaded anyone who had a chance from going is pretty strong evidence that the risk is acceptable to people who have detailed knowledge.
The Russians used completely unofficial code words worked out in advance between the crew and thier physician (who was chosen by the crew!). This is described in “Diary of a Cosmonaut”.
Humans have experienced as much as 14 months of 0-G on the ISS and could stay for much longer. The effects of partial G will not be worse than the effects of zero G. Radiation appears at present to be a more significant problem.
The key is how debilitated you are after that long. Unofficial reports are that after a long tour on ISS, you are unable to do much for weeks to months after landing. So, how well will a crew sent to Mars be able to do any kind of strenuous work – assembly of a base, even getting on and off suits for EVA? We just don’t know.
The effects of partial G will not be worse than the effects of zero G.
That’s unknown. Given how tricky biological systems are, I would think there is a good chance that some systems would get back to normal, some might not. The mix of how systems respond would be unpredictable and could be dangerous. That’s why dropping the centrifuge on ISS was a bad decision for long-term exploration.
And yes, radiation is the obvious problem.
Would a human Mars mission be suicide or just a small increase in cancer risk? Until we do several missions, we don’t know. From what we now know, it is my opinion that suicide is more likely than small increase in cancer risk.
The only way to do this in a relatively safe and ethical manner is to increase mission length beyond what is known in smal to medium steps. And this will take time and money. Sorry, the alternative is to risk the crew’s life to save money.
Go build things to fly in the interplanetary space environment for 10 years, then come back and tell me I’m wrong. I think that will change or modify your mind.
And this entire discussion ignores several other ideal issues, like other non-radiation effects on the human body.
No offense, but I think that you answer represents the problem. You seem to think that _we_ should decide what is and is not acceptably safe. (“Until we do”, “we don’t know”, “from what we know”)
The other side of this debate is that the choice is a decision by the people who are personally taking the risks. That position is that we have no business making that choice, and it should be left up to the individuals involved. From an ethical standpoint, you are denying people their right to make their own decisions and to live their lives in the manner they wish.
As far as “go build things to fly in the interplanetary space environment for 10 years” is concerned, I have. Admittedly, unmanned spacecraft, but I do have some small knowledge about the space environment.
Consequently I have repeatedly bugged you about getting more powerful radiation resistant computers and more capable AI for your “unmanned” probes. The human brain is less impressive when you have to deal, as I do, with all the failures that people make of their lives. As a physician who has studied the brain, I just don’t see much in there that could not be duplicated in an artificial system, probably with better reliability. It just takes fast hardware and subtle code. NASA is SFAIK the only agency which has an absolute need for AI because it operates robotic spacecraft at distances too great for effective teleoperation.
A remarkable statement, one popular in the SF world but one not shared by many of your colleagues.
Not being learned in this area I’ve accepted on faith that the brain would be replicated, one day; that we would prepare personal ‘backups’ (a notion exploited by Jack McDevitt in many novels); that we would at some point choose between a natural life or one embodied in a large, perhaps quantum, computer that would give us the immortality we seem to want.
In the same breath a wonder about the assumed reductionist notion that we can be summarized in a binary world. The brain appears to be an analog device. These past decades though have been characterized by a slavish deference to ‘binary thinking’, a notion initiated by the transistor and her kin, and now adopted far afield.
The universe though appears to be something else entirely. and now this comment is far afield as well…
I read a recent article where researchers say that their work on brain architecture shows that it creates structures that operate in up to 11 dimensions. They are using something called algebraic topology.
https://www.nytimes.com/201…
A great piece about the aforementioned rock climb.
Not to make to fine a point, but one cannot play Russian Roulette with a semi-automatic pistol because it has no chamber to spin. A revolver is required, fully loaded or not. I make this point because we must all strive to be objective even when it seems tedious.
