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Dr. Charles Limoli, Tuesday, 7-7-15 July 8, 2015

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Dr. Charles Limoli, Tuesday, 7-7-15

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What Happens to your Brain on the Way to Mars

Guest: Dr. Charles Limoli. Topics: We discussed space radiation in the context of his paper, “What Happens To Your Brain On The Way To Mars?” Please direct all comments and questions regarding Space Show programs/guest(s) to the Space Show blog, https://thespaceshow.wordpress.com. Comments and questions should be relevant to the specific Space Show program. Written Transcripts of Space Show programs are a violation of our copyright and are not permitted without prior written consent, even if for your own use. We do not permit the commercial use of Space Show programs or any part thereof, nor do we permit editing, YouTube clips, or clips placed on other private channels & websites. Space Show programs can be quoted, but the quote must be cited or referenced using the proper citation format. Contact The Space Show for further information. In addition, please remember that your Amazon purchases can help support The Space Show/OGLF. See www.onegiantleapfoundation.org/amazon.htm. For those listening to archives using live365.com and rating the programs, please email me as to why you assign a specific rating to the show. This will help me bring better programming to the audience. We welcomed Dr. Charles Limoli to the program for this 90 minute discussion on space radiation and astronauts, especially flying in deep space, going to Mars or back to the Moon, evening residing on the Moon or Mars. You can read his paper which has been uploaded to The Space Show blog for this program. During the first segment, Dr. Limoli outlined the basics of his research. Before going deeper into the topic, I asked him several questions about the use of rodents and mice for the experiments, the possible use of other animals, the constraints and limitations of radiation simulation experiments, plus how these radiation experiments and doses differ from humans getting radiation treatment for cancer or other medical problems. We had quite the discussion on rodent brains compared to human brains, animal experiments in general, plus the protocols used in his experiments which were all carried out at Brookhaven. By the way, Dr. Limoli is a space advocate, he has received NASA funding for years, and he and his team have a great interest in radiation issues for human spaceflight. Dr. Limoli then took time to tell us how the experiments were conducted. Some of the discussion is technical so I suggest you read his paper which has been placed on TSS blog. Dr. Limoli went into significant detail to tell us how they conducted the experiments, applied the low dose radiation to the subjects, and how they evaluated the results. Don’t miss his description and analysis of the experiments. He said the changes were subtle measured 6-8 weeks out but he also said future papers may show that the cognitive changes continued to happen over a much longer period of time. In response to one of my questions, he said there was no sign of recovery. The primary changes that were observed and reported in the paper had to do with cognitive impairment which we discussed in detail throughout this program. I asked our guest about age, gender, race, and cultural differences. I also asked if NASA was now doing or might do in the future some genetic screening to find those best suited for a high radiation environment. Space settlement risks were talked about as was childbirth and pregnancy. Dr. Doug from S. California called to talk about GCR shielding. He wanted to inquire about using the stuff on the mission, food, water, supplies, etc. for shielding. He suggested the strategic placement of the stuff to maximize shielding. Dr. Limoli did say this was all factored in but that GCRs are non-directional so they come in from everywhere so such “stuff” shielding would only be partially helpful in protecting against radiation. For now, it would have to remain an unanswered question pending getting more research data. In this discussion, Dr. Limoli did explain the components of GCR and what they do to the body and the brain’s cognitive ability.

In the second segment, we took listener questions including several from our friend Dr. Logan. One such question wanted to focus on how deep you would need to go into the Martian surface to equal the protection of Earth’s radiation shielding. Our guest was not sure of the actual calculation but estimated 4-5 meters. Tim in Boston sent in a note quoting what Dr. Zubrin said about Dr. Limoli’s research project per his critique of the paper published in The Space Review May 11, 2015. Dr. Limoli said that what Dr. Zubrin was saying was wrong regarding the details of the experiment. It was a very interesting discussion so don’t miss it. Rhonda wanted to know what Dr. Limoli would say to Elon Musk were he charged with consulting for Elon for his Mars plan and desired mission. Don’t miss what he said he would tell Elon. Later in the segment, I asked our guest to connect the dots with radiation issues and the other human factors medical conditions. This too proved to be an interesting discussion so don’t miss this one either. Charles was asked to talk in more detail about the observed cognitive changes and the actual tests used to reach their conclusions. In his closing remarks, he stressed how important continued research was and strongly urged listeners to support science research, write our congressmen and women, lobby for and advocate more research as it is the research that will give us more information to mitigate and resolve our spaceflight challenges.

