Questions for scientifically knowledgeable posters.

[Thorgalaeg]

Ah, as the forum's #1 connoisseur of radioactive things, I love being asked these sorts of questions. The Wiki article on acute radiation syndrome has a lot of the answers you're looking for, as does the shorter one Biological timeline of radiation poisoning.

High doses of radiation kill in a variety of ways. One thing that happens is that the bone marrow is really radiation-sensitive, and white blood cell production collapses, leaving the victim extremely vulnerable to infection. It also messes with the ability of cells to divide properly, which produces major effects everywhere that a relatively fast turnover of cells is needed, such as the gastrointestinal system. The result is that people who have absorbed a fatal or near-fatal dose of radiation actually sometimes improve for a week or two and feel basically fine, until the cells that are supposed to be replaced aren't replaced and then they go into a rapid decline, dying at the 2 or 3 week mark. The effect on cell division is great if it's targeted at a tumor because we don't want tumors reproducing, but it increases the risk of cancerous mutations in non-cancer cells that do manage to divide as well, and at high short-term dose rates, the inability of cells that are supposed to divide rapidly, like bone marrow and the GI lining, leads to survival for a little while followed by a slow and painful death after a couple weeks.

At the sorts of extreme doses you are talking about, in the >25 Sv range (death in <48 h), ionizing radiation causes severe neurological damage as well. Victims here usually die of neurological complications before they die of the other ones. Cancer patients who have whole-brain radiotherapy to deal with multiple brain tumors will usually complain of a mental fog that eventually goes away, but at ten times that dose, the brain just starts shutting down pretty rapidly. I don't know the details of why this is, though.

Really nasty. And those 2 weeks feeling well while you know you are doomed makes it even nastier. BTW what would happen if you enter into Fukushima reactor building where it seems 600 Sv/h have been measured?

 

[Akka]

You could make a hybrid species which is not radiation-based per se, but radiation-resistant (repairs itself really fast) and able to use radioactive energy to power its metabolic functions. The mitochondria may have evolved to function like a nuclear reactor, etc.

That's one way I might end up going. I'd like to have the radiations destroying it as part of its life-cycle, though - I'm trying to have the species lacking the whole concept and perception of "pain", to make it even more alien (though I'll have to think about why it wouldn't be an evolution handicap).

To add to the last post, I'm thinking maybe some sort of photosynthesis that uses gamma rays (read: high-energy photons). Essentially have antenna complex molecules that can capture such photons and funnel them into th electron transport chain.

That was roughly the idea I was going for (though I'm not knowledgeable enough about, hence my asking, about why kind of radiations would be the most logical to be usable as energy/food ; and of course it also depends on which kind of radiation are present, though the more I think about it, the more the "radiation belt" of a gaz giant seems interesting).

I'll happily take information on this point (which kind of radiation could be used by an hypothetical lifeform, and how it could be used).

I'd also really like to have them using some sort of magnetic/electric field to funnel radiation toward their feeding organs, and that such fields would seriously compromise human technology - perhaps a form of EMP. That's a point which is pretty vague (how would a biological lifeform be able to create a powerful enough effect ? How easily could technology realistically be vulnerable to such field if it can be shielded against cosmic radiation and the like, which are logically much more powerful ?) and which will be hard to get right, though.

For radiation resistance, maybe the organism can readily metabolize heavy metals and incorporate them into proteins or deposit them like bone minerals.

What would make heavy metal interesting as far as radiation resistance go ?

Nuclear radiation is much more energetic than the radio waves used for communication and thus have a much higher frequency. So in principle, radio communication is no problem in a highly radioactive area, with two caveats: First, your communication equipment needs to be able to withstand the radiation (see below). Second, if the radiation source is a star, it might also emit other radiation at lower frequencies that does interfere with the communication. But you could always get around that by using radio waves in a narrow band with high power.

Thanks for finally answering this point, it looks like it let most people at a loss

It seems we can rather easily communicate with man-made space-faring vehicles (like the probes which sent back images from Neptune, or the Mars rover and so on), so I'm not sure a star cosmic rays would actually hamper radio communication in any noticeable capacity (at least, it seems to be easily compensated with 70s technology, so even less of a problem for a close-future one).
I was wondering about something like remotely guiding a robot on the surface of the planet, and could the radioactive background be sufficient to cause interferences and so on.

If you build semiconductor electronics, you intentionally introduce defects in the semiconductors. Given the right pattern of these defects, the circuit will do what you intended. Nuclear radiation will introduce additional defects in the semiconductor, thereby altering the pattern. If the radiation alters the pattern too much, the circuit will do something else than intended, usually resulting in a breakdown. if you keep this in mind, you can design circuits that are not as susceptible to radiation than usual equipment, but fundamentally, every semiconductor circuit will fail if subjected to too much radiation.

Thanks, that was a point I was wondering about.
If you had to build something to work in a high-radiation medium, how would you make it work ?
Would simple material shielding be enough, or would it require something more intricate (like specially-designed circuits you describe) ?