In the case of radiation injury, the risk is not precisely quantified but for a single trip to Mars and back the risk is in the 3 to 5 percent range, higher than current NASA standards allow but comparable to other risks the crew is willing to accept, and not nearly as bad as even conventional Russian roulette (16.67% for a six-chamber revolver with one chamber loaded). For a twenty year career on Mars and in space, let alone an entire life, the risk is almost certainly too high, due both to cancer (due mainly to solar protons and secondary X-rays) and to the death of brain cells (due mainly to heavy, fully-ionized iron nucleii present as galactic cosmic rays). GCR doesn’t usually cause cancer because the flux is low and the particles are so energetic that passage through a cell nucleus will likely induce so much genetic damage the cell will die, and dead cells do not cause cancer and in most tissues can be easily replaced. Ironically the brain is highly resistant to radiation induced cancer (because neurons do not divide, and cancer affects dividing cells) but the brain is susceptible to GCR induced cell death because even the small number of neurons that are killed each month cannot be replaced.
So whether the risk of radiation is excessive depends on whether we want “flags and footprints” or permanent habitation. For the latter, much better radiation protection is essential, possibly a combination of electrostatic and superconductiong magnetic strategies.
I would find this, and a very large number of studies into possible Mars missions, far more convincing if it didn’t finish by saying, “the findings show a tremendous need for additional studies… and that these should begin prior to long-term space missions…” In other words, “My research proves NASA must spend more money on the sort of research I do, and must do so before proceeding with their big plans.”
I know most of the people involved mean well, but there is a backdrop of very cynical attempts to extract more funding for their field. In some cases (measurements of the radiation environment, as opposed to its biological effects) I know that’s not necessary and basically a funding ploy. I’d feel a lot better about this sort of thing if people occasionally reported, “We looked into it, and it’s not a problem. You don’t need to renew our grants; we’ll go and work on something else from now on.”
You must be experiencing the same rain-blahs we are having over here on the west coast…15.5″ so far at my place, along with gray sky and a grumpy attitude 🙂
Michael,
I think you lost me, other than your comment about a grumpy attitude and my remark about being cynical. In my case, the cynicism isn’t due to the weather, as you may have implied. I’m currently between a project meeting in the Netherlands and a conference in Sweden. The weather in northern Europe has been unusually good. I’m sorry if it has been worse in Florida. Bad weather can affect people’s views, but in this case, I’d attribute my cynicism to personal psychology and/or a knowledge of history. But not the weather.
Naturally if you are studying something that is arguably important, an importance based on what little information is available so far, but that area is also generally ignored, the conclusion will be there needs to be more study, applying more resources. This is to be expected.
If the studies like this lack anything it’s the bluntness at the end to say NASA is not really planning for Mars much, if at all. The Mars window dressing is not real. NASA does like the fluff of saying it’s going to Mars, someday. So important questions can start, small studies can try to understand important questions. But real progress needs real resources, and NASA’s spending is all on a jobs program called SLS/Orion right now, not on Mars.
The same goes for the effect of gravity, or lack thereof, on the human body. If NASA were really going to Mars anytime soon we’d see significant resources going toward all manner of studies and projects to mitigate zero gravity. We’d have a project for seeing how to safely spin spacecraft, another for assorted shielding approaches with real data collected from real spacecraft and instruments in deep space, another for seeing how to shorten trip times. Instead we get a so-called “Gateway” that pretty much ignores all these questions. Why, because all that work ended up with was some PowerPoint that makes people think they are going to Mars. And that’s all management would accept as a product.
So, more study needed? Yes, as in more seriousness.
I agree that NASA, if it’s serious about sending people to Mars, needs more and better focused research. But this is not an example of that.
The study says the risks from radiation could be a factor of two greater than currently estimated. The current estimate of that risk is a few precent increased chance of getting cancer later in life (a 3% increase, if memory serves.) That’s worth knowing, but it amounts to saying that the first person to walk on Mars will probably get cancer by the time he (or she) is something like 60, rather than 75 years old. And the uncertainty is whether it’s 55 or 65. Do you really see this as a “go” or “no go” decision for a Mars mission? I don’t. But the statement about the need for more research (and funding to the people making the statement) implies that we absolutely can not send people beyond Earth orbit without this information. I’m sorry, but that’s just a ploy to get funding for interesting but non-critical research.