Please post your comments/questions on TSS blog above. You can reach Dr. Charles Limoli through me.


1. J Fincannon - July 15, 2015

Another reference that somewhat refutes Dr. Limoli is:
Published in July 2014.
Space radiation risks to the central nervous system
Francis A. Cucinotta, Murat Alp, Frank M. Sulzman, Minli Wang

Here are relevant excerpts:

Galactic cosmic rays (GCR) may alter astronauts cognition during space missions.
GCR may increase central nervous system (CNS) risks including Alzheimer’s disease.
Experiments at particle accelerators have used animal models to estimate CNS risks.
Results show that doses used are too large to understand human CNS risks.
Experiments testing for thresholds at low dose-rates with particle beams are needed.

At this time, reliable projections for CNS risks from space radiation exposure cannot be made due to a paucity of data for particles types, doses and dose-rates, and lack of understanding on the extrapolation of experimental results with rodents to humans. The existing animal and cellular data suggest that space radiation can produce neurological and behavioral effects, and therefore the possibility exists for impacts for a Mars mission or other long duration deep space missions. However possible dose thresholds for these effects, and the significance of these results on the morbidity to astronauts has not been elucidated. It is to be noted that the studies to date have been carried out with relatively small numbers of animals (typically <10 per dose group), and therefore testing of dose threshold effects at lower doses … that would occur on space missions has not been carried out to a sufficient extent at this time and will require much larger group sizes. Furthermore, studies with relatively few GCR species and at energies above 1000 MeV/u have not been made, nor studies with mixed fields of protons, neutrons, and HZE particles. …

The majority of CNS studies have been carried out at doses of 0.5 Gy or more, while many of these studies suggest a lack of significant effects. However (various) studies … indicate significant effects for acute HZE particle or proton doses as low as 0.1 Gy could occur. Certainly studies with a variety of HZE particles, simulating chronic radiation conditions, and for longer follow-up times are vitally needed in addition to the results reported to date.

Because of the uncertainty in extrapolating dose thresholds from rodents to humans, we estimate that if a dose threshold two-times higher than the expected HZE particle dose for a Mars mission near solar minimum were established it would ensure safety of crew for a Mars mission with additional considerations of the effects of low LET GCR and SPE exposures. However current data is uncertain as to a threshold dose for clinically significant CNS effects, with estimates as high as 0.5 Gy to as low as 0.1 Gy of HZE particles possible. Reducing the uncertainty in this assumption through space radiobiology research would likely lead to a significant costs savings for space missions due to the possible mission impacts of an acute CNS risk limit with large uncertainty. A dose threshold of 0.2 Gy of HZE particles or higher would ensure that no significant in-mission CNS effects to Mars mission's crews would occur. Shielding would be an efficient countermeasure to higher doses from SPEs. Additional considerations are needed to limit possible late effects, which should be included in life-time REID limits…

2. J Fincannon - July 15, 2015

I found a good reference on the visual effects seen by astronauts at LEO and beyond. I seems like it was not completely settled what was being affected. Could still be the visual cortex. I also recall reading somewhere that astronauts slept near the batteries on Mir and ISS to get more shielding to prevent the irritating flashes.

Here are interesting relevant excerpts from the reference:

“Positive visual phenomena in space: A scientific case and a safety issue in space travel”

“Most astronauts on Apollo, Skylab, and MIR reported ‘flashes of light’ occurring in different shapes and apparently moving across the visual field, in the absence of auditory, somatosensory, or olfactory abnormal percepts. A temporal correlation with heavy nuclei or protons has been documented in space and comparable phosphenes were observed by volunteers whose eyes were exposed to accelerated heavy ions at intensities below the threshold for Cerenkov visible radiation. An interaction between heavy ions and the retina was suggested. However, the biophysics of heavy ions or protons action remains undefined, the effects on photoreceptors and neuroretina have not been differentiated, and some direct action on the visual cortex never ruled out.”

“The evidence that phosphenes can originate from direct stimulation of neurons in the retina, optic nerve, or cortex raises questions that directly relate to the visual positive phenomena (light flashes) observed in space.”

