I wanted a creature that produces something in its blood to protect itself from SEP (solar energetic particles) and GCR (galactic cosmic rays). The skin of the creature is normally sufficient protection, but the world has radiation bursts which can penetrate this layer, and necessitate a second line of defense.

I wasn't sure what sort of cell would be most effective for this. Possibly a variation of blood cells with a high iron concentration? Or, perhaps the creature could process other metals/minerals for this process, maybe even by processing some lead. Octopi process higher concentrations of copper, already.

Something like 0.05% of the blood is iron, so that's not much of a radiation shield. But then, that's just used to help with oxygen transfer, so cells specifically made to endure/block radiation and carry high metal contents might ferry larger percentages.

It's quite possible you'd be better off just growing more muscle in these areas, and having a cleanup crew to get rid of dead and mutated muscle after a radiation burst.

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    $\begingroup$ Don't waste your time with blood, do it the way evolution do and make it lead-infused sweat or skin pigment, which only get used when there is radiation nearby. $\endgroup$ Dec 29, 2017 at 8:48
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    $\begingroup$ @NamNguyenHoang That sounds very interesting. could you please elaborate that into a question? I'm unfamiliar with the examples you'e alluding to. $\endgroup$
    – Johnny
    Dec 29, 2017 at 11:08
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    $\begingroup$ On it: worldbuilding.stackexchange.com/a/101309/32360 $\endgroup$ Jan 3, 2018 at 4:34
  • $\begingroup$ Cosmic rays are extremely difficult to block. They basically pass through everything with little/no interaction. $\endgroup$
    – Rafael
    Mar 22, 2019 at 0:21

6 Answers 6


Blood is already just about as good a radiation shield as you're going to get. That's because it's mostly water, and water is a great shield.

Just like a bulletproof vest, the two main properties that you're going to want in a radiation shield are,

  • Being there.
  • Safely absorbing the energy of a collision.

It turns out that there are plenty of materials that are relatively safe when irradiated. (Choose the wrong one and your shielding is a breeder reactor.) Lead and water are two great examples. So, in stark contrast with the challenges involved with making bulletproof vests, the biggest problem you're going to have when designing a radiation shield is arranging things so that the sheild is there when a high-energy particle passes by.

I'll go straight to talking about neutron shielding because that's the toughest case.


As you may have heard, atoms are mostly empty space. Neutrons are neutral (meaning that overall they don't interact with electric fields), and they will only ever involve themselves with other matter through the weak and strong nuclear forces. Those forces are very, very short-ranged, and for all practical purposes only act over length scales around the size of a nucleus.

As a result, your neutron shield's biggest concern will be putting enough nuclei in the path of the radiation that the chance of it hitting the shield becomes larger than its chance of hitting the animal. You'll want to do this with relatively high-density materials. Once again, water and lead.

If you're willing to invent new materials, then your animal could have a shell of pure nuclear matter (like a neutron star.) It's strongly advised to put the material in a shell or on the animal's skin, because if its in the blood it will waste a lot of time being pumped around through internal organs that aren't supposed to have any radiation nearby in the first place.

Charged Particles

Charged particles (like electrons, protons and helium nuclei (alpha particles)) can be deflected by magnetic fields. If you're willing to take the hits from neutrons and photons, your creature can protect itself from the charged particles whizzing through space by filling itself with very powerful magnets. I could imagine some tiny blood-suspended superconducting crystals accomplishing this, although it might be hard to stop them from sticking together (clotting, if they're in blood) like magnets tend to do.


The biggest issue with ionizing radiation for living creatures, is damage to DNA. Any creature with a sufficiently redundant DNA sequence, and extremely active repair functions would be able to correct and heal any damage before any real issues.

See the wiki on radiation poisoning for more information.

@anon made a point that warrants an edit to add a link. There are two categories of radiation that must be shielded differently. Your approach must target the type of radiation you're worried about. radiation shielding overview

  • $\begingroup$ That is the biggest issue, yes. However, massive damage can disrupt the ability to heal the damage, as well as leading to other symptoms like radiation burns. For this reason, a preventative defensive system may be desirable, which is what I'm speculating with this idea. $\endgroup$
    – Johnny
    Dec 28, 2017 at 4:24
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    $\begingroup$ You're not going to get away from the burns. Radiation is high energy particles slamming into the atoms and molecules. Damage is going to happen. What you can do is rectify the damage in an expedient amount of time to keep from dying. $\endgroup$
    – Stephan
    Dec 28, 2017 at 4:28
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    $\begingroup$ I don't see why it wouldn't be. Many creatures have mineral deposits. Take the flamingo, the red in the feathers is directly due to diet. Could be that they've evolved to store deposits of lead in their carapace $\endgroup$
    – Stephan
    Dec 28, 2017 at 5:37
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    $\begingroup$ If you haven't already, check out en.wikipedia.org/wiki/Deinococcus_radiodurans $\endgroup$
    – David Elm
    Dec 28, 2017 at 19:27
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    $\begingroup$ And also this sciencealert.com/… $\endgroup$
    – David Elm
    Dec 28, 2017 at 19:29

They could grow shielding beneath the skin over softer, more vulnerable areas. The most immediate example that I have personal experience with is wild boars. They grow a thick, extremely tough, fatty shield beneath the skin in the areas of their front shoulders. Older, larger hogs, have shields thick enough to stop high caliber bullets. Also, the older and larger a wild hog gets, the thicker its skull gets. I have seen many large caliber rounds stopped by the skull over the years.

While stopping a bullet is vastly different from stopping radiation, perhaps a subdermal layer of fatty tissue could exist with a high enough mineral content to act as shielding. Also, extremely high bone density with additional minerals could protect many vital organs. Perhaps some special bones could encase arteries in certain areas to protect the blood, along with an organ that specifically filters radiation from the blood.

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    $\begingroup$ This was going to be my answer... Not in the blood but rather fatty tissue $\endgroup$
    – bendl
    Dec 28, 2017 at 18:05
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    $\begingroup$ Yeah, fat or muscle or bone may be better for this. Unfortunate I don't know what's best. $\endgroup$
    – Johnny
    Dec 29, 2017 at 0:53

You can make radiation shielding in the blood, but it's like hitting things with your head: You have better things to do with that body part

First, take a look at some candidates for radiation shielding materials:

  • Water (provided that they are in sufficient quantity, and not already obliterated from whatever planet they come from by radiation)
  • High A (atomic weight) materials (this include lead, mercury, gold, depleted uranium...), good for alpha and beta shielding
  • Neutron absorbing or shielding materials (hydrogen, boron...)

From the list above, the type of structure the creature used will need these quality:

  • Thick (to have enough bulk to just absorb the radiation)
  • Cover the whole body (or at least be there when you need it)
  • Preferably dead, if alive, it had better be tough (not only the radiations are deadly, the shielding materials (heavy metals, boron) are not much safer, so yes, the surest way to survive is not to)

And now, let's meet our contestants (all these examples are only against the sun, which have low radiation in the UV range, but the principle is the same, just add radiation shielding material from above):

1. Blood

  • Not very thick (there is only a thin layer of blood vessels under the skin)
  • Cover almost everything (skin cancer is a thing, too). At least they are always there when you need them
  • Vitally important to the body, and alive (Red blood cells and platelets don't have nuclei to be mutated by radiation, but they can be denatured and become useless. White blood cells do have nuclei and can be mutated, with consequences)

2. Sweat

  • Depend on skin structure, can be thick, or thin. There is an actual animal using this tactic to stave off the sun's radiation
  • Not always on all the time. Your creature will need a way to detect radiation and sweat ahead of time
  • Absolutely dead, and carry no risk of complication
  • Bonus problem: If you do so, your creature will look like a blood-soaked serial killer every time there is harmful radiation. Your call, but I find it awesome (Just kidding, the real problem is that the creature must devoted water and minerals on a disposable shield)

3. Scale, fur, feather, what-have-you

  • You can make them incredibly thick
  • Always there, always got your back
  • Dead as a doornail as well
  • Problem: Your creature is now a walking biohazard. Remember, most radiation shielding is also very toxic

4. Skin (or rather skin pigments)

  • Pretty much the same as sweat, except they are not on the outside of skin, so no resource are wasted, in return for being slightly alive (the epidermis cells is alive, but they can push the pigment to the outermost edge of the cells)

PS: This answer was inspired by Display Name's answer, and others' comments. I only consider mechanisms used by animals since Jonny ask about blood
PPS: Sorry for lateness/necromancy, I have a test in that time


On the same thread as Stephan:

There is no material that provides a life form total protection from ionizing radiation.

  • Any material can only block so much radiation. You could have lead armor 15 ft thick and not be able to block all radiation.

  • Any complex life form is inherently vulnerable to ionizing radiation. In order to support complex life your cell (be it organic or nanobot) must be constructed with complex molecules (like proteins) that can provide the different functions of that cell. Ionizing radiation is destructive because ionic atoms destroy these molecules thus destroying the cell. Imagine your car is a cell and blasting it wildly with an industrial sand blaster is radiation. When you damage enough or just the right pieces it stops working which is radiation poisoning.

This doesn't mean a creature cant be more resilient to radiation.

Radiation poisoning is lethal when you have enough cellular damage that repair is impossible. As in living cells cannot replace dead cells fast enough. So one way to increase your resiliency is to increase your regenerative abilities being able to replace more and different kinds of dead cells.

Thickness/density and depth helps too.

magnetic fields have also been able to deflect strong radiation.

  • $\begingroup$ ....15 feet of lead? If they could lift that into space, Astronauts would have no worries about radiation whatsoever. We established earlier that there are organisms that are not only more regenerative and redundant, but also more resistant. Lead is definitely used as a means to reduce radiation... $\endgroup$
    – Johnny
    Dec 29, 2017 at 0:52
  • $\begingroup$ Key word is 'reduce' not the same as 'prevent'. @anon you make a good point which brings up the distinction between types of radiation. I've added a link to my answer. $\endgroup$
    – Stephan
    Jan 4, 2018 at 18:57

I am just wondering if a snip of the tardigrades section of dna (that is responsible for successfully repairing outer space radiation damage) could be spliced into the stem cells of mice. If it works on lab mice, looking down the road maybe the human race could also be helped to be more resilient in a high radioactive exposure. Im just an old man who is constantly amazed at what the kids are doing today. Id like to see my kids one day get a shot and be impervious to radiation... Now that is a vaccine I could get behind.

Dave in

Stockton CA


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