To me the risk of a single flight to Mars and back is la fraction of the risk of death due to a spacecraft failure. However if we expect to ppulate Mars and remain there our entire lives, the risk will not be acceptable. A combination of magnetic and electrostatic shielding is a possibility. However within our lifetimes AI will equal or surpass our own abilities at exploration, in dealing with the unexpected, and perhaps equal humans even in the sense of wonder they will feel and convey to those of us on Earth. How soon humans will reach Mars and how long they will stay will depend more than anything else on our definition of human.
Radiation is just one of the risks associated with a Mars mission. In spite of this, NASA leadership continues to spend billions in developing hardware knowing that we have ZERO data demonstrating that we feed and care for a crew for 20+ months missions. NASA Life Sciences has been underfunded and mismanaged for the last 15 years, focusing on fundamental research instead of driving out answers and responses to the bone, muscle, blood and productivity problems that have been known for the last 40 years. Staying with the JSC approach of ” build it and they will come” locks us in to years of made up missions ( asteroid rendezvous) and a forced return to the moon since we can’t perform a manned Mars mission unless were towing a Safeway and health clinic behind the crew capsule.
NASA was doing Mars base planning on feeding crew for long duration missions. It was collaborative among several centers and was going to culminate in some ground tests lasting up to a year in a test facility, Goldin cancelled it.
I guess I’m missing something. Why, exactly, do we need to study how to feed people on long duration missions? We’ve done that many times, and figured out how to do it right. It’s not as if we are back in the dark ages before Cook found that sauerkraut prevented scurvy, or Shackleton found out that over-cooked seal liver did not. These days, even on spacecraft, we also have refrigerators. So, when it comes to feeding a crew on a long duration mission, what do we need to study?
The project was to look at setting up a self-sustaining base on Mars. Using plants to grow food, recycle waste, convert CO2 to O2. Taking all the food you need for a nearly 2 year mission is a lot of mass to land on Mars. Plus the added mass of chemical air revitalization. Google Bio-Plex for more information on it.
Ok. That makes more sense. Personally, I think there is more benefit from closing the gas and water loops. Dehydrated, food is well under a kilo per person per day. For two years (call it 500 kg per person with an open loop), the equipment for growing food would probably be more mass and complexity than just shipping food as cargo. But it’s worth knowing about, since growing food would be extremely useful for longer stays.
Microgravity and radiation are concerns, but I don’t think “feed and care for” is a serious problem. We have been feeding and accommodating people on long-duration voyages for over a thousand years. It might not be comfortable or completely safe, but I think we know how to make it survivable.
With crazy Donald in charge the radiation risks are rather high down here too.
During the design of the LEM, NASA needed to design the ‘legs’ of the beast. Scientists far and wide were sought as they worked to characterize the nature of the lunar soil. Some thought it would be a fine dust, perhaps 10s of meters deep.This was easily supportable by imagining aeons of micro meteriorites churning regolith into a sandy beach. Or worse, talcum powder. Others, the opposite (I was in the green cheese camp).
The point is: they didn’t know. It’s what I think about when I read these reports that go over and over the same ground. In the end, NASA send Surveryoer/Ranger and actually obtained data.
According to one history I read, the Apollo LEM engineers just gave up and said, “For all we know, the Moon is just like Arizona. Let’s design the thing to land on a surface that’s just like Arizona.” In practice, they had to assume something, and that wasn’t all that bad a guess. Of course, now that we know the answer, we could design a more efficient lunar lander. But that’s your point: One the first trip, you don’t know everything and have to make some guesses. Then you learn, and can do a better job the next time around.
The anecdote to which you refer comes from Caldwell Johnson in Murray & Cox’s The Race to the Moon. I believe the more accurate quote from him was ‘It’s got to be just like Arizona.”
I heard one scientist involved with Apollo planning indicate (he was countering something I said in a presentation back in my student days…something quite close to the suggestion being made here, in fact) that the scientific community was highly confident regarding the bearing strength of the regolith even prior to Surveyor’s touchdowns, suggesting that those who pushed notions of oceans of dust, etc, were far outside the mainstream. I’ve seen similar perspectives in other histories.