“… the extent to which the perception of phosphenes in space only depends on the high energy deposited by HZE particles virtually absent on Earth surface remains undefined. Functional brain adaptation to microgravity could affect sensitivity as well and may account for some enhanced response of the visual system to particles (or other factors) otherwise ineffective at ground level. Effects on other higher brain functions (such as cognitive processes related or unrelated to vision) would also be possible, at additional astronauts’ risk.”

“Further studies are in progress to document the electrophysiological concomitants of the light flashes observed by astronauts onboard the ISS and to investigate the biophysics of particles interaction with the retina (photoreceptors membrane, photopigments, or inner neurons), optic nerve and cortex in animal models and humans.”

ISS RESEARCH: “The ALTEA research project investigates the effects of particles on the visual function in space. A facility of the International Space Station (ISS) to be made available to the international scientific community (for human electrophysiological and psychophysics experiments, studies on particle flux, and dosimetry), ALTEA combines a multi-channel electrophysiological recording system, a computer-assisted visual stimulator, and a whole-head large solid angle silicon detector identifying particles charges, trajectories, and transferred energy at discrete locations in the eye and brain.

3. B John - July 11, 2015

I think neurobiology should focus on the difference between brains which want to go to Mars, and brains which imagine it impossible. The huge majority which is indifferent could be the control group.

4. DougSpace - July 10, 2015

The study design was, for practical reasons, so different from what would happen in a real trip to Mars that ut’s hard to tell whether the findings are relevant or not. What we really need is to place lab rats out into cis-lunar space beyond the radiation belts for a period of months. But this would take significant money and time.

Rather, I think that we should figure out an interplanetary craft design that would have enough shielding to likely make the issue irrelevant. We would want to do this anyhow in order to reduce the risk of inducing fatal cancers.

This NASA graph:

indicates that 10 m3 per crew member is more than tolerable and can allow crew to perform their necessary functions. For an initial Mars flyby mission with a crew of two, this comes to a space of 2.7 m per side of a cube. Using Logan and Adamo’s choice of about 50 cm thick of water shielding, this comes to about 32 tonnes of water-bearing material. That’s well within the range of an SLS or Falcon Heavy with ion propulsion to an EML staging point. Since this water-bearing material could be food / water provisions then some of it would not have to be additional mission mass.

This NASA graph:

seems to indicate that the 50 cm thick shielding would reduce GCR exposure by about 60% and that amount of thickness would nearly completely block the solar cosmic radiation including SPEs. If my understanding is correct then the 50 cm shielding would reduce the total radiation exposure by about 80% which would bring it to about ISS levels which we find acceptable.

So I’m not so concerned about Limoli’s findings. We just need to apply what we’ve long known about the radiation reduction effects of water when planning missions to the Mars system.

J Fincannon - July 11, 2015

In 2009, I had asked a space radiation expert about whether the water used to shield humans in a spacecraft would be safe to drink and the reply was that it would not be “activated” by the radiation so was safe. A subsequent question (never replied to) I asked was regarding food, namely, does irradiated food (by the radiation belt or GCR) remain safe to eat? I realize that some sort of ionizing radiation is used to kill bacteria on food on Earth, so surely that is safe. But then clearly cattle and plants near Fukushima are not safe to eat (I imagine this is more due to contaminants than irradiation). So can someone answer, does food get “activated” by GCR.

5. DougSpace - July 10, 2015

When readers of a medical journal send in letters criticising the methodologies of a paper what matters is not the qualifications of the readers but the validity of their arguments. Dr Zubrin brought up the legitimate issue of whether compressing the total radiation into a brief period of time has the same effect as spreading it out over the length of a mission. Dr Limioli didn’t argue that it didn’t matter. Indeed he agreed that it was a valid criticism. So Dr Zubrin’s criticism stands regardless of his particular credentials.

Michael J. Listner - July 10, 2015

And that’s the difference between Dr. Limioli and Dr. Zubrin: Dr. Limoioli is willing to discuss issues; Dr. Zubrin comes right out flames assertions that don’t support his vision of Mars colonization.