 

[uppi]

I was wondering about something like remotely guiding a robot on the surface of the planet, and could the radioactive background be sufficient to cause interferences and so on.

This should be no serious problem as long as you can keep the robot functioning.

Thanks, that was a point I was wondering about.
If you had to build something to work in a high-radiation medium, how would you make it work ?
Would simple material shielding be enough, or would it require something more intricate (like specially-designed circuits you describe) ?

Shielding is good, because you can get rid of the most damaging radiation, but you cannot shield everything. So I would use a combination of shielding and specially designed circuits. I am no expert on this, but I would not make them as small as I could, but larger and more robust. The elements of the circuit would have to be spaced further apart to reduce radiation induced shorts. Using materials not as susceptible to radiation damage would also help. Finally, the circuits should have multiple redundancies to prolong the life of the whole system. The result would be a circuit that is slower and consumes more power than a regular circuit. All these measures can increase the time a robot could spend in a high-radiation environment, but not prevent the ultimate breakdown.

 

[Thorgalaeg]

You could make a hybrid species which is not radiation-based per se, but radiation-resistant (repairs itself really fast) and able to use radioactive energy to power its metabolic functions. The mitochondria may have evolved to function like a nuclear reactor, etc.

Already invented by mother nature. Chernobyl and Fukushima have been colonized by a misterious black substance which turned to be radiotrophyc fungus. It seems pretty happy to grow in absurdly high radiated environments. They have large concentrations of melanine to absorb radiation and can even use it as energy source to the point it does not grow nearly that fast anywhere else.

 

[SS-18 ICBM]

What would make heavy metal interesting as far as radiation resistance go ?

It's the principle behind the use of lead for shielding. Dense metals with nuclei bristling with protons and neutrons that stop energetic photons cold. Keep in mind this won't work for beta particles, since the collision produces those same photons in X- and gamma rays.

 

[The_J]

Pretty interesting and thorough, but is it about radiation poisoning in general, or specifically about receiving enough radiation to kill you in 24 or so hours ?
I understand why we get cancer if we are irradiated, but what I want to dig up info is more about what kills in a matter of hour - Bootstoots says it seems it basically shut down the brain, for example.

The explanation still applies .
While the whole process is e.g. for cancer a matter of weeks and months, it would, in a highly radioactive environment, be a matter of hours.
The radiation makes you basically decompose on molecular level while you're still alive.

To add to the last post, I'm thinking maybe some sort of photosynthesis that uses gamma rays (read: high-energy photons). Essentially have antenna complex molecules that can capture such photons and funnel them into th electron transport chain.

For radiation resistance, maybe the organism can readily metabolize heavy metals and incorporate them into proteins or deposit them like bone minerals.

This actually sounds quite reasonable (under the assumptions which we're making, obviously).

I'd also really like to have them using some sort of magnetic/electric field to funnel radiation toward their feeding organs, and that such fields would seriously compromise human technology - perhaps a form of EMP. That's a point which is pretty vague (how would a biological lifeform be able to create a powerful enough effect ? How easily could technology realistically be vulnerable to such field if it can be shielded against cosmic radiation and the like, which are logically much more powerful ?) and which will be hard to get right, though.

I can not see much possibilites here...as pointed out, if you'd incorporate lots of heavy metals, you might be able to sort of create your own weak field. I don't think it'd be possible to direct this in any way.

That was roughly the idea I was going for (though I'm not knowledgeable enough about, hence my asking, about why kind of radiations would be the most logical to be usable as energy/food

Energy, definitely not food.
As energy would be possible (as already pointed out, photosynthesis is using a sort of radiation to gain energy). For food...food means, you need to re-supply whatever material you've used, because you converted it e.g. into biomass (new cells), or energy (means you broke down something, like sugar, into simpler components). You cannot do this with radiation, unless you think about nuclear fusion, which again is obviously not possible in biological systems.

It seems we can rather easily communicate with man-made space-faring vehicles (like the probes which sent back images from Neptune, or the Mars rover and so on), so I'm not sure a star cosmic rays would actually hamper radio communication in any noticeable capacity (at least, it seems to be easily compensated with 70s technology, so even less of a problem for a close-future one).
I was wondering about something like remotely guiding a robot on the surface of the planet, and could the radioactive background be sufficient to cause interferences and so on.

Solar flares can actually already hamper the communication on earth, but I guess that's then actually a different kind of radiation which causes this (I assume uppi is right about what he's saying).

 

[uppi]

Solar flares can actually already hamper the communication on earth, but I guess that's then actually a different kind of radiation which causes this.

It is not so much the radiation of the solar flare that hampers communication, but the charged particles emitted during a solar flare that disrupt the earth's magnetic field if they hit it. This causes the emission of a lot of radio waves which interfere with communications. The particles arrive a few days after the solar flare, which is why the radiation of the solar flare can be used to predict the disruption of communication a few days later.