6. Michael J. Listner - July 9, 2015

I’m pretty sure Dr. Limoli said in no uncertain terms that even though his research raises concerns about radiation it does not mean it’s a deal breaker for Mars. Regrettably, Dr. Zubrin in his zeal has a tendency to attack viewpoints that challenge his vision of Mars exploration, which makes his dissent to Dr. Limoli’s research suspect and those who follow his passion tend to fall into the same trap of not listening to what is being said and instead hearing what they want to.

As for Dr, Limoli’s qualifications vs. that of Dr. Zubrin’s I would look at it from the perspective of qualifying a legal expert for testimony. Based on the fact that Dr, Limoli’s research is focused in this area, that he used acceptable methodologies to reach his conclusions, and he is published in peer-reviewed journals, I suspect a court of competent jurisdiction would qualify him as an expert in this area.

On the other hand, Dr. Zubrin is not a researcher in this area and apparently is not published in peer-reviewed journals in this specific area of research. That coupled with Dr. Zubrin’s clear motivation in promoting Mars colonization would make his testimony suspect and make his qualification as an expert open to question.

Posters can criticize me for these comments, but I do recall that Dr. Zubrin pulled no punches when disparaging Dr. Limoli’s research a few months ago on this Show. Fair is fair. Kudos to Dr, Limoli for agreeing to come into the lion’s den, and kudos to Dr. Livingston for again providing a unique guest and intriguing discussion.

J Fincannon - July 10, 2015

I think you provide a fair assessment. The “problem” may be that Dr. Limoli chose a controversial heading for his article. This may help get his work some notoriety, but is hardly the general bland, obtuse and general wording one would expect from medical research. Perhaps they have learned the rules of Internet click-baiting. After listening to the show, I am still confused about how mice brains are analogous to human brains (and more importantly how are they not analogous). I guess I just need to trust the expert. He suggested that because the brains going into space are mature, they will not benefit from cell replacement, so THIS is the reason it does not make a difference if the dose is in one lump or gradual over time. As a layman, it seems hard to accept. I keep hearing that people DO have some replacement of brain cells even at older ages. Also, the number of cells and number of connections and size of the brain have to enter in the picture. It is reassuring that he feels it relatively easy to deal with (only 5 years of research!!!). I would like to have a more simple minded comparison for us lay folk to understand, such as comparing the damage inflicted to the brain based on radiation to something most people can understand like drinking X number of beers a day over a Mars equivalent time duration.

Also, I wonder how the light phosphenes seen by Apollo astronauts (and ISS ones too) relate. Is this eyes (retina) or brain (visual cortex)?

It was not quite clear as to the mechanism. It sounded to me as if it was not cell death, but rather something else (the connections?).

Anyway, the show was a good start on understanding his work. We may need him back again.

7. B John - July 9, 2015

Medical people hate that their patients die or get sick(er). But all of us will anyway. So the ultimate question is: For what purpose do we live and die?

I certainly do appreciate that my surgeon does not compromise my survival for some other imaginary interests of “collective development for the future”! But an informed consent to use oneself to try out if one actually suffers this hypothetical “mad cow astronaut cosmic radiation syndrome” or not, should of course be respected. Maybe a tin foil hat helps? Was there a control group of mice with tin foil hats in the experiment this show was based upon? I would’ve added a control group of scientists with tin foil hats too, but I’m controversial…

8. lunarush - July 9, 2015

Let’s do a thought experiment. Transport yourself back to a time when snorkeling has just been discovered. Maximum safe human underwater time was unknown.

The following Investigative Question is proposed: How much time can be safely spent underwater while snorkeling?

Below are summaries of two investigations:

Ph. D. #1:

I can only afford 10 minutes of pool time at the ultra-sophisticated National Research Pool so I will put my human subjects under water for 10 continuous minutes. This is a minimum anticipated cumulative exposure for a useful snorkeling mission.

Research Finding:
10 minutes underwater is fatal to human beings.

Ph.D. #2

I can afford 6 hours of pool time at a cheaper, less sophisticated, pool. I will put my human subjects under water for 20 seconds followed by 20 seconds of above surface snorkel breathing.

Research Finding:

Several hours under water is no problem for the great majority of physically fit human beings. The human underwater time limit not found in this investigation.

When Ph. D. #1 is asked about Ph.D. #2’s conflicting results, Ph. D. #1 states I am a Qualified Scientist and asks how many peer reviewed papers has Ph.D. #2 published.

Which Ph.D. do you think has the better, more relevant Research Finding